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TEX L'il7
4/29/2007 1:16:57 AMThomas Dermody
Hey, where did you go? You didn't leave an e-mail. Hope all of our replies didn't scare you off. You need to get your transmitter working. We will help you to get it working.

T

4/29/2007 9:45:14 AMTex
:Hey, where did you go? You didn't leave an e-mail. Hope all of our replies didn't scare you off. You need to get your transmitter working. We will help you to get it working.
:
:T
I've been busy with my grandson's T-Ball team. With the wires in their original position, except #1 & #2 of the coil switched, my tube voltage readings are:#1)169Vdc, #2)4.8Vac, #3)158Vdc, #4)-.59Vdc, #5)-.43Vdc, #6)124Vac, #7)4.8Vac, #8)0Volts
4/29/2007 9:54:18 AMTex
::Hey, where did you go? You didn't leave an e-mail. Hope all of our replies didn't scare you off. You need to get your transmitter working. We will help you to get it working.
::
::T
:I've been busy with my grandson's T-Ball team. With the wires in their original position, except #1 & #2 of the coil switched, my tube voltage readings are:#1)169Vdc, #2)4.8Vac, #3)158Vdc, #4)-.59Vdc, #5)-.43Vdc, #6)124Vac, #7)4.8Vac, #8)0Volts. I also switced C6 from 150pf to 50pf. My email is jrhradios@yahoo.com
4/30/2007 12:17:06 AMplanigan
::Hey, where did you go? You didn't leave an e-mail. Hope all of our replies didn't scare you off. You need to get your transmitter working. We will help you to get it working.
::
::T
:I've been busy with my grandson's T-Ball team. With the wires in their original position, except #1 & #2 of the coil switched, my tube voltage readings are:#1)169Vdc, #2)4.8Vac, #3)158Vdc, #4)-.59Vdc, #5)-.43Vdc, #6)124Vac, #7)4.8Vac, #8)0Volts


Tex, something is wrong with those readings. Pin 1 is the cathode of the rectifier portion of the tube should be DC but it can not exceed line voltage, actual will be less due to loss in half wave rectification,mine reads 84 VDC. Pin 2 is one side of filiment and should read line voltage (120AC) from it to Pin 7. There should be no reading from either Pin 2 or 7 to ground only between them. Pin 3 should read DC but lower than Pin 1 as it has passed through R3 and the flilter caps. Pin 4 should read about -4VDC as the grid bias. Pin 5 should read 0V with no audio input applied. Pin 6 should read 120 approximately depending on your line voltage as your plate of the rectifier. Pin 8 is 0V. I think you have to re-check the wiring and also check the meter you are using. If your on a 120 AC line voltage you can't read DC volts over that without a step-up transformer. Since your reading at Pin 6 is 124VAC thats right off the transformer and your highest voltage in the set. PL

4/30/2007 10:31:37 AMThomas Dermody
If the rest of his transmitter isn't loading the rectifer properly, due to improper operation, rectifier voltage can exceed line voltage, since line voltage is AC RMS. Actual voltage peaks are much higher, and can show up in an unloaded or slightly loaded filtered rectifier circuit.

T.

4/30/2007 11:50:06 AMThomas Dermody
Also, if you are using a digital voltmeter, or some other really sensitive meter (VTVM), the voltage you detect between pins 2 and 7 and B- (I am assuming that you are referencing to B-, and not to Earth ground) could be capacitive voltage or heater emission voltage. I am assuming that you are using an isolation transformer for the B circuit, and are wiring the heater directly to the AC line or to some other winding. There is capacitive coupling between the primary and the secondary of the transformer, and this can be quite high unless the transformer has two separate bobbins for the windings. Also, especially with such a large heater like the one used in the 117L7/M7, there is some emission between the heater and the cathodes. These two reasons, as well as your using a rather sensitive meter, may be why you detect a small voltage on the heater pins when referencing to B-.

Thomas

5/1/2007 2:57:12 PMTex
I measured all the voltages between the tube pin & common. I checked the voltages with a digital meter and an analog meter. My transformer also has two green wires (12v) which I just left hanging, could that be the problem? I don't have any connection to earth ground unless it is the neutral wire from the wall socket. I made a drawing of my wiring at: http://new.photos.yahoo.com/jrhradios
:Also, if you are using a digital voltmeter, or some other really sensitive meter (VTVM), the voltage you detect between pins 2 and 7 and B- (I am assuming that you are referencing to B-, and not to Earth ground) could be capacitive voltage or heater emission voltage. I am assuming that you are using an isolation transformer for the B circuit, and are wiring the heater directly to the AC line or to some other winding. There is capacitive coupling between the primary and the secondary of the transformer, and this can be quite high unless the transformer has two separate bobbins for the windings. Also, especially with such a large heater like the one used in the 117L7/M7, there is some emission between the heater and the cathodes. These two reasons, as well as your using a rather sensitive meter, may be why you detect a small voltage on the heater pins when referencing to B-.
:
:Thomas
5/1/2007 3:03:40 PMTe
:I measured all the voltages between the tube pin & common. I checked the voltages with a digital meter and an analog meter. My transformer also has two green wires (12v) which I just left hanging, could that be the problem? I don't have any connection to earth ground unless it is the neutral wire from the wall socket. I made a drawing of my wiring at: http://new.photos.yahoo.com/jrhradios
::Also, if you are using a digital voltmeter, or some other really sensitive meter (VTVM), the voltage you detect between pins 2 and 7 and B- (I am assuming that you are referencing to B-, and not to Earth ground) could be capacitive voltage or heater emission voltage. I am assuming that you are using an isolation transformer for the B circuit, and are wiring the heater directly to the AC line or to some other winding. There is capacitive coupling between the primary and the secondary of the transformer, and this can be quite high unless the transformer has two separate bobbins for the windings. Also, especially with such a large heater like the one used in the 117L7/M7, there is some emission between the heater and the cathodes. These two reasons, as well as your using a rather sensitive meter, may be why you detect a small voltage on the heater pins when referencing to B-.
::
::Thomas
5/1/2007 3:04:42 PMTex
::I measured all the voltages between the tube pin & common. I checked the voltages with a digital meter and an analog meter. My transformer also has two green wires (12v) which I just left hanging, could that be the problem? I don't have any connection to earth ground unless it is the neutral wire from the wall socket. I made a drawing of my wiring at: http://new.photos.yahoo.com/jrhradios/#page1
:::Also, if you are using a digital voltmeter, or some other really sensitive meter (VTVM), the voltage you detect between pins 2 and 7 and B- (I am assuming that you are referencing to B-, and not to Earth ground) could be capacitive voltage or heater emission voltage. I am assuming that you are using an isolation transformer for the B circuit, and are wiring the heater directly to the AC line or to some other winding. There is capacitive coupling between the primary and the secondary of the transformer, and this can be quite high unless the transformer has two separate bobbins for the windings. Also, especially with such a large heater like the one used in the 117L7/M7, there is some emission between the heater and the cathodes. These two reasons, as well as your using a rather sensitive meter, may be why you detect a small voltage on the heater pins when referencing to B-.
:::
:::Thomas
5/1/2007 5:36:51 PMEdd
A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
It will be rotating / functioning backwards from the norm.

Referencing this combined schema + your physical wire layout:

http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg

FYI....
*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.

QUESTION.. 1...
Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).

QUESTION.. 2...
Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".

FACT
When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.

Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.

Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
(I been suuuching... I been suuchin.. I been suuchin
......every which a waaaaay....a la Coasters)

If this doesn't result in success, I am tending to think that the coil that you are trying to use is
of such inductive value that, your created signal is much different in frequency output than
expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.


More tricks to come.... if needed...

73's for now
Edd..the other Tejano

5/1/2007 9:19:26 PMThomas Dermody
Now take the 49.3 ohm coil and the 2.1 ohm coil and swap them for eachother. If the unit still doesn't oscillate, swap the wires of one of the coils.

Also, make sure that the outside of the RCA jack connects to B-.

Thomas

5/1/2007 10:54:07 PMLewis L.
I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
Lewis


:A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
:It will be rotating / functioning backwards from the norm.
:
:Referencing this combined schema + your physical wire layout:
:
:http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
:
:FYI....
:*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
:No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
:
:QUESTION.. 1...
:Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
:(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
:
:QUESTION.. 2...
:Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
:It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
:
:FACT
:When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
:actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
:Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
:
:Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
:the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
:
:Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
:(I been suuuching... I been suuchin.. I been suuchin
:......every which a waaaaay....a la Coasters)
:
:If this doesn't result in success, I am tending to think that the coil that you are trying to use is
:of such inductive value that, your created signal is much different in frequency output than
:expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
:
:
:More tricks to come.... if needed...
:
:73's for now
:Edd..the other Tejano
:

5/2/2007 10:55:35 AMTex
I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1

:I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
:Lewis
:
:
::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
::It will be rotating / functioning backwards from the norm.
::
::Referencing this combined schema + your physical wire layout:
::
::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
::
::FYI....
::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
::
::QUESTION.. 1...
::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
::
::QUESTION.. 2...
::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
::
::FACT
::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
::
::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
::
::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
::(I been suuuching... I been suuchin.. I been suuchin
::......every which a waaaaay....a la Coasters)
::
::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
::of such inductive value that, your created signal is much different in frequency output than
::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
::
::
::More tricks to come.... if needed...
::
::73's for now
::Edd..the other Tejano
::

5/2/2007 3:31:03 PMEdd
If I grip & release the 150pf will I get a shock?
Only if your body is externally grounded or you are touching chassis ground with another body part.....another reason I don't like that raw AC to the units filament supply..protection is only as good as isolation...But...I am assuming that you either used a silver mica or possibly a disc ceramic for that function and those can me mighty tiny such that a fat finger might actually touch B+. Soooo you might wrap the cap and its leads in a single wrap of vinyl electrical tape. There would still be enough detuning effect with your gripping the cap body thru the insulative tape covering.

OK ...now after seeing the new voltage readings and a referencing back to the old initial figures that you supplied.

See voltage ref comparisons :
http://img234.imageshack.us/img234/3777/untitledcr2.jpg

I do think that you have a winner, now as compared to the coil connections that you had hooked up before.
My synopsis:

Initially looking at the filament voltages and their comparative readings...well...we might as well disregard them completely, since you do have a cherry red filament on that monster and we are getting derived B+ voltage.
Lets just write off any viable referencing of those voltages as stray or "phantom" readings.

The next thing to consider was the RAW AC voltage on pin 6, so I see that is static from THAT previous time to THIS, and not being pulled down by your having the refrig air set down to 42 degrees or mama cass doing her ironing.

HEY....look at the voltage from the power supply from test 1 until this present test...its lower...meaning that your tube is actually doing something
now. Also reference your plate voltage on pin 3 ..its down also..further confirming some tube activity now with this current hook up.
Now I ask you, isn't it just amazing that those supplied red reference numbers coincide ???

Since you did not have the "freon" test lamp, lets go for another technique. You see that ~220-250 cap that couples into your antenna ...right...well lets just have the end of it that feeds to the antenna disconnected and just then being left as a free lead, with its other lead not being bothered.
What you could try next is substituting your body mass as an antenna. Where you would be not touching any thing grounded and be isolated just as antenna is ....and has to be.
If you will then activate your unit for testing and VERY lightly touch that floating lead with your fingertip, (where the loops and swirls are), if that unit is oscillating that RF should be coupled through that isolation cap and it considers your body mass to be its antenna instead. At the instant of your touching the free floating cap lead there should be the creation of a minute white mark on the fingertip exactly where it touched..and each time that it is repeated. ( Don't worry...be happy...no shockee...no pain ) That would definitively confirm RF being created.
So hunt for your signal, with that radio cranked up for your modulation source, it might just create enough signal to be detected, noting that you CHANGED the terms on the mod control as I said , or else if you turn that control al the way up...like a volume controls action / direction...it would have been grounding out the modulation with no mod AF getting through at all.


Well thats it for now with two other options of RF detection..still in the bag...a diode RF detector... or exposing the coil to permit the coupling of a one turn coil link to light up a low voltage incandescant lamp.

BUT I really think that your unit is ossifrying now, but that you just haven't FOUND the freq that it is outputting on.

73's de Edd


:I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1
:
::I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
::Lewis
::
::
:::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
:::It will be rotating / functioning backwards from the norm.
:::
:::Referencing this combined schema + your physical wire layout:
:::
:::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
:::
:::FYI....
:::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
:::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
:::
:::QUESTION.. 1...
:::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
:::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
:::
:::QUESTION.. 2...
:::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
:::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
:::
:::FACT
:::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
:::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
:::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
:::
:::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
:::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
:::
:::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
:::(I been suuuching... I been suuchin.. I been suuchin
:::......every which a waaaaay....a la Coasters)
:::
:::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
:::of such inductive value that, your created signal is much different in frequency output than
:::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
:::
:::
:::More tricks to come.... if needed...
:::
:::73's for now
:::Edd..the other Tejano
:::

5/2/2007 5:21:02 PMThomas Dermody
An offer: Keep doing what everyone tells you to do, and see if you can get the unit to work. However, if you can't, and you've reached your wit's end, send it to me and I'll get it going for you. All you need to do is pay for postage, which shouldn't be more than $10 each way.

Thomas

5/3/2007 9:31:09 AMTex
I got a NE2 & held the glass part against tube pin #3, but it didn't glow, I also held it against the coils of the osc. I put tape around the 150pf & squeezed & released it, with the receving radio both on a station & not on a station but no swooshing sound. I just don't have the guts to touch the 250pf & antenna, it's not that I don't have confidence in your advice, it's that I don't have enough self confidence to be sure that I would do it according to your instructions.

:If I grip & release the 150pf will I get a shock?
:Only if your body is externally grounded or you are touching chassis ground with another body part.....another reason I don't like that raw AC to the units filament supply..protection is only as good as isolation...But...I am assuming that you either used a silver mica or possibly a disc ceramic for that function and those can me mighty tiny such that a fat finger might actually touch B+. Soooo you might wrap the cap and its leads in a single wrap of vinyl electrical tape. There would still be enough detuning effect with your gripping the cap body thru the insulative tape covering.
:
:OK ...now after seeing the new voltage readings and a referencing back to the old initial figures that you supplied.
:
:See voltage ref comparisons :
:http://img234.imageshack.us/img234/3777/untitledcr2.jpg
:
:I do think that you have a winner, now as compared to the coil connections that you had hooked up before.
:My synopsis:
:
:Initially looking at the filament voltages and their comparative readings...well...we might as well disregard them completely, since you do have a cherry red filament on that monster and we are getting derived B+ voltage.
:Lets just write off any viable referencing of those voltages as stray or "phantom" readings.
:
:The next thing to consider was the RAW AC voltage on pin 6, so I see that is static from THAT previous time to THIS, and not being pulled down by your having the refrig air set down to 42 degrees or mama cass doing her ironing.
:
:HEY....look at the voltage from the power supply from test 1 until this present test...its lower...meaning that your tube is actually doing something
:now. Also reference your plate voltage on pin 3 ..its down also..further confirming some tube activity now with this current hook up.
:Now I ask you, isn't it just amazing that those supplied red reference numbers coincide ???
:
:Since you did not have the "freon" test lamp, lets go for another technique. You see that ~220-250 cap that couples into your antenna ...right...well lets just have the end of it that feeds to the antenna disconnected and just then being left as a free lead, with its other lead not being bothered.
:What you could try next is substituting your body mass as an antenna. Where you would be not touching any thing grounded and be isolated just as antenna is ....and has to be.
:If you will then activate your unit for testing and VERY lightly touch that floating lead with your fingertip, (where the loops and swirls are), if that unit is oscillating that RF should be coupled through that isolation cap and it considers your body mass to be its antenna instead. At the instant of your touching the free floating cap lead there should be the creation of a minute white mark on the fingertip exactly where it touched..and each time that it is repeated. ( Don't worry...be happy...no shockee...no pain ) That would definitively confirm RF being created.
:So hunt for your signal, with that radio cranked up for your modulation source, it might just create enough signal to be detected, noting that you CHANGED the terms on the mod control as I said , or else if you turn that control al the way up...like a volume controls action / direction...it would have been grounding out the modulation with no mod AF getting through at all.
:
:
:Well thats it for now with two other options of RF detection..still in the bag...a diode RF detector... or exposing the coil to permit the coupling of a one turn coil link to light up a low voltage incandescant lamp.
:
:BUT I really think that your unit is ossifrying now, but that you just haven't FOUND the freq that it is outputting on.
:
:73's de Edd
:
:
::I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1
::
:::I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
:::Lewis
:::
:::
::::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
::::It will be rotating / functioning backwards from the norm.
::::
::::Referencing this combined schema + your physical wire layout:
::::
::::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
::::
::::FYI....
::::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
::::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
::::
::::QUESTION.. 1...
::::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
::::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
::::
::::QUESTION.. 2...
::::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
::::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
::::
::::FACT
::::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
::::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
::::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
::::
::::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
::::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
::::
::::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
::::(I been suuuching... I been suuchin.. I been suuchin
::::......every which a waaaaay....a la Coasters)
::::
::::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
::::of such inductive value that, your created signal is much different in frequency output than
::::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
::::
::::
::::More tricks to come.... if needed...
::::
::::73's for now
::::Edd..the other Tejano
::::

5/3/2007 10:38:33 AMplanigan
:I got a NE2 & held the glass part against tube pin #3, but it didn't glow, I also held it against the coils of the osc. I put tape around the 150pf & squeezed & released it, with the receving radio both on a station & not on a station but no swooshing sound. I just don't have the guts to touch the 250pf & antenna, it's not that I don't have confidence in your advice, it's that I don't have enough self confidence to be sure that I would do it according to your instructions.

TEX, there is still something bothering me about the pin voltages. I've got mine working and as I posted before the voltage (pin to chassis/gnd/com except 2 - 7)are 1 - 84VDC, 2 - 118VAC, 3 - 77VDC 4 - -.4VDC, 5 - 0V, 6 - 118VAC, 7 - 118VAC & 8 - 0V. The fact that your getting 4.8 VAC on pins 2 & 7 indicated a "ghost" reading on the DMM as thats the line voltage across the filament and should not return to chassis/gnd/com as it is not directly connected there. But pin 1 is 45V above your line voltage and correspondingly pin 3 is 34V above line voltage (I'm using pin 6 voltage as line but its actually secondary voltage of xfmer). I think Tom posted some info on that that I vaguely understand (RMS, peak to peak) but the operative words were when tube not under load. So if your tube is not under load its not working? Are the electrolitic caps installed with correct polarity? I don't know the answer but maybe someone will chime in. PL
::If I grip & release the 150pf will I get a shock?
::Only if your body is externally grounded or you are touching chassis ground with another body part.....another reason I don't like that raw AC to the units filament supply..protection is only as good as isolation...But...I am assuming that you either used a silver mica or possibly a disc ceramic for that function and those can me mighty tiny such that a fat finger might actually touch B+. Soooo you might wrap the cap and its leads in a single wrap of vinyl electrical tape. There would still be enough detuning effect with your gripping the cap body thru the insulative tape covering.
::
::OK ...now after seeing the new voltage readings and a referencing back to the old initial figures that you supplied.
::
::See voltage ref comparisons :
::http://img234.imageshack.us/img234/3777/untitledcr2.jpg
::
::I do think that you have a winner, now as compared to the coil connections that you had hooked up before.
::My synopsis:
::
::Initially looking at the filament voltages and their comparative readings...well...we might as well disregard them completely, since you do have a cherry red filament on that monster and we are getting derived B+ voltage.
::Lets just write off any viable referencing of those voltages as stray or "phantom" readings.
::
::The next thing to consider was the RAW AC voltage on pin 6, so I see that is static from THAT previous time to THIS, and not being pulled down by your having the refrig air set down to 42 degrees or mama cass doing her ironing.
::
::HEY....look at the voltage from the power supply from test 1 until this present test...its lower...meaning that your tube is actually doing something
::now. Also reference your plate voltage on pin 3 ..its down also..further confirming some tube activity now with this current hook up.
::Now I ask you, isn't it just amazing that those supplied red reference numbers coincide ???
::
::Since you did not have the "freon" test lamp, lets go for another technique. You see that ~220-250 cap that couples into your antenna ...right...well lets just have the end of it that feeds to the antenna disconnected and just then being left as a free lead, with its other lead not being bothered.
::What you could try next is substituting your body mass as an antenna. Where you would be not touching any thing grounded and be isolated just as antenna is ....and has to be.
::If you will then activate your unit for testing and VERY lightly touch that floating lead with your fingertip, (where the loops and swirls are), if that unit is oscillating that RF should be coupled through that isolation cap and it considers your body mass to be its antenna instead. At the instant of your touching the free floating cap lead there should be the creation of a minute white mark on the fingertip exactly where it touched..and each time that it is repeated. ( Don't worry...be happy...no shockee...no pain ) That would definitively confirm RF being created.
::So hunt for your signal, with that radio cranked up for your modulation source, it might just create enough signal to be detected, noting that you CHANGED the terms on the mod control as I said , or else if you turn that control al the way up...like a volume controls action / direction...it would have been grounding out the modulation with no mod AF getting through at all.
::
::
::Well thats it for now with two other options of RF detection..still in the bag...a diode RF detector... or exposing the coil to permit the coupling of a one turn coil link to light up a low voltage incandescant lamp.
::
::BUT I really think that your unit is ossifrying now, but that you just haven't FOUND the freq that it is outputting on.
::
::73's de Edd
::
::
:::I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1
:::
::::I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
::::Lewis
::::
::::
:::::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
:::::It will be rotating / functioning backwards from the norm.
:::::
:::::Referencing this combined schema + your physical wire layout:
:::::
:::::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
:::::
:::::FYI....
:::::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
:::::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
:::::
:::::QUESTION.. 1...
:::::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
:::::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
:::::
:::::QUESTION.. 2...
:::::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
:::::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
:::::
:::::FACT
:::::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
:::::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
:::::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
:::::
:::::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
:::::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
:::::
:::::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
:::::(I been suuuching... I been suuchin.. I been suuchin
:::::......every which a waaaaay....a la Coasters)
:::::
:::::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
:::::of such inductive value that, your created signal is much different in frequency output than
:::::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
:::::
:::::
:::::More tricks to come.... if needed...
:::::
:::::73's for now
:::::Edd..the other Tejano
:::::

5/3/2007 10:40:11 AMplanigan
:I got a NE2 & held the glass part against tube pin #3, but it didn't glow, I also held it against the coils of the osc. I put tape around the 150pf & squeezed & released it, with the receving radio both on a station & not on a station but no swooshing sound. I just don't have the guts to touch the 250pf & antenna, it's not that I don't have confidence in your advice, it's that I don't have enough self confidence to be sure that I would do it according to your instructions.

TEX, there is still something bothering me about the pin voltages. I've got mine working and as I posted before the voltage (pin to chassis/gnd/com except 2 - 7)are 1 - 84VDC, 2 - 118VAC, 3 - 77VDC 4 - -.4VDC, 5 - 0V, 6 - 118VAC, 7 - 118VAC & 8 - 0V. The fact that your getting 4.8 VAC on pins 2 & 7 indicated a "ghost" reading on the DMM as thats the line voltage across the filament and should not return to chassis/gnd/com as it is not directly connected there. But pin 1 is 45V above your line voltage and correspondingly pin 3 is 34V above line voltage (I'm using pin 6 voltage as line but its actually secondary voltage of xfmer). I think Tom posted some info on that that I vaguely understand (RMS, peak to peak) but the operative words were when tube not under load. So if your tube is not under load its not working? Are the electrolitic caps installed with correct polarity? I don't know the answer but maybe someone will chime in. PL


::If I grip & release the 150pf will I get a shock?
::Only if your body is externally grounded or you are touching chassis ground with another body part.....another reason I don't like that raw AC to the units filament supply..protection is only as good as isolation...But...I am assuming that you either used a silver mica or possibly a disc ceramic for that function and those can me mighty tiny such that a fat finger might actually touch B+. Soooo you might wrap the cap and its leads in a single wrap of vinyl electrical tape. There would still be enough detuning effect with your gripping the cap body thru the insulative tape covering.
::
::OK ...now after seeing the new voltage readings and a referencing back to the old initial figures that you supplied.
::
::See voltage ref comparisons :
::http://img234.imageshack.us/img234/3777/untitledcr2.jpg
::
::I do think that you have a winner, now as compared to the coil connections that you had hooked up before.
::My synopsis:
::
::Initially looking at the filament voltages and their comparative readings...well...we might as well disregard them completely, since you do have a cherry red filament on that monster and we are getting derived B+ voltage.
::Lets just write off any viable referencing of those voltages as stray or "phantom" readings.
::
::The next thing to consider was the RAW AC voltage on pin 6, so I see that is static from THAT previous time to THIS, and not being pulled down by your having the refrig air set down to 42 degrees or mama cass doing her ironing.
::
::HEY....look at the voltage from the power supply from test 1 until this present test...its lower...meaning that your tube is actually doing something
::now. Also reference your plate voltage on pin 3 ..its down also..further confirming some tube activity now with this current hook up.
::Now I ask you, isn't it just amazing that those supplied red reference numbers coincide ???
::
::Since you did not have the "freon" test lamp, lets go for another technique. You see that ~220-250 cap that couples into your antenna ...right...well lets just have the end of it that feeds to the antenna disconnected and just then being left as a free lead, with its other lead not being bothered.
::What you could try next is substituting your body mass as an antenna. Where you would be not touching any thing grounded and be isolated just as antenna is ....and has to be.
::If you will then activate your unit for testing and VERY lightly touch that floating lead with your fingertip, (where the loops and swirls are), if that unit is oscillating that RF should be coupled through that isolation cap and it considers your body mass to be its antenna instead. At the instant of your touching the free floating cap lead there should be the creation of a minute white mark on the fingertip exactly where it touched..and each time that it is repeated. ( Don't worry...be happy...no shockee...no pain ) That would definitively confirm RF being created.
::So hunt for your signal, with that radio cranked up for your modulation source, it might just create enough signal to be detected, noting that you CHANGED the terms on the mod control as I said , or else if you turn that control al the way up...like a volume controls action / direction...it would have been grounding out the modulation with no mod AF getting through at all.
::
::
::Well thats it for now with two other options of RF detection..still in the bag...a diode RF detector... or exposing the coil to permit the coupling of a one turn coil link to light up a low voltage incandescant lamp.
::
::BUT I really think that your unit is ossifrying now, but that you just haven't FOUND the freq that it is outputting on.
::
::73's de Edd
::
::
:::I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1
:::
::::I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
::::Lewis
::::
::::
:::::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
:::::It will be rotating / functioning backwards from the norm.
:::::
:::::Referencing this combined schema + your physical wire layout:
:::::
:::::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
:::::
:::::FYI....
:::::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
:::::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
:::::
:::::QUESTION.. 1...
:::::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
:::::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
:::::
:::::QUESTION.. 2...
:::::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
:::::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
:::::
:::::FACT
:::::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
:::::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
:::::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
:::::
:::::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
:::::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
:::::
:::::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
:::::(I been suuuching... I been suuchin.. I been suuchin
:::::......every which a waaaaay....a la Coasters)
:::::
:::::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
:::::of such inductive value that, your created signal is much different in frequency output than
:::::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
:::::
:::::
:::::More tricks to come.... if needed...
:::::
:::::73's for now
:::::Edd..the other Tejano
:::::

5/4/2007 1:12:20 PMRadiodoc
Planigan,

Did you happen to measure the resistance of the coil you are using in your L'il7 so it could be compared to the coil Tex is using to determine which winding is used in the plate circuit and which one is used in the grid circuit of the tube.

Radiodoc

::I got a NE2 & held the glass part against tube pin #3, but it didn't glow, I also held it against the coils of the osc. I put tape around the 150pf & squeezed & released it, with the receving radio both on a station & not on a station but no swooshing sound. I just don't have the guts to touch the 250pf & antenna, it's not that I don't have confidence in your advice, it's that I don't have enough self confidence to be sure that I would do it according to your instructions.
:
:
:
: TEX, there is still something bothering me about the pin voltages. I've got mine working and as I posted before the voltage (pin to chassis/gnd/com except 2 - 7)are 1 - 84VDC, 2 - 118VAC, 3 - 77VDC 4 - -.4VDC, 5 - 0V, 6 - 118VAC, 7 - 118VAC & 8 - 0V. The fact that your getting 4.8 VAC on pins 2 & 7 indicated a "ghost" reading on the DMM as thats the line voltage across the filament and should not return to chassis/gnd/com as it is not directly connected there. But pin 1 is 45V above your line voltage and correspondingly pin 3 is 34V above line voltage (I'm using pin 6 voltage as line but its actually secondary voltage of xfmer). I think Tom posted some info on that that I vaguely understand (RMS, peak to peak) but the operative words were when tube not under load. So if your tube is not under load its not working? Are the electrolitic caps installed with correct polarity? I don't know the answer but maybe someone will chime in. PL
:
:
:
:
:::If I grip & release the 150pf will I get a shock?
:::Only if your body is externally grounded or you are touching chassis ground with another body part.....another reason I don't like that raw AC to the units filament supply..protection is only as good as isolation...But...I am assuming that you either used a silver mica or possibly a disc ceramic for that function and those can me mighty tiny such that a fat finger might actually touch B+. Soooo you might wrap the cap and its leads in a single wrap of vinyl electrical tape. There would still be enough detuning effect with your gripping the cap body thru the insulative tape covering.
:::
:::OK ...now after seeing the new voltage readings and a referencing back to the old initial figures that you supplied.
:::
:::See voltage ref comparisons :
:::http://img234.imageshack.us/img234/3777/untitledcr2.jpg
:::
:::I do think that you have a winner, now as compared to the coil connections that you had hooked up before.
:::My synopsis:
:::
:::Initially looking at the filament voltages and their comparative readings...well...we might as well disregard them completely, since you do have a cherry red filament on that monster and we are getting derived B+ voltage.
:::Lets just write off any viable referencing of those voltages as stray or "phantom" readings.
:::
:::The next thing to consider was the RAW AC voltage on pin 6, so I see that is static from THAT previous time to THIS, and not being pulled down by your having the refrig air set down to 42 degrees or mama cass doing her ironing.
:::
:::HEY....look at the voltage from the power supply from test 1 until this present test...its lower...meaning that your tube is actually doing something
:::now. Also reference your plate voltage on pin 3 ..its down also..further confirming some tube activity now with this current hook up.
:::Now I ask you, isn't it just amazing that those supplied red reference numbers coincide ???
:::
:::Since you did not have the "freon" test lamp, lets go for another technique. You see that ~220-250 cap that couples into your antenna ...right...well lets just have the end of it that feeds to the antenna disconnected and just then being left as a free lead, with its other lead not being bothered.
:::What you could try next is substituting your body mass as an antenna. Where you would be not touching any thing grounded and be isolated just as antenna is ....and has to be.
:::If you will then activate your unit for testing and VERY lightly touch that floating lead with your fingertip, (where the loops and swirls are), if that unit is oscillating that RF should be coupled through that isolation cap and it considers your body mass to be its antenna instead. At the instant of your touching the free floating cap lead there should be the creation of a minute white mark on the fingertip exactly where it touched..and each time that it is repeated. ( Don't worry...be happy...no shockee...no pain ) That would definitively confirm RF being created.
:::So hunt for your signal, with that radio cranked up for your modulation source, it might just create enough signal to be detected, noting that you CHANGED the terms on the mod control as I said , or else if you turn that control al the way up...like a volume controls action / direction...it would have been grounding out the modulation with no mod AF getting through at all.
:::
:::
:::Well thats it for now with two other options of RF detection..still in the bag...a diode RF detector... or exposing the coil to permit the coupling of a one turn coil link to light up a low voltage incandescant lamp.
:::
:::BUT I really think that your unit is ossifrying now, but that you just haven't FOUND the freq that it is outputting on.
:::
:::73's de Edd
:::
:::
::::I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1
::::
:::::I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
:::::Lewis
:::::
:::::
::::::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
::::::It will be rotating / functioning backwards from the norm.
::::::
::::::Referencing this combined schema + your physical wire layout:
::::::
::::::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
::::::
::::::FYI....
::::::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
::::::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
::::::
::::::QUESTION.. 1...
::::::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
::::::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
::::::
::::::QUESTION.. 2...
::::::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
::::::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
::::::
::::::FACT
::::::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
::::::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
::::::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
::::::
::::::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
::::::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
::::::
::::::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
::::::(I been suuuching... I been suuchin.. I been suuchin
::::::......every which a waaaaay....a la Coasters)
::::::
::::::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
::::::of such inductive value that, your created signal is much different in frequency output than
::::::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
::::::
::::::
::::::More tricks to come.... if needed...
::::::
::::::73's for now
::::::Edd..the other Tejano
::::::

5/3/2007 11:29:10 AMThomas Dermody
You aren't going to get a shock. Your unit is fully isolated. Sit on carpeting or hardwood on a dry day. Not that I guarantee this, but you can stick the hot wire of an AC cord in your mouth if you're sitting on carpeting or hardwood (especially when wearing clothing). Your fingers are much less sensitive than your mouth. I have only had trouble on carpeting or hardwood when it was either really humid or my mother was running the sprinkler outside, and the humidity was coming through the window. When I was very young, I had a phonograph that she gave to me that was her's when she was young. It had a band-aid on the tone arm to keep you from getting shocks, since the chassis was connected to the line cord through a condenser. I removed the band aid because I didn't like it. The phonograph would then give me shocks outside, on concrete floors, or if operated right next to a window where a sprinkler was being operated outside.

With your circuit being isolated from the line, you're not going to get a shock from it unless there's a defect in the power transformer. Connect your meter between B- and a water pipe. Set it to 250 volts AC. See any voltage? Flip the plug. See any voltage? You shouldn't see any, or if you do see any, it should be extremely small. This won't shock you when you're sitting on carpeting or hardwood. B+ isn't any more likely to shock you, either. Just don't touch B+ and B- at the same time, because they will shock you.

Thomas

5/3/2007 1:39:15 PMTex
I disconnected the wire from the 250pf cap & the antenna, plugged the transmitter in, and lightly touched the end of the loose wire of the cap. It didn't make a white mark.

If I grip & release the 150pf will I get a shock?
:Only if your body is externally grounded or you are touching chassis ground with another body part.....another reason I don't like that raw AC to the units filament supply..protection is only as good as isolation...But...I am assuming that you either used a silver mica or possibly a disc ceramic for that function and those can me mighty tiny such that a fat finger might actually touch B+. Soooo you might wrap the cap and its leads in a single wrap of vinyl electrical tape. There would still be enough detuning effect with your gripping the cap body thru the insulative tape covering.
:
:OK ...now after seeing the new voltage readings and a referencing back to the old initial figures that you supplied.
:
:See voltage ref comparisons :
:http://img234.imageshack.us/img234/3777/untitledcr2.jpg
:
:I do think that you have a winner, now as compared to the coil connections that you had hooked up before.
:My synopsis:
:
:Initially looking at the filament voltages and their comparative readings...well...we might as well disregard them completely, since you do have a cherry red filament on that monster and we are getting derived B+ voltage.
:Lets just write off any viable referencing of those voltages as stray or "phantom" readings.
:
:The next thing to consider was the RAW AC voltage on pin 6, so I see that is static from THAT previous time to THIS, and not being pulled down by your having the refrig air set down to 42 degrees or mama cass doing her ironing.
:
:HEY....look at the voltage from the power supply from test 1 until this present test...its lower...meaning that your tube is actually doing something
:now. Also reference your plate voltage on pin 3 ..its down also..further confirming some tube activity now with this current hook up.
:Now I ask you, isn't it just amazing that those supplied red reference numbers coincide ???
:
:Since you did not have the "freon" test lamp, lets go for another technique. You see that ~220-250 cap that couples into your antenna ...right...well lets just have the end of it that feeds to the antenna disconnected and just then being left as a free lead, with its other lead not being bothered.
:What you could try next is substituting your body mass as an antenna. Where you would be not touching any thing grounded and be isolated just as antenna is ....and has to be.
:If you will then activate your unit for testing and VERY lightly touch that floating lead with your fingertip, (where the loops and swirls are), if that unit is oscillating that RF should be coupled through that isolation cap and it considers your body mass to be its antenna instead. At the instant of your touching the free floating cap lead there should be the creation of a minute white mark on the fingertip exactly where it touched..and each time that it is repeated. ( Don't worry...be happy...no shockee...no pain ) That would definitively confirm RF being created.
:So hunt for your signal, with that radio cranked up for your modulation source, it might just create enough signal to be detected, noting that you CHANGED the terms on the mod control as I said , or else if you turn that control al the way up...like a volume controls action / direction...it would have been grounding out the modulation with no mod AF getting through at all.
:
:
:Well thats it for now with two other options of RF detection..still in the bag...a diode RF detector... or exposing the coil to permit the coupling of a one turn coil link to light up a low voltage incandescant lamp.
:
:BUT I really think that your unit is ossifrying now, but that you just haven't FOUND the freq that it is outputting on.
:
:73's de Edd
:
:
::I don't have a NE2 bulb. I don't understand 60~hum. I'm using a transistor radio with earphone jack as the input. If I grip & release the 150pf will I get a shock? I removed the wire from coil #3 (the one that goes to the + side of the electrolytic)& put it on coil #4. I removed the wires from coil #4(the ones that go to the ant. & tube pin #3) & put them on coil #3. The voltages are (from pin to common): Tube pin #1 161Vdc, #2 13.7Vdc, #3 153Vdc, #4 -.5Vdc, #5 -.5Vdc, #6 124Vac, #7 11.3Vdc, #8 0V, tube pin #2 to #7 120Vac. Photos of top & bottom of transmitter: http://new.photos.yahoo.com/jrhradios/#page1
::
:::I agree with Edd, the thing has worked at some time what with all the phase swapping and the coil swapping that has been done, it is oscillating somewhere outside of the broacast band. A VTVM or a DMM should show a negative Voltage on the grid when the tube is oscillating, should it not??
:::Lewis
:::
:::
::::A cursory examination reveals all to be in order with the exception of your mis- wire of the modulation control pot..as depicted from your rear view of the unit..
::::It will be rotating / functioning backwards from the norm.
::::
::::Referencing this combined schema + your physical wire layout:
::::
::::http://img114.imageshack.us/img114/1986/lil7layoutandschemacombsi0.jpg
::::
::::FYI....
::::*** My transformer also has two green wires (12v) which I just left hanging, could that be the problem? ***
::::No problemo with that at all ....however, had that been my construction project...I certainly think that I would have opted to use that 12 VAC winding to serve as filament supply so that I could use a less pricey tube instead..say a 12V6 or 12AQ5 AF output tube (normally) and a separate silicon diode for the power supply . Instead of shelling out for that pricier, and progressively harder to find tube that was specified.
::::
::::QUESTION.. 1...
::::Did you use my suggested procedure of the utilization of a NE-2 lamps with its glass envelope brought up to and touching the plate pin of the tube, (or the windings of your osc coil...but I think your coil unit might be in a metal can ??) while being held by the lamps wire leads. This should make an orange glow in the presence of RF being generated by your unit.
::::(FIO...BTW...if in testing a common osc circuit of a 6BE6 / 6SA7 in a common radio....too weak to use the same procedure).
::::
::::QUESTION.. 2...
::::Did you use either an AF modulated signal input to your xmitter or my tip of injecting 60~ hum for use as your modulating agent, ?
::::It is somewhat challenging in detecting an unmodulated RF carrier on the AM band while tuning across a wide spectrum with your "search" receiver...somewhat akin to a differentiation between "quiet" and "quieter".
::::
::::FACT
::::When you tune your monitoring receiver into what you THINK is your outputted RF signal, you can take your thumb-index finger combo and grip--release the 150 pf fixed tuning cap and cause a "swishing" noise in the receiver as its frequecy is "squegged" by that
::::actions detuning effect . Same is true of the coil...'cept I think that your pic showed it to be non accessile to do same.
::::Heck...when you get down to it..... you could even whack that 150 pf cap with a small plastic screwdriver handle and create a small freq shift such as to replicate that same noise, in a weaker manner, on the receiver.
::::
::::Should no glory be found in Muddville, by now, ( T-ball !) after a thorough searching for your RF signal without result, there is the next possibility of
::::the unit not being oscillating by virtue of improper phase of feed back of the two coil windings of your transformer. So, using the pictoral that you supplied, (and I re-referenced in my combined drawings) power down the set and lift away the single B+ wire going to your marked terminal 3 of the coil. Then pull off both the 250 pf ant coupling cap and the plate wire that went to terminal 4 of the coil. Then you transpose the connections, with the plate wire and the ant coupling cap going to coil term 3 and the sole B+ supply wire feeding coil terminal 4.
::::
::::Then you do a RF check as mentioned before and a seeking for your RF signal on a receiver.
::::(I been suuuching... I been suuchin.. I been suuchin
::::......every which a waaaaay....a la Coasters)
::::
::::If this doesn't result in success, I am tending to think that the coil that you are trying to use is
::::of such inductive value that, your created signal is much different in frequency output than
::::expected. E.G.....its "wukkin"....you just have yet to explore the frequency specrum that it is outputting on.
::::
::::
::::More tricks to come.... if needed...
::::
::::73's for now
::::Edd..the other Tejano
::::

5/3/2007 5:52:26 PMEdd

"AWRIGHT", already..so we're not quite ready to nominate you for the Bronze star for bravery...but....what the hey ..LOL

Meaning....OK on the "no mini-micro RF burn" situation, and after looking at the schema and that B+ filter / dropping resistor value of a high 10 K I can see only a RF power capability of the unit in the order of one tenth watt being attainable thru the power supply, the way that 10 K resistor chokes it down, so that would not be enough to get that probable level of effective created RF.

Plus after reviewing planigans data, which I just remembered him including in yet a separate tread of this common topic.
Ref new comparisons:

http://img455.imageshack.us/img455/9207/liltextroubleshootingvodc6.jpg

YOU are having quite a high developed raw B+ in comparison to his voltage ...your ~161 Vdc versus his ~84 Vdc...which I normally
would expect the higher voltage level that you are developing to be that voltage one expects to be seen by rectification by a solid
state rectifier device, and his lower 84 volts to be that derived from a somewhat weakened rectifier tube.
In either case BOTH of your units seem to now be loading down the power supply......pulling current.... such that the produced voltage drop is in the order of -5% for your unit while being -9% for p's.

Its certainly not written in stone that one has to use the EXACT ***total parts package when building up that circuit but its variance can skew the enacting of like voltage comparisons between units.
*** That's the fun of utilizing what you have on hand if they can be compatible.

Also I still am still wondering about the source of supply of that RF coil that you are using. If it is in a large cased shield housing, it reminds me of some old units used in RF circuitry of WW1 tank receivers...basically meaning..... that I am unsure of its actual inductive values and intended design frequency of use. Also since you mentioned access to the coils, as you apparently have exposed
them for viewing, any chance of that unit having any internal fixed capacitors shunting those windings?

Finally , I am almost ready to include in this weekends activities, the pulling out a 6V6 , a tube socket, and two lab power supplies and the few parts to hay-wire up that circuitry for evaluation.

I tend to question the way the cathode of the pentode is wired / treated in that shown application.

The only other thing that comes to mind now is possibly your taking another ~10 K resistor and shunting that B+ filter resistor to get the
available B+ supplied to the plate circuitry up a bit to see if either it ups the very weak RF activity present now or if it is enough to
activate stronger oscillation.


Yet another re-draft of the RF and the Power supply areas, such as I would typically make them up..also with tube pin to functions referencing:

http://img49.imageshack.us/img49/1423/little007redraftschemajpe5.jpg
J-pegged...soooo mag it up to size...

73's de Edd

5/3/2007 9:19:01 PMTex
I added another 10k resistor along side the other one, the voltage on tube pin #3 is now only 4.8dc, #5 is -.4dc,#7 is 5.5dc, the others seemed to stay about the same. The coil is the Miller RF-72, it isn't in a case. I have a picture of the coil & of the data sheet that came with the coil at: http://new.photos.yahoo.com/jrhradios

:
:"AWRIGHT", already..so we're not quite ready to nominate you for the Bronze star for bravery...but....what the hey ..LOL
:
:Meaning....OK on the "no mini-micro RF burn" situation, and after looking at the schema and that B+ filter / dropping resistor value of a high 10 K I can see only a RF power capability of the unit in the order of one tenth watt being attainable thru the power supply, the way that 10 K resistor chokes it down, so that would not be enough to get that probable level of effective created RF.
:
:Plus after reviewing planigans data, which I just remembered him including in yet a separate tread of this common topic.
:Ref new comparisons:
:
:http://img455.imageshack.us/img455/9207/liltextroubleshootingvodc6.jpg
:
:YOU are having quite a high developed raw B+ in comparison to his voltage ...your ~161 Vdc versus his ~84 Vdc...which I normally
:would expect the higher voltage level that you are developing to be that voltage one expects to be seen by rectification by a solid
:state rectifier device, and his lower 84 volts to be that derived from a somewhat weakened rectifier tube.
:In either case BOTH of your units seem to now be loading down the power supply......pulling current.... such that the produced voltage drop is in the order of -5% for your unit while being -9% for p's.
:
:Its certainly not written in stone that one has to use the EXACT ***total parts package when building up that circuit but its variance can skew the enacting of like voltage comparisons between units.
:*** That's the fun of utilizing what you have on hand if they can be compatible.
:
:Also I still am still wondering about the source of supply of that RF coil that you are using. If it is in a large cased shield housing, it reminds me of some old units used in RF circuitry of WW1 tank receivers...basically meaning..... that I am unsure of its actual inductive values and intended design frequency of use. Also since you mentioned access to the coils, as you apparently have exposed
:them for viewing, any chance of that unit having any internal fixed capacitors shunting those windings?
:
:Finally , I am almost ready to include in this weekends activities, the pulling out a 6V6 , a tube socket, and two lab power supplies and the few parts to hay-wire up that circuitry for evaluation.
:
:I tend to question the way the cathode of the pentode is wired / treated in that shown application.
:
:The only other thing that comes to mind now is possibly your taking another ~10 K resistor and shunting that B+ filter resistor to get the
:available B+ supplied to the plate circuitry up a bit to see if either it ups the very weak RF activity present now or if it is enough to
:activate stronger oscillation.
:
:
:Yet another re-draft of the RF and the Power supply areas, such as I would typically make them up..also with tube pin to functions referencing:
:
:http://img49.imageshack.us/img49/1423/little007redraftschemajpe5.jpg
:J-pegged...soooo mag it up to size...
:
:73's de Edd

5/3/2007 11:03:20 PMEdd
Whooooaaaa there, now ...the key words possibly being "along side the other one" and with the accompanying voltage readings given as now being
present on pin 3 would tend to infer that the originating DC voltage received from pin 1 is going through the original R3 (10K) and then into the
new 10K and then to over to the original R3's juncture at C4. Thus, a series connection of the resistorswas made. That would be giving less voltage
available to the plate circuitry than was previously supplied to it. Which your voltage is now reading.However, that is MUCH lower than I typically
would have expected.
The desired connection is a parallel connection, where the new 10K shunts across the original R3 and the load is shared between the side by side
parts such that the combined pairs resistance is then 5k and a bit heftier voltage drive is sent to the plate circuitry, the B+ enters the side by
side left sets of leads of the resistive pair and then exits over to the like tandem and the voltage then is at C4 electrolytic and on over as the
plate supply...hopefully to get the desired result.
Confirm the desired hook up now,

73's de Edd

:I added another 10k resistor along side the other one, the voltage on tube pin #3 is now only 4.8dc, #5 is -.4dc,#7 is 5.5dc, the others seemed to stay about the same. The coil is the Miller RF-72, it isn't in a case. I have a picture of the coil & of the data sheet that came with the coil at: http://new.photos.yahoo.com/jrhradios
:
::
::"AWRIGHT", already..so we're not quite ready to nominate you for the Bronze star for bravery...but....what the hey ..LOL
::
::Meaning....OK on the "no mini-micro RF burn" situation, and after looking at the schema and that B+ filter / dropping resistor value of a high 10 K I can see only a RF power capability of the unit in the order of one tenth watt being attainable thru the power supply, the way that 10 K resistor chokes it down, so that would not be enough to get that probable level of effective created RF.
::
::Plus after reviewing planigans data, which I just remembered him including in yet a separate tread of this common topic.
::Ref new comparisons:
::
::http://img455.imageshack.us/img455/9207/liltextroubleshootingvodc6.jpg
::
::YOU are having quite a high developed raw B+ in comparison to his voltage ...your ~161 Vdc versus his ~84 Vdc...which I normally
::would expect the higher voltage level that you are developing to be that voltage one expects to be seen by rectification by a solid
::state rectifier device, and his lower 84 volts to be that derived from a somewhat weakened rectifier tube.
::In either case BOTH of your units seem to now be loading down the power supply......pulling current.... such that the produced voltage drop is in the order of -5% for your unit while being -9% for p's.
::
::Its certainly not written in stone that one has to use the EXACT ***total parts package when building up that circuit but its variance can skew the enacting of like voltage comparisons between units.
::*** That's the fun of utilizing what you have on hand if they can be compatible.
::
::Also I still am still wondering about the source of supply of that RF coil that you are using. If it is in a large cased shield housing, it reminds me of some old units used in RF circuitry of WW1 tank receivers...basically meaning..... that I am unsure of its actual inductive values and intended design frequency of use. Also since you mentioned access to the coils, as you apparently have exposed
::them for viewing, any chance of that unit having any internal fixed capacitors shunting those windings?
::
::Finally , I am almost ready to include in this weekends activities, the pulling out a 6V6 , a tube socket, and two lab power supplies and the few parts to hay-wire up that circuitry for evaluation.
::
::I tend to question the way the cathode of the pentode is wired / treated in that shown application.
::
::The only other thing that comes to mind now is possibly your taking another ~10 K resistor and shunting that B+ filter resistor to get the
::available B+ supplied to the plate circuitry up a bit to see if either it ups the very weak RF activity present now or if it is enough to
::activate stronger oscillation.
::
::
::Yet another re-draft of the RF and the Power supply areas, such as I would typically make them up..also with tube pin to functions referencing:
::
::http://img49.imageshack.us/img49/1423/little007redraftschemajpe5.jpg
::J-pegged...soooo mag it up to size...
::
::73's de Edd

5/4/2007 8:13:02 AMTex
I took a wire that has an alligator clip on each end I attached one alligator clip to one end of the original 10k, the other alligator clip attached to one end of another 10k. I took another wire that has an alligator clip on each end and attached it to the other end of the original 10k with the other alligator clip attached to the other end of the new 10k. The two 10k resistors are side by side not end to end. I beleive they are parallel not in series.

hooooaaaa there, now ...the key words possibly being "along side the other one" and with the accompanying voltage readings given as now being
:present on pin 3 would tend to infer that the originating DC voltage received from pin 1 is going through the original R3 (10K) and then into the
:new 10K and then to over to the original R3's juncture at C4. Thus, a series connection of the resistorswas made. That would be giving less voltage
:available to the plate circuitry than was previously supplied to it. Which your voltage is now reading.However, that is MUCH lower than I typically
:would have expected.
:The desired connection is a parallel connection, where the new 10K shunts across the original R3 and the load is shared between the side by side
:parts such that the combined pairs resistance is then 5k and a bit heftier voltage drive is sent to the plate circuitry, the B+ enters the side by
:side left sets of leads of the resistive pair and then exits over to the like tandem and the voltage then is at C4 electrolytic and on over as the
:plate supply...hopefully to get the desired result.
:Confirm the desired hook up now,
:
:73's de Edd
:
::I added another 10k resistor along side the other one, the voltage on tube pin #3 is now only 4.8dc, #5 is -.4dc,#7 is 5.5dc, the others seemed to stay about the same. The coil is the Miller RF-72, it isn't in a case. I have a picture of the coil & of the data sheet that came with the coil at: http://new.photos.yahoo.com/jrhradios
::
:::
:::"AWRIGHT", already..so we're not quite ready to nominate you for the Bronze star for bravery...but....what the hey ..LOL
:::
:::Meaning....OK on the "no mini-micro RF burn" situation, and after looking at the schema and that B+ filter / dropping resistor value of a high 10 K I can see only a RF power capability of the unit in the order of one tenth watt being attainable thru the power supply, the way that 10 K resistor chokes it down, so that would not be enough to get that probable level of effective created RF.
:::
:::Plus after reviewing planigans data, which I just remembered him including in yet a separate tread of this common topic.
:::Ref new comparisons:
:::
:::http://img455.imageshack.us/img455/9207/liltextroubleshootingvodc6.jpg
:::
:::YOU are having quite a high developed raw B+ in comparison to his voltage ...your ~161 Vdc versus his ~84 Vdc...which I normally
:::would expect the higher voltage level that you are developing to be that voltage one expects to be seen by rectification by a solid
:::state rectifier device, and his lower 84 volts to be that derived from a somewhat weakened rectifier tube.
:::In either case BOTH of your units seem to now be loading down the power supply......pulling current.... such that the produced voltage drop is in the order of -5% for your unit while being -9% for p's.
:::
:::Its certainly not written in stone that one has to use the EXACT ***total parts package when building up that circuit but its variance can skew the enacting of like voltage comparisons between units.
:::*** That's the fun of utilizing what you have on hand if they can be compatible.
:::
:::Also I still am still wondering about the source of supply of that RF coil that you are using. If it is in a large cased shield housing, it reminds me of some old units used in RF circuitry of WW1 tank receivers...basically meaning..... that I am unsure of its actual inductive values and intended design frequency of use. Also since you mentioned access to the coils, as you apparently have exposed
:::them for viewing, any chance of that unit having any internal fixed capacitors shunting those windings?
:::
:::Finally , I am almost ready to include in this weekends activities, the pulling out a 6V6 , a tube socket, and two lab power supplies and the few parts to hay-wire up that circuitry for evaluation.
:::
:::I tend to question the way the cathode of the pentode is wired / treated in that shown application.
:::
:::The only other thing that comes to mind now is possibly your taking another ~10 K resistor and shunting that B+ filter resistor to get the
:::available B+ supplied to the plate circuitry up a bit to see if either it ups the very weak RF activity present now or if it is enough to
:::activate stronger oscillation.
:::
:::
:::Yet another re-draft of the RF and the Power supply areas, such as I would typically make them up..also with tube pin to functions referencing:
:::
:::http://img49.imageshack.us/img49/1423/little007redraftschemajpe5.jpg
:::J-pegged...soooo mag it up to size...
:::
:::73's de Edd

5/4/2007 10:54:23 AMEdd
You are definitely correct there, just wanted to positively confirm....plus my being blind....that voltage on the plate which was listed as 153 VDC should have went up , yet you give 4.8 Vdc as being its present reading ?
To clear that up, hows about lifting one test lead to revert the circuit to its initial state and meter both the raw B+ at pin 1 and the plate voltage at pin 3 to reconfirm that they are at their initial values of ~161 Vdc at pin 1 and ~153Dvc at pin 3. If those initial voltage readings are not replicated, confirnm that you are establishing a good ground connection with the meterings negative probe...or not accidentally being in the meters AC mode. BTW..FIO..what meter are we using, DVM,VTVM,FET-VM, TVOM..or certainly..or hopefully
not a common VOM.....(merely, in respect to capability of taking effectual 1st grid readings.)
(Disregard further filament readings on pins 2 and 7, as they are of no concern..the filament is lighting up...right).
Next, hows about reinstating the one loose clip lead to get the R3 "cluster" back so that you can confirm a reading again, if it is still at that low value, run the modulation control back max CCW / to minumum and then re confirm the plate reading to see if there is a variance to that plates voltage reading.
Those are the only things that come to mind at the present , in a logical accounting for the drastic variance of the readings.

73's de Edd

:I took a wire that has an alligator clip on each end I attached one alligator clip to one end of the original 10k, the other alligator clip attached to one end of another 10k. I took another wire that has an alligator clip on each end and attached it to the other end of the original 10k with the other alligator clip attached to the other end of the new 10k. The two 10k resistors are side by side not end to end. I beleive they are parallel not in series.
:
:hooooaaaa there, now ...the key words possibly being "along side the other one" and with the accompanying voltage readings given as now being
::present on pin 3 would tend to infer that the originating DC voltage received from pin 1 is going through the original R3 (10K) and then into the
::new 10K and then to over to the original R3's juncture at C4. Thus, a series connection of the resistorswas made. That would be giving less voltage
::available to the plate circuitry than was previously supplied to it. Which your voltage is now reading.However, that is MUCH lower than I typically
::would have expected.
::The desired connection is a parallel connection, where the new 10K shunts across the original R3 and the load is shared between the side by side
::parts such that the combined pairs resistance is then 5k and a bit heftier voltage drive is sent to the plate circuitry, the B+ enters the side by
::side left sets of leads of the resistive pair and then exits over to the like tandem and the voltage then is at C4 electrolytic and on over as the
::plate supply...hopefully to get the desired result.
::Confirm the desired hook up now,
::
::73's de Edd
::
:::I added another 10k resistor along side the other one, the voltage on tube pin #3 is now only 4.8dc, #5 is -.4dc,#7 is 5.5dc, the others seemed to stay about the same. The coil is the Miller RF-72, it isn't in a case. I have a picture of the coil & of the data sheet that came with the coil at: http://new.photos.yahoo.com/jrhradios
:::
::::
::::"AWRIGHT", already..so we're not quite ready to nominate you for the Bronze star for bravery...but....what the hey ..LOL
::::
::::Meaning....OK on the "no mini-micro RF burn" situation, and after looking at the schema and that B+ filter / dropping resistor value of a high 10 K I can see only a RF power capability of the unit in the order of one tenth watt being attainable thru the power supply, the way that 10 K resistor chokes it down, so that would not be enough to get that probable level of effective created RF.
::::
::::Plus after reviewing planigans data, which I just remembered him including in yet a separate tread of this common topic.
::::Ref new comparisons:
::::
::::http://img455.imageshack.us/img455/9207/liltextroubleshootingvodc6.jpg
::::
::::YOU are having quite a high developed raw B+ in comparison to his voltage ...your ~161 Vdc versus his ~84 Vdc...which I normally
::::would expect the higher voltage level that you are developing to be that voltage one expects to be seen by rectification by a solid
::::state rectifier device, and his lower 84 volts to be that derived from a somewhat weakened rectifier tube.
::::In either case BOTH of your units seem to now be loading down the power supply......pulling current.... such that the produced voltage drop is in the order of -5% for your unit while being -9% for p's.
::::
::::Its certainly not written in stone that one has to use the EXACT ***total parts package when building up that circuit but its variance can skew the enacting of like voltage comparisons between units.
::::*** That's the fun of utilizing what you have on hand if they can be compatible.
::::
::::Also I still am still wondering about the source of supply of that RF coil that you are using. If it is in a large cased shield housing, it reminds me of some old units used in RF circuitry of WW1 tank receivers...basically meaning..... that I am unsure of its actual inductive values and intended design frequency of use. Also since you mentioned access to the coils, as you apparently have exposed
::::them for viewing, any chance of that unit having any internal fixed capacitors shunting those windings?
::::
::::Finally , I am almost ready to include in this weekends activities, the pulling out a 6V6 , a tube socket, and two lab power supplies and the few parts to hay-wire up that circuitry for evaluation.
::::
::::I tend to question the way the cathode of the pentode is wired / treated in that shown application.
::::
::::The only other thing that comes to mind now is possibly your taking another ~10 K resistor and shunting that B+ filter resistor to get the
::::available B+ supplied to the plate circuitry up a bit to see if either it ups the very weak RF activity present now or if it is enough to
::::activate stronger oscillation.
::::
::::
::::Yet another re-draft of the RF and the Power supply areas, such as I would typically make them up..also with tube pin to functions referencing:
::::
::::http://img49.imageshack.us/img49/1423/little007redraftschemajpe5.jpg
::::J-pegged...soooo mag it up to size...
::::
::::73's de Edd

5/4/2007 11:58:09 AMTex
I really messed up on that one, it should have said tube pin #2 is now 4.8Vdc. With the extra 10k in the circuit pin #1 is 165Vdc. Pin #3 is 160Vdc. Without the extra 10k, #1 is 164dc, #3 is 154.8dc.I'm using a Craftsman digital multimeter. I switched to an old analog meter & pin #1 looks to be about 170, #3 about 165 with the extra 10k in circuit.. The tube does light up. With the extra 10k in the circuit & with the pot turned counterclockwise all the way pin #1 is 164.3dc, #3 is 158.9dc.

:You are definitely correct there, just wanted to positively confirm....plus my being blind....that voltage on the plate which was listed as 153 VDC should have went up , yet you give 4.8 Vdc as being its present reading ?
:To clear that up, hows about lifting one test lead to revert the circuit to its initial state and meter both the raw B+ at pin 1 and the plate voltage at pin 3 to reconfirm that they are at their initial values of ~161 Vdc at pin 1 and ~153Dvc at pin 3. If those initial voltage readings are not replicated, confirnm that you are establishing a good ground connection with the meterings negative probe...or not accidentally being in the meters AC mode. BTW..FIO..what meter are we using, DVM,VTVM,FET-VM, TVOM..or certainly..or hopefully
:not a common VOM.....(merely, in respect to capability of taking effectual 1st grid readings.)
:(Disregard further filament readings on pins 2 and 7, as they are of no concern..the filament is lighting up...right).
:Next, hows about reinstating the one loose clip lead to get the R3 "cluster" back so that you can confirm a reading again, if it is still at that low value, run the modulation control back max CCW / to minumum and then re confirm the plate reading to see if there is a variance to that plates voltage reading.
:Those are the only things that come to mind at the present , in a logical accounting for the drastic variance of the readings.
:
:73's de Edd
:
::I took a wire that has an alligator clip on each end I attached one alligator clip to one end of the original 10k, the other alligator clip attached to one end of another 10k. I took another wire that has an alligator clip on each end and attached it to the other end of the original 10k with the other alligator clip attached to the other end of the new 10k. The two 10k resistors are side by side not end to end. I beleive they are parallel not in series.
::
::hooooaaaa there, now ...the key words possibly being "along side the other one" and with the accompanying voltage readings given as now being
:::present on pin 3 would tend to infer that the originating DC voltage received from pin 1 is going through the original R3 (10K) and then into the
:::new 10K and then to over to the original R3's juncture at C4. Thus, a series connection of the resistorswas made. That would be giving less voltage
:::available to the plate circuitry than was previously supplied to it. Which your voltage is now reading.However, that is MUCH lower than I typically
:::would have expected.
:::The desired connection is a parallel connection, where the new 10K shunts across the original R3 and the load is shared between the side by side
:::parts such that the combined pairs resistance is then 5k and a bit heftier voltage drive is sent to the plate circuitry, the B+ enters the side by
:::side left sets of leads of the resistive pair and then exits over to the like tandem and the voltage then is at C4 electrolytic and on over as the
:::plate supply...hopefully to get the desired result.
:::Confirm the desired hook up now,
:::
:::73's de Edd
:::
::::I added another 10k resistor along side the other one, the voltage on tube pin #3 is now only 4.8dc, #5 is -.4dc,#7 is 5.5dc, the others seemed to stay about the same. The coil is the Miller RF-72, it isn't in a case. I have a picture of the coil & of the data sheet that came with the coil at: http://new.photos.yahoo.com/jrhradios
::::
:::::
:::::"AWRIGHT", already..so we're not quite ready to nominate you for the Bronze star for bravery...but....what the hey ..LOL
:::::
:::::Meaning....OK on the "no mini-micro RF burn" situation, and after looking at the schema and that B+ filter / dropping resistor value of a high 10 K I can see only a RF power capability of the unit in the order of one tenth watt being attainable thru the power supply, the way that 10 K resistor chokes it down, so that would not be enough to get that probable level of effective created RF.
:::::
:::::Plus after reviewing planigans data, which I just remembered him including in yet a separate tread of this common topic.
:::::Ref new comparisons:
:::::
:::::http://img455.imageshack.us/img455/9207/liltextroubleshootingvodc6.jpg
:::::
:::::YOU are having quite a high developed raw B+ in comparison to his voltage ...your ~161 Vdc versus his ~84 Vdc...which I normally
:::::would expect the higher voltage level that you are developing to be that voltage one expects to be seen by rectification by a solid
:::::state rectifier device, and his lower 84 volts to be that derived from a somewhat weakened rectifier tube.
:::::In either case BOTH of your units seem to now be loading down the power supply......pulling current.... such that the produced voltage drop is in the order of -5% for your unit while being -9% for p's.
:::::
:::::Its certainly not written in stone that one has to use the EXACT ***total parts package when building up that circuit but its variance can skew the enacting of like voltage comparisons between units.
:::::*** That's the fun of utilizing what you have on hand if they can be compatible.
:::::
:::::Also I still am still wondering about the source of supply of that RF coil that you are using. If it is in a large cased shield housing, it reminds me of some old units used in RF circuitry of WW1 tank receivers...basically meaning..... that I am unsure of its actual inductive values and intended design frequency of use. Also since you mentioned access to the coils, as you apparently have exposed
:::::them for viewing, any chance of that unit having any internal fixed capacitors shunting those windings?
:::::
:::::Finally , I am almost ready to include in this weekends activities, the pulling out a 6V6 , a tube socket, and two lab power supplies and the few parts to hay-wire up that circuitry for evaluation.
:::::
:::::I tend to question the way the cathode of the pentode is wired / treated in that shown application.
:::::
:::::The only other thing that comes to mind now is possibly your taking another ~10 K resistor and shunting that B+ filter resistor to get the
:::::available B+ supplied to the plate circuitry up a bit to see if either it ups the very weak RF activity present now or if it is enough to
:::::activate stronger oscillation.
:::::
:::::
:::::Yet another re-draft of the RF and the Power supply areas, such as I would typically make them up..also with tube pin to functions referencing:
:::::
:::::http://img49.imageshack.us/img49/1423/little007redraftschemajpe5.jpg
:::::J-pegged...soooo mag it up to size...
:::::
:::::73's de Edd

5/4/2007 12:34:47 PMEdd
Ah Haaa.. so that was the source of the error, eh...Just confirming your metering, as the unit to use on the metering of the 1st grid voltage would be the Craftsman with its High Z input and a corresponding minimal loading of that circuit...(any pulling down of that voltage level and producing a metering error).

Another thing unknown is the type of receiver being used for the monitoring. In my case I would want a continuous analog dial tuning that can be rather rapidly tuned across the BC band....as compared to ...say... a digital receiver that has to be gradually stepped / or / scanned across the spectrum in its arduous 10 Khz increments. Even a hand held pocket radio sized receiver being used for monitoring, would be better than that digital unit in trying to find the xmitters outputted signal.
The last factor would be having the monitoring receiver close...almost within a foot of the osc coil / or/ antenna until the outputted RF signal is initially zeroed in on.
Also, since that was a data referencing error on that voltage reading, you can return the modulation control back to ite prior position so that modulation will be present for an ease in identifying your signal..if now present.


73's de Edd

5/4/2007 5:04:21 PMTex
I'm using a small table model transistor radio & a 1950 tube radio both as monitors. I'm using a transistor radio with earplug socket for input. I have a wire that is 1/8" on one end & RCA on the other. I've checked for continuity between the connection inside the input radio & the wire that goes from the RCA plug to the pot. There is continuity.

:Ah Haaa.. so that was the source of the error, eh...Just confirming your metering, as the unit to use on the metering of the 1st grid voltage would be the Craftsman with its High Z input and a corresponding minimal loading of that circuit...(any pulling down of that voltage level and producing a metering error).
:
:Another thing unknown is the type of receiver being used for the monitoring. In my case I would want a continuous analog dial tuning that can be rather rapidly tuned across the BC band....as compared to ...say... a digital receiver that has to be gradually stepped / or / scanned across the spectrum in its arduous 10 Khz increments. Even a hand held pocket radio sized receiver being used for monitoring, would be better than that digital unit in trying to find the xmitters outputted signal.
:The last factor would be having the monitoring receiver close...almost within a foot of the osc coil / or/ antenna until the outputted RF signal is initially zeroed in on.
:Also, since that was a data referencing error on that voltage reading, you can return the modulation control back to ite prior position so that modulation will be present for an ease in identifying your signal..if now present.
:
:
:73's de Edd

5/4/2007 8:05:29 PMThomas Dermody
The potentiometer should have no affect on the operation of the transmitter. That said, you do not have to worry about where it is set.

The voltages are high because the unit is most likely not oscillating. I'd expect voltages no higher than about 130 with it oscillating, and probably more like 120, or even 80 or 90.

In all of these posts I still don't see evidence of you swapping the primary and secondary coils for eachother....just swapping the leads of one or the other. Please try that. All of your other wiring is just fine. No need to parallel resistors. The voltages are high enough.

Thomas

5/4/2007 9:11:32 PMPeter G Balazsy
I have nothing technical to offer here except my sincere appreciation observing the generous patience (commensurate with that of Job) as well as the persistence and perseverance demonstraded by the likes of messrs Edd, Thomas et al.
That's exactly what helps to make this particular forum invaluable.

5/4/2007 9:15:31 PMTex
I switched the wires, coil pin #1 now goes to the antenna & tube pin #3. Coil pin #2 goes to the + side of the electrolytics. Coil pin #3 goes to gnd. Coil pin #4 goes to the 150pf & 689pf. The meter readings are tube pin #1 161dc, #2 8.1dc, #3 152dc, #4 -.5dc, #5 -.5dc, #6 124ac, #7 7.3dc, #8 0v.

:The potentiometer should have no affect on the operation of the transmitter. That said, you do not have to worry about where it is set.
:
:The voltages are high because the unit is most likely not oscillating. I'd expect voltages no higher than about 130 with it oscillating, and probably more like 120, or even 80 or 90.
:
:In all of these posts I still don't see evidence of you swapping the primary and secondary coils for eachother....just swapping the leads of one or the other. Please try that. All of your other wiring is just fine. No need to parallel resistors. The voltages are high enough.
:
:Thomas

5/4/2007 11:39:43 PMThomas Dermody
Now try it out and see if you can receive anything. Place it right next to your radio.

Make sure you are using the slug of the coil to tune it. Make sure you are using a plastic alignment tool (available at Radio Shack). Don't use metal. If you can't find the signal by tuning over your radio's dial, tune to a quiet spot on your radio, first at the low end of the band, then in the middle, and then at the top end (not all the way at the end, but somewhere in the middle of the top and somewhere in the middle of the bottom, and somewhere in the middle of the center, all the time in a quiet place). When trying the transmitter in these three parts of the dial, turn the slug of the transmitter's oscillator coil all the way from top to bottom, and listen for transmission. Do this for each part of the band in a quiet spot.

If you don't get anything, reverse terminals 1 and 2. Repeat the above procedure.

Thomas

5/5/2007 11:25:16 AMTex
At Radio Shack the computer showed alignment tools to be in the store but they couldn't find them. I'm using a plastic knob screwed on the end of the brass bolt of the coil. I did the things you suggested but still no reception.

:Now try it out and see if you can receive anything. Place it right next to your radio.
:
:Make sure you are using the slug of the coil to tune it. Make sure you are using a plastic alignment tool (available at Radio Shack). Don't use metal. If you can't find the signal by tuning over your radio's dial, tune to a quiet spot on your radio, first at the low end of the band, then in the middle, and then at the top end (not all the way at the end, but somewhere in the middle of the top and somewhere in the middle of the bottom, and somewhere in the middle of the center, all the time in a quiet place). When trying the transmitter in these three parts of the dial, turn the slug of the transmitter's oscillator coil all the way from top to bottom, and listen for transmission. Do this for each part of the band in a quiet spot.
:
:If you don't get anything, reverse terminals 1 and 2. Repeat the above procedure.
:
:Thomas

5/5/2007 5:55:15 PMThomas Dermody
Hmmmmmmm......... Well, the plastic knob on the brass screw is a good idea.

Just remember that if you give up, you can send it my way. I'll pay for shipping if I don't get it running. That won't happen, though, so you can be sure that it will work.

One thing to remember is to be sure that your condenser values are correct. If you purchased brand new condensers, they can be coded instead of having actual values. For instance, 473K would be 47pf with 3 zeros afterward, making it 47000pf, or .047 MFD. The K is a tolerance code. If you were to put a 474K in place of a 473K, you'd have .47 MFD instead of .047. If you did a mix-up in a critical spot, such as the condensers on the coil, the unit wouldn't oscillate at proper frequency, or it wouldn't oscillate at all. Make sure that your condensers are the right ones.

Again, go over every bit of wiring, and make sure it is what it is supposed to be.

Incidently, what was the coil that you are using originally listed for?

T.

5/5/2007 7:15:46 PMRadiodoc
Thomas,

My thoughts are kind of like yours. I haven't been able to find any info on the Miller 72-RF coil. Might try an adjustable compression cap in place of the fixed cap across the coil say maybe 5 to 150 pf or something like that. However, like someone else in a previous post said, with a 12 volt winding on the transformer, I believe I would have used a 12 volt tube such as a 12V6 or a 12AQ5 instead of the 117 volt filament tube.

Radiodoc


:Hmmmmmmm......... Well, the plastic knob on the brass screw is a good idea.
:
:Just remember that if you give up, you can send it my way. I'll pay for shipping if I don't get it running. That won't happen, though, so you can be sure that it will work.
:
:One thing to remember is to be sure that your condenser values are correct. If you purchased brand new condensers, they can be coded instead of having actual values. For instance, 473K would be 47pf with 3 zeros afterward, making it 47000pf, or .047 MFD. The K is a tolerance code. If you were to put a 474K in place of a 473K, you'd have .47 MFD instead of .047. If you did a mix-up in a critical spot, such as the condensers on the coil, the unit wouldn't oscillate at proper frequency, or it wouldn't oscillate at all. Make sure that your condensers are the right ones.
:
:Again, go over every bit of wiring, and make sure it is what it is supposed to be.
:
:Incidently, what was the coil that you are using originally listed for?
:
:T.

5/6/2007 12:19:41 AMThomas Dermody
The 117 volt tube is just fine. It's on par to a 35L6 (which is like using a 6L6 or 12V6, etc.), and it even has its own rectifier, and, technically, doesn't need a power transformer, except for those who are shock-shy. I bought at 117N7 because it was cheaper, but the 117L7 is a fine tube. I've heard a lot about them, so I had to get one. I'd like to get some more. They're great for projects. A 70L7 is great for other .15 ampere tubes in series. I'm thinking about making a multi-line telephone signal for my work, because we need a light outside to let us know when the tele is rining, now that we're mandated to stand outside in good weather. There's talk about putting a phone outside, but I think that's a stupid idea for many reasons. Two 12AU7s will allow for 3 or 4 separate lines, and the 70L7 will activate the relay to turn on signal lights whenever the phone rings.

Anyway, back to the transmitter. Gotta get that bugger working!

T.

5/6/2007 1:05:37 AMLewis L.
:The 117 volt tube is just fine. It's on par to a 35L6 (which is like using a 6L6 or 12V6, etc.), and it even has its own rectifier, and, technically, doesn't need a power transformer, except for those who are shock-shy. I bought at 117N7 because it was cheaper, but the 117L7 is a fine tube. I've heard a lot about them, so I had to get one. I'd like to get some more. They're great for projects. A 70L7 is great for other .15 ampere tubes in series. I'm thinking about making a multi-line telephone signal for my work, because we need a light outside to let us know when the tele is rining, now that we're mandated to stand outside in good weather. There's talk about putting a phone outside, but I think that's a stupid idea for many reasons. Two 12AU7s will allow for 3 or 4 separate lines, and the 70L7 will activate the relay to turn on signal lights whenever the phone rings.
:
:Anyway, back to the transmitter. Gotta get that bugger working!
:
:T.

Hey, Thomas, an easier way to have multi line telephone ring notification is to bridge each line with a couple of, say, 27K resistors, then terminate the tip side of the resistors to one side of a NE-2, and the ring side resistors to the other side, then the NE-2 will light when any phone line rings, then have a CdS cell next to the bulb, in a light tight box, of course, and a relay in series with the CdS cell and a Voltage approiate to pull in the relay. Phone rings, neon bulb lights, CdS cell conducts, relay pulls in, and anything you want to happen after that happens.

Lewis

5/6/2007 1:30:16 AMThomas Dermody
True. That's a good idea. Never thought about resistors. I could use them to drive a 117L7, too. My problem was having condensers going to the different lines, and then having cross-talk, etc. With the low impedances of telephone lines, resistors probably won't cause cross-talk. I could use up to 1 meg resistors. The voltage of a telephone ring is super high. It could drive a relay all by itself, but that'd put an extra load on the line, and you'd need one relay per line. With 1 meg resistors on the super sensitive grid of a radio tube, everything will work fine.
T.
5/6/2007 1:39:56 AMLewis L.
:True. That's a good idea. Never thought about resistors. I could use them to drive a 117L7, too. My problem was having condensers going to the different lines, and then having cross-talk, etc. With the low impedances of telephone lines, resistors probably won't cause cross-talk. I could use up to 1 meg resistors. The voltage of a telephone ring is super high. It could drive a relay all by itself, but that'd put an extra load on the line, and you'd need one relay per line. With 1 meg resistors on the super sensitive grid of a radio tube, everything will work fine.
:T.
The standard ring Voltage iw 105V. at 20 Hz. It has been used since the first telephones ever rang, in fact the hand cranked magneto and the polarized ringer were invented by none other than Mr. Watson, of "Come here, Mr. Watson, I need you." fame, and has been used ever since. One side of the phone line, I forgot which, is connected to earth ground at the central office, so actually you could return one side of the ring detector to ground and save some resistors.
Lewis
5/6/2007 8:56:15 AMTex
I'm not ready to give up yet. The electrolytics are marked 22uf, the 68pf is marked 68+-5%, the 250 & 150 are marked the same way. The .01 is marked 103k, I checked another 103k, from the same supplier, using my yard sale cap tester & it registered just below .01. I"ll keep checking the wiring. The coil I'm using says "72 RF universal repl. BC band RF coil". It also has written in pencil "BC 382". Maybe a coil like the one at: http://antiqueradios.com/forum ... 541a01c78d , would work better.


:Hmmmmmmm......... Well, the plastic knob on the brass screw is a good idea.
:
:Just remember that if you give up, you can send it my way. I'll pay for shipping if I don't get it running. That won't happen, though, so you can be sure that it will work.
:
:One thing to remember is to be sure that your condenser values are correct. If you purchased brand new condensers, they can be coded instead of having actual values. For instance, 473K would be 47pf with 3 zeros afterward, making it 47000pf, or .047 MFD. The K is a tolerance code. If you were to put a 474K in place of a 473K, you'd have .47 MFD instead of .047. If you did a mix-up in a critical spot, such as the condensers on the coil, the unit wouldn't oscillate at proper frequency, or it wouldn't oscillate at all. Make sure that your condensers are the right ones.
:
:Again, go over every bit of wiring, and make sure it is what it is supposed to be.
:
:Incidently, what was the coil that you are using originally listed for?
:
:T.

5/6/2007 9:04:10 AMTex
:I'm not ready to give up yet. The electrolytics are marked 22uf, the 68pf is marked 68+-5%, the 250 & 150 are marked the same way. The .01 is marked 103k, I checked another 103k, from the same supplier, using my yard sale cap tester & it registered just below .01. I"ll keep checking the wiring. The coil I'm using says "72 RF universal repl. BC band RF coil". It also has written in pencil "BC 382". Maybe a coil like the one at: http://antiqueradios.com/forum ... 541a01c78d , would work better.
The link I posted didn't work for me so there is a photo of the coil (it's the one the tubbytwo built) at: http://new.photos.yahoo.com/jrhradios

:
:
::Hmmmmmmm......... Well, the plastic knob on the brass screw is a good idea.
::
::Just remember that if you give up, you can send it my way. I'll pay for shipping if I don't get it running. That won't happen, though, so you can be sure that it will work.
::
::One thing to remember is to be sure that your condenser values are correct. If you purchased brand new condensers, they can be coded instead of having actual values. For instance, 473K would be 47pf with 3 zeros afterward, making it 47000pf, or .047 MFD. The K is a tolerance code. If you were to put a 474K in place of a 473K, you'd have .47 MFD instead of .047. If you did a mix-up in a critical spot, such as the condensers on the coil, the unit wouldn't oscillate at proper frequency, or it wouldn't oscillate at all. Make sure that your condensers are the right ones.
::
::Again, go over every bit of wiring, and make sure it is what it is supposed to be.
::
::Incidently, what was the coil that you are using originally listed for?
::
::T.

5/6/2007 5:46:44 PMThomas Dermody
Well, if that is a universal replacement broadcast RF coil, then it is definitely made for tuning over the broadcast band. Also, the large winding of those coils is almost always the grid coil, and the small winding is almost always the plate coil, so if you have them wired as I said, then you should be in good shape. Again, if the thing won't oscillate, trying reversing terminals 1 and 2.

You can also try replacing the 120pF condenser with the large section of a tuning condenser from an old radio. See if it doesn't help. Adjust it over its range, and be sure that the frame side of the condenser is the side that's connected to B-.

Your voltages indicate that the unit isn't oscillating, though, so changing out the condenser probably won't help. Here's another thing to try if nothing else will work. Disconnect pin 5 from the potentiometer, and connect it to a 1 meg resistor and a .05 MFD condenser. Connect the other end of the .05 MFd condenser to B-. Connect the other end of the 1 meg resistor to B+. Now try the transmitter in the three parts of your radio dial. For each part, tune to a quiet spot and leave it there. Adjust the coil of the transmitter and see if you can hear it in the radio. Make sure that the large winding of your coil is in the grid circuit (where the 68pF condenser connects). It must be in that circuit. If you can't hear anything, reverse coil terminals 1 and 2. You can also connect your voltmeter to the side of the 10K resistor that DOES NOT connect to pin 1 (connect the positive meter lead there, and connect the negative lead to B-). Swap coil terminals 1 and 2 until you get the LOWEST voltage reading. If your oscillator starts oscillating, your voltage will go down.

If you manage to get the oscillator to work using the instructions given above, I'll have to come up with a different way of injecting audio. There are a few ways that will work well.

Print out the above and have it with you while you make changes. Read slowly and check off each step you make.

T.

5/7/2007 10:52:51 AMTex
I haven't tried it yet but I now have coil #1 to tube pin #3, to 250pf to ant. Coil #2 to the binding post where the 10k & the + side of one of the 22uf is attached. Coil #3 to the 68pf, to tube pin #4, to the 47k, to gnd. Coil #4 to gnd. I have a 1meg resistor & a .05 cap attached to tube pin #3. The 1meg to the binding post where the 10k, the + side of the 22uf, and the wire from coil #2 is attached. The .05 cap to gnd. Is that it?

:Well, if that is a universal replacement broadcast RF coil, then it is definitely made for tuning over the broadcast band. Also, the large winding of those coils is almost always the grid coil, and the small winding is almost always the plate coil, so if you have them wired as I said, then you should be in good shape. Again, if the thing won't oscillate, trying reversing terminals 1 and 2.
:
:You can also try replacing the 120pF condenser with the large section of a tuning condenser from an old radio. See if it doesn't help. Adjust it over its range, and be sure that the frame side of the condenser is the side that's connected to B-.
:
:Your voltages indicate that the unit isn't oscillating, though, so changing out the condenser probably won't help. Here's another thing to try if nothing else will work. Disconnect pin 5 from the potentiometer, and connect it to a 1 meg resistor and a .05 MFD condenser. Connect the other end of the .05 MFd condenser to B-. Connect the other end of the 1 meg resistor to B+. Now try the transmitter in the three parts of your radio dial. For each part, tune to a quiet spot and leave it there. Adjust the coil of the transmitter and see if you can hear it in the radio. Make sure that the large winding of your coil is in the grid circuit (where the 68pF condenser connects). It must be in that circuit. If you can't hear anything, reverse coil terminals 1 and 2. You can also connect your voltmeter to the side of the 10K resistor that DOES NOT connect to pin 1 (connect the positive meter lead there, and connect the negative lead to B-). Swap coil terminals 1 and 2 until you get the LOWEST voltage reading. If your oscillator starts oscillating, your voltage will go down.
:
:If you manage to get the oscillator to work using the instructions given above, I'll have to come up with a different way of injecting audio. There are a few ways that will work well.
:
:Print out the above and have it with you while you make changes. Read slowly and check off each step you make.
:
:T.

5/7/2007 1:09:14 PMThomas Dermody
Yep. That's it! Now try it out as I said. Tune the coil over its entire range while listening to quiet places on three parts of the dial. Also note the voltage on the coil side of the 10K resistor (you only have to do this once....not for each time you check the thing on your radio....just turn it on, take a voltage check, and then proceed with the above procedure).

If the unit won't oscillate, reverse coil terminals 1 and 2, but don't change the others.

If you can get the unit to transmit, connect pin 3 of the tube back to the volume control as was originally done. See if the unit still transmits. When you make this change, you may need to slightly re-tune the transmitter. If the transmitter will not work with pin 3 connected to the volume control, then I will have to come up with a different method for injecting audio. This might either be with a transformer in the plate circuit, or cathode injection.

When I have a bit of time, I'll build this transmitter for myself and see what I get.

T.

5/7/2007 2:48:17 PMTex
First a correction on my last post. I said I connected the resistor & cap to tube pin #3, I meant tube pin #5.
I tried it up & down the dial with the coil 1&2 in the first position then reversed but no reception. Also there was no change it the voltage 135Vdc from the coil side of the 10k to grnd when I switched the wires on the coil.

:Yep. That's it! Now try it out as I said. Tune the coil over its entire range while listening to quiet places on three parts of the dial. Also note the voltage on the coil side of the 10K resistor (you only have to do this once....not for each time you check the thing on your radio....just turn it on, take a voltage check, and then proceed with the above procedure).
:
:If the unit won't oscillate, reverse coil terminals 1 and 2, but don't change the others.
:
:If you can get the unit to transmit, connect pin 3 of the tube back to the volume control as was originally done. See if the unit still transmits. When you make this change, you may need to slightly re-tune the transmitter. If the transmitter will not work with pin 3 connected to the volume control, then I will have to come up with a different method for injecting audio. This might either be with a transformer in the plate circuit, or cathode injection.
:
:When I have a bit of time, I'll build this transmitter for myself and see what I get.
:
:T.

5/7/2007 3:56:39 PMThomas Dermody
Yeah. Pin 5 was the right one.

I'm going to bang my head against a wall for a while. Then, later, I'll build my own transmitter, which may work, but I still won't know why your's doesn't work. This is an interesting case. It may very well be the coil.

When you have the 1 Meg resistor connected from pin 5 to B+, and the .05 MFD condenser from pin 5 to B-, what voltage do you get at pin 5? Also, just for a last try, use a 10K resistor in place of the 1 Meg. resistor. With this resistor change, try the transmitter once again.

T.

T.

5/7/2007 5:11:40 PMTex
With the 1meg the voltage from pin #5 to common is 5Vdc on the analog meter & 6.1 on the digital. With the 10k the voltage is 34 on the analog & 34.3 on the digital. I tried it with each resistor in 3 places on the dial and adjusting the coil from top to bottom & then switched #1 & #2 on the coil & tried it with each resistor up & down the dial with no success.

:Yeah. Pin 5 was the right one.
:
:I'm going to bang my head against a wall for a while. Then, later, I'll build my own transmitter, which may work, but I still won't know why your's doesn't work. This is an interesting case. It may very well be the coil.
:
:When you have the 1 Meg resistor connected from pin 5 to B+, and the .05 MFD condenser from pin 5 to B-, what voltage do you get at pin 5? Also, just for a last try, use a 10K resistor in place of the 1 Meg. resistor. With this resistor change, try the transmitter once again.
:
:T.
:
:T.

5/8/2007 12:34:13 AMThomas Dermody
Ok. I'm going to build this transmitter myself and see what happens.

T.

5/8/2007 2:15:15 PMJeremy Korbe
:Ok. I'm going to build this transmitter myself and see what happens.
:
:T.

What about using a regular AM BCB coil out of a small AA5, and puting a cap across pins 1&2 for tunning? Might be something to try just to make sure it isn't the coil in there now.

Just an idea

Jeremy

5/8/2007 3:28:26 PMTex
::Ok. I'm going to build this transmitter myself and see what happens.
::
::T.
:
:What about using a regular AM BCB coil out of a small AA5, and puting a cap across pins 1&2 for tunning? Might be something to try just to make sure it isn't the coil in there now.
:
:Just an idea
:
:Jeremy \
I took the coil out of a GE C240. I don't know which pins are 1&2. The first pin (the one that goes to pin #5 of tube 12SA7) has no continuity to the other pins. The resistance between the second & third pins (moving clockwise) is 1.1ohms. The resistance between the second & fourth pins is 7.7ohms. The resistance between the third & fourth pins is 8.5ohms.
5/8/2007 4:29:54 PMEdd
OK..after having wired up that circuit and utilizing a familial 6AQ5 with the like values of aux components, with the sole exception of that specific " RF coil" used for the oscillator coil application..... of which, you seem to be the sole possessor.

Plus, with the additional alpha-numerical info that you supplied, I tend to lean even stronger in my belief that the transformer is from the WWII-thru-Korean vintage of tank command receiver. With some question of its added markings as per its being utilized within that specific BC-348 piece of equipment, which is a heterodyne frequency meter. Will have to see if I can find a schema for the latter.

The identical B+ level that you were using was being supplied with a lab power supply feeding the ciruitry.
Since I don't have your exact coil I opted to replicate the circuitry using a common IF transformer of the 50-60's vintage, the Automatic or K-tran type of 3/4 in alum case shielded unit. In that manner others can use the same technique in the evaluation of an inoperative or balky unit.
The hook up turns out to be using the same type of wiring connections that the unit uses in a common IF amp circuit.

For a visual technical reference consult:
http://img513.imageshack.us/img513/9581/455khzeyeeffxformerilluhz3.jpg

(With even the older, larger canned units depicted also.)

The transformer gets wired into the circuit with the same connections as depicted, and with the 3/4 size transformer the phasing for oscillation was correct as shown. Any chance that the unit doesn't osc, swap the ground and grid coupling capacitor connections to the transformer. After a hook up and taking a first grid reading with your specified meter in its DC mode...expect a negative voltage reading up in the multi volts...vice your previous .... ninus decimal 5 VDC ! Or possibly nothing again, if within that 50-50 % chance of the feed back phasing of ONE of the windings being in error.

With my test unit then oscillating , I clipped on and brought a test lead from the IF Transformers plate terminal over to the proximity of the monitor receivers loop antenna and the WHOLE AM RF spectrum of the receiver was swamped. Only "birdie" whistles at each stations frequencies, with only the strongest, letting the modulation peaks of audio creep through.

A check of the voltage across the 10k B+ filter / dropping resistor gave the figures to compute that the unit was consuming but a mere 1-5 mw when unmodulated. Not much at all, and a hint that this units initial prototype was evaluated using a healthier B+ voltage and then the unit scaled down in power by the value of that 10K series dropping resistor to keep the power level down to the prescribed RF output standards.
That’s all right, but, if cut down TOO low, it certainly makes for a balkier initial onset of oscillation from the circuit.

So, if you will try that , Tex, I believe that technique will initially verify the adequate emission capabilities/gain of your units TUBE, tolerable COMPONENT VALUES, along with a CORRECT INTERCONNECTING WIRING of the unit.

I was working my test set up with out modulation , after seeing that the meager peak-to-peak audio output capabilities being coupled in from an 1/8 inch miniature phone jack from a "dollar store" scanning FM receiver was thoroughly inadequate in level to audio modulate that screen grid.

Touching on the same topic, e.g. the tubes screen grid….. if by any chance that your initial evaluation still results in no oscillation, try this:

Lift the connection of any external wiring carrying modulation into the two terminals provided on the unit. Lift the end terminal of the modulation pot that normally was routed to ground. Now, that should have the pots outer connections completely free from any grounding connections and floating with only the pots center tap routed over to the tubes screen grid. Now it is your option as to which outer terminal you select, but the desired conditon is to have that pot at one extreme end of its rotation such that there will be 100k between that terminal and the center tap. . The idea now is to connect to that end terminal with one end of a clip/ jumper lead and clip its other lead to the lower level B+ past the 10k res. (Another option is to lift the grounding of the pot and take a loose 100K 1/2 w resistor and clip it from that B+ point over to the tubes screen grid at pin 5.)

The end result will be the biasing on the screen grid up to ~38 VDC and the adjunct upping of the oscillator output from that latter bucolic fractional watt level up to a 1/4 watt level.

Now, that should certainly shock the circuit into oscillation up to the point of completely SWAMPING out reception on the monitoring receiver. That one exception of the swap out of the grid-ground. or ..ground - grid phasing of one transformer winding should you have had no result at this time.

Should this not have resulted in oscillation up to this current sequence of tests, I think a recheck out of the parts/wiring would be in order since this circuit certainly works solidly with the use of a 455 KHZ IF transformer as the coil medium.

ASIDE:
Even at the higher output level, I now confirm that it is still not hefty enough to produce the neon lamp glow nor the mini RF skin burn….it seems that has to be on upwards into the 5W upwards levels of RF output.

FIO...if anyone happens to be test equipment shy...if they were to build this circuit up using an IF transformer, and then tune into their monitor receiver to a station operating on 910 Khz and then precisely trim in either the IF transformers slugs or trimmer capacitors to get a heterodyning Zero-beat. They would then have one PREE-CISELY on frequency signal generator for use in IF alignment at 455KHZ.
I consider the specified tube selection to be overkill in that application, instead, I would opt for the isolation provided by a like power transformer with either a 12 VAC filament supply and the use of a common 12BA6 for the tube. (Or 6BA6 with 6.5 ohm 2W series filament dropping resistor).
The main B+ being created from a solid state rectifier.

Its Tex time !

73's de Edd

5/8/2007 5:40:45 PMTex
We've gotten way above my intelligience level. Can I have step one in elementary terms?

:OK..after having wired up that circuit and utilizing a familial 6AQ5 with the like values of aux components, with the sole exception of that specific " RF coil" used for the oscillator coil application..... of which, you seem to be the sole possessor.
:
:Plus, with the additional alpha-numerical info that you supplied, I tend to lean even stronger in my belief that the transformer is from the WWII-thru-Korean vintage of tank command receiver. With some question of its added markings as per its being utilized within that specific BC-348 piece of equipment, which is a heterodyne frequency meter. Will have to see if I can find a schema for the latter.
:
:The identical B+ level that you were using was being supplied with a lab power supply feeding the ciruitry.
:Since I don't have your exact coil I opted to replicate the circuitry using a common IF transformer of the 50-60's vintage, the Automatic or K-tran type of 3/4 in alum case shielded unit. In that manner others can use the same technique in the evaluation of an inoperative or balky unit.
:The hook up turns out to be using the same type of wiring connections that the unit uses in a common IF amp circuit.
:
:For a visual technical reference consult:
:http://img513.imageshack.us/img513/9581/455khzeyeeffxformerilluhz3.jpg
:
:(With even the older, larger canned units depicted also.)
:
:The transformer gets wired into the circuit with the same connections as depicted, and with the 3/4 size transformer the phasing for oscillation was correct as shown. Any chance that the unit doesn't osc, swap the ground and grid coupling capacitor connections to the transformer. After a hook up and taking a first grid reading with your specified meter in its DC mode...expect a negative voltage reading up in the multi volts...vice your previous .... ninus decimal 5 VDC ! Or possibly nothing again, if within that 50-50 % chance of the feed back phasing of ONE of the windings being in error.
:
:With my test unit then oscillating , I clipped on and brought a test lead from the IF Transformers plate terminal over to the proximity of the monitor receivers loop antenna and the WHOLE AM RF spectrum of the receiver was swamped. Only "birdie" whistles at each stations frequencies, with only the strongest, letting the modulation peaks of audio creep through.
:
:A check of the voltage across the 10k B+ filter / dropping resistor gave the figures to compute that the unit was consuming but a mere 1-5 mw when unmodulated. Not much at all, and a hint that this units initial prototype was evaluated using a healthier B+ voltage and then the unit scaled down in power by the value of that 10K series dropping resistor to keep the power level down to the prescribed RF output standards.
:That’s all right, but, if cut down TOO low, it certainly makes for a balkier initial onset of oscillation from the circuit.
:
:So, if you will try that , Tex, I believe that technique will initially verify the adequate emission capabilities/gain of your units TUBE, tolerable COMPONENT VALUES, along with a CORRECT INTERCONNECTING WIRING of the unit.
:
:I was working my test set up with out modulation , after seeing that the meager peak-to-peak audio output capabilities being coupled in from an 1/8 inch miniature phone jack from a "dollar store" scanning FM receiver was thoroughly inadequate in level to audio modulate that screen grid.
:
:Touching on the same topic, e.g. the tubes screen grid….. if by any chance that your initial evaluation still results in no oscillation, try this:
:
:Lift the connection of any external wiring carrying modulation into the two terminals provided on the unit. Lift the end terminal of the modulation pot that normally was routed to ground. Now, that should have the pots outer connections completely free from any grounding connections and floating with only the pots center tap routed over to the tubes screen grid. Now it is your option as to which outer terminal you select, but the desired conditon is to have that pot at one extreme end of its rotation such that there will be 100k between that terminal and the center tap. . The idea now is to connect to that end terminal with one end of a clip/ jumper lead and clip its other lead to the lower level B+ past the 10k res. (Another option is to lift the grounding of the pot and take a loose 100K 1/2 w resistor and clip it from that B+ point over to the tubes screen grid at pin 5.)
:
:The end result will be the biasing on the screen grid up to ~38 VDC and the adjunct upping of the oscillator output from that latter bucolic fractional watt level up to a 1/4 watt level.
:
:Now, that should certainly shock the circuit into oscillation up to the point of completely SWAMPING out reception on the monitoring receiver. That one exception of the swap out of the grid-ground. or ..ground - grid phasing of one transformer winding should you have had no result at this time.
:
:Should this not have resulted in oscillation up to this current sequence of tests, I think a recheck out of the parts/wiring would be in order since this circuit certainly works solidly with the use of a 455 KHZ IF transformer as the coil medium.
:
:ASIDE:
:Even at the higher output level, I now confirm that it is still not hefty enough to produce the neon lamp glow nor the mini RF skin burn….it seems that has to be on upwards into the 5W upwards levels of RF output.
:
:FIO...if anyone happens to be test equipment shy...if they were to build this circuit up using an IF transformer, and then tune into their monitor receiver to a station operating on 910 Khz and then precisely trim in either the IF transformers slugs or trimmer capacitors to get a heterodyning Zero-beat. They would then have one PREE-CISELY on frequency signal generator for use in IF alignment at 455KHZ.
:I consider the specified tube selection to be overkill in that application, instead, I would opt for the isolation provided by a like power transformer with either a 12 VAC filament supply and the use of a common 12BA6 for the tube. (Or 6BA6 with 6.5 ohm 2W series filament dropping resistor).
:The main B+ being created from a solid state rectifier.
:
:Its Tex time !
:
:73's de Edd
:

5/8/2007 5:56:18 PMNorm Leal
Hi

Just about any coil will work if there is positive feedback. An IF transformer will also but gives a signal below the broadcast band unless wire is removed.

Problem with a circuit like this is FMing. When the transmitter is modulated it will cause frequency shift and distortion. Not bad if modulation is kept low, less than 10%?

Look over the following especially where it mentions 6888 tube. Go back a couple months in posts. This transmitter doesn't have a FM distortion problem.

http://antiqueradios.com/forums/viewforum.php?f=12

Norm

:We've gotten way above my intelligience level. Can I have step one in elementary terms?
:
::OK..after having wired up that circuit and utilizing a familial 6AQ5 with the like values of aux components, with the sole exception of that specific " RF coil" used for the oscillator coil application..... of which, you seem to be the sole possessor.
::
::Plus, with the additional alpha-numerical info that you supplied, I tend to lean even stronger in my belief that the transformer is from the WWII-thru-Korean vintage of tank command receiver. With some question of its added markings as per its being utilized within that specific BC-348 piece of equipment, which is a heterodyne frequency meter. Will have to see if I can find a schema for the latter.
::
::The identical B+ level that you were using was being supplied with a lab power supply feeding the ciruitry.
::Since I don't have your exact coil I opted to replicate the circuitry using a common IF transformer of the 50-60's vintage, the Automatic or K-tran type of 3/4 in alum case shielded unit. In that manner others can use the same technique in the evaluation of an inoperative or balky unit.
::The hook up turns out to be using the same type of wiring connections that the unit uses in a common IF amp circuit.
::
::For a visual technical reference consult:
::http://img513.imageshack.us/img513/9581/455khzeyeeffxformerilluhz3.jpg
::
::(With even the older, larger canned units depicted also.)
::
::The transformer gets wired into the circuit with the same connections as depicted, and with the 3/4 size transformer the phasing for oscillation was correct as shown. Any chance that the unit doesn't osc, swap the ground and grid coupling capacitor connections to the transformer. After a hook up and taking a first grid reading with your specified meter in its DC mode...expect a negative voltage reading up in the multi volts...vice your previous .... ninus decimal 5 VDC ! Or possibly nothing again, if within that 50-50 % chance of the feed back phasing of ONE of the windings being in error.
::
::With my test unit then oscillating , I clipped on and brought a test lead from the IF Transformers plate terminal over to the proximity of the monitor receivers loop antenna and the WHOLE AM RF spectrum of the receiver was swamped. Only "birdie" whistles at each stations frequencies, with only the strongest, letting the modulation peaks of audio creep through.
::
::A check of the voltage across the 10k B+ filter / dropping resistor gave the figures to compute that the unit was consuming but a mere 1-5 mw when unmodulated. Not much at all, and a hint that this units initial prototype was evaluated using a healthier B+ voltage and then the unit scaled down in power by the value of that 10K series dropping resistor to keep the power level down to the prescribed RF output standards.
::That’s all right, but, if cut down TOO low, it certainly makes for a balkier initial onset of oscillation from the circuit.
::
::So, if you will try that , Tex, I believe that technique will initially verify the adequate emission capabilities/gain of your units TUBE, tolerable COMPONENT VALUES, along with a CORRECT INTERCONNECTING WIRING of the unit.
::
::I was working my test set up with out modulation , after seeing that the meager peak-to-peak audio output capabilities being coupled in from an 1/8 inch miniature phone jack from a "dollar store" scanning FM receiver was thoroughly inadequate in level to audio modulate that screen grid.
::
::Touching on the same topic, e.g. the tubes screen grid….. if by any chance that your initial evaluation still results in no oscillation, try this:
::
::Lift the connection of any external wiring carrying modulation into the two terminals provided on the unit. Lift the end terminal of the modulation pot that normally was routed to ground. Now, that should have the pots outer connections completely free from any grounding connections and floating with only the pots center tap routed over to the tubes screen grid. Now it is your option as to which outer terminal you select, but the desired conditon is to have that pot at one extreme end of its rotation such that there will be 100k between that terminal and the center tap. . The idea now is to connect to that end terminal with one end of a clip/ jumper lead and clip its other lead to the lower level B+ past the 10k res. (Another option is to lift the grounding of the pot and take a loose 100K 1/2 w resistor and clip it from that B+ point over to the tubes screen grid at pin 5.)
::
::The end result will be the biasing on the screen grid up to ~38 VDC and the adjunct upping of the oscillator output from that latter bucolic fractional watt level up to a 1/4 watt level.
::
::Now, that should certainly shock the circuit into oscillation up to the point of completely SWAMPING out reception on the monitoring receiver. That one exception of the swap out of the grid-ground. or ..ground - grid phasing of one transformer winding should you have had no result at this time.
::
::Should this not have resulted in oscillation up to this current sequence of tests, I think a recheck out of the parts/wiring would be in order since this circuit certainly works solidly with the use of a 455 KHZ IF transformer as the coil medium.
::
::ASIDE:
::Even at the higher output level, I now confirm that it is still not hefty enough to produce the neon lamp glow nor the mini RF skin burn….it seems that has to be on upwards into the 5W upwards levels of RF output.
::
::FIO...if anyone happens to be test equipment shy...if they were to build this circuit up using an IF transformer, and then tune into their monitor receiver to a station operating on 910 Khz and then precisely trim in either the IF transformers slugs or trimmer capacitors to get a heterodyning Zero-beat. They would then have one PREE-CISELY on frequency signal generator for use in IF alignment at 455KHZ.
::I consider the specified tube selection to be overkill in that application, instead, I would opt for the isolation provided by a like power transformer with either a 12 VAC filament supply and the use of a common 12BA6 for the tube. (Or 6BA6 with 6.5 ohm 2W series filament dropping resistor).
::The main B+ being created from a solid state rectifier.
::
::Its Tex time !
::
::73's de Edd
::

5/8/2007 6:07:59 PMJeremy Korbe
http://antiqueradios.com/forums/viewtopic.php?t=63310

This is the orginal thread, read the post with 6888 in the headings, the are very helpful. He did a very good job of disgining this. You should have almost everything to build it, except for the clock oscilator probly, i built it, and it works great. However frequency can only be changed with changing the crystal used. I was thinking of using a 555 as a VFO, but don't have alot of time to expirament. What do you think?

Jeremy

5/8/2007 11:07:35 PMNorm Leal
Hi Jeremy

We discussed the 555 on the other forum. Don't think it will oscillate at broadcast band frequencies. Data book only shows timing components to 100KHz.

You could build an oscillator to feed grid #1 of the 6888. The original circuit was simple, something almost anyone could follow.

Don't use the output tube as an oscillator. Modulation will cause a shift in frequency. This in turn causes FM and distortion.

Norm

:http://antiqueradios.com/forums/viewtopic.php?t=63310
:
:This is the orginal thread, read the post with 6888 in the headings, the are very helpful. He did a very good job of disgining this. You should have almost everything to build it, except for the clock oscilator probly, i built it, and it works great. However frequency can only be changed with changing the crystal used. I was thinking of using a 555 as a VFO, but don't have alot of time to expirament. What do you think?
:
:Jeremy

5/8/2007 11:26:11 PMJeremy Korbe
Ya, Norm, i'm gonna take your advice, and build an osc. using the pentode section of a 6U8A as the osc. and the triode as an audio amp. Sorry tex, i Don't mean to but in.

Jeremy

:Hi Jeremy
:
: We discussed the 555 on the other forum. Don't think it will oscillate at broadcast band frequencies. Data book only shows timing components to 100KHz.
:
: You could build an oscillator to feed grid #1 of the 6888. The original circuit was simple, something almost anyone could follow.
:
: Don't use the output tube as an oscillator. Modulation will cause a shift in frequency. This in turn causes FM and distortion.
:
:Norm
:
::http://antiqueradios.com/forums/viewtopic.php?t=63310
::
::This is the orginal thread, read the post with 6888 in the headings, the are very helpful. He did a very good job of disgining this. You should have almost everything to build it, except for the clock oscilator probly, i built it, and it works great. However frequency can only be changed with changing the crystal used. I was thinking of using a 555 as a VFO, but don't have alot of time to expirament. What do you think?
::
::Jeremy

5/8/2007 7:39:03 PMEdd
:We've gotten way above my intelligience level. Can I have step one in elementary terms?

----------------------------------------------------------------------------------------------------------------------------------------

Step one:
Substitute in a 455 kC IF transformer for your coil...as I suspect that it is the "problem".

If that then works , all potential trouble aspects should typically be eliminated.
There is only the 50% error probability of it not initially working due to phasing of the feed back signal so the 1'st grid to ground wires need to be transposed...but..I believe that you have that action down to a fine art now.....LOL.

BTW ...I couldn't rapidly read all the forks of this lengthly thread and locate that military designator
number that you found written on its box or on the unit itself...what was that number again, as I see that I gave the wrong numbering above for the freq meter above.

73's de Edd

----------------------------------------------------------------------------------------------------------------------------------------

:
::OK..after having wired up that circuit and utilizing a familial 6AQ5 with the like values of aux components, with the sole exception of that specific " RF coil" used for the oscillator coil application..... of which, you seem to be the sole possessor.
::
::Plus, with the additional alpha-numerical info that you supplied, I tend to lean even stronger in my belief that the transformer is from the WWII-thru-Korean vintage of tank command receiver. With some question of its added markings as per its being utilized within that specific BC-348 piece of equipment, which is a heterodyne frequency meter. Will have to see if I can find a schema for the latter.
::
::The identical B+ level that you were using was being supplied with a lab power supply feeding the ciruitry.
::Since I don't have your exact coil I opted to replicate the circuitry using a common IF transformer of the 50-60's vintage, the Automatic or K-tran type of 3/4 in alum case shielded unit. In that manner others can use the same technique in the evaluation of an inoperative or balky unit.
::The hook up turns out to be using the same type of wiring connections that the unit uses in a common IF amp circuit.
::
::For a visual technical reference consult:
::http://img513.imageshack.us/img513/9581/455khzeyeeffxformerilluhz3.jpg
::
::(With even the older, larger canned units depicted also.)
::
::The transformer gets wired into the circuit with the same connections as depicted, and with the 3/4 size transformer the phasing for oscillation was correct as shown. Any chance that the unit doesn't osc, swap the ground and grid coupling capacitor connections to the transformer. After a hook up and taking a first grid reading with your specified meter in its DC mode...expect a negative voltage reading up in the multi volts...vice your previous .... ninus decimal 5 VDC ! Or possibly nothing again, if within that 50-50 % chance of the feed back phasing of ONE of the windings being in error.
::
::With my test unit then oscillating , I clipped on and brought a test lead from the IF Transformers plate terminal over to the proximity of the monitor receivers loop antenna and the WHOLE AM RF spectrum of the receiver was swamped. Only "birdie" whistles at each stations frequencies, with only the strongest, letting the modulation peaks of audio creep through.
::
::A check of the voltage across the 10k B+ filter / dropping resistor gave the figures to compute that the unit was consuming but a mere 1-5 mw when unmodulated. Not much at all, and a hint that this units initial prototype was evaluated using a healthier B+ voltage and then the unit scaled down in power by the value of that 10K series dropping resistor to keep the power level down to the prescribed RF output standards.
::That’s all right, but, if cut down TOO low, it certainly makes for a balkier initial onset of oscillation from the circuit.
::
::So, if you will try that , Tex, I believe that technique will initially verify the adequate emission capabilities/gain of your units TUBE, tolerable COMPONENT VALUES, along with a CORRECT INTERCONNECTING WIRING of the unit.
::
::I was working my test set up with out modulation , after seeing that the meager peak-to-peak audio output capabilities being coupled in from an 1/8 inch miniature phone jack from a "dollar store" scanning FM receiver was thoroughly inadequate in level to audio modulate that screen grid.
::
::Touching on the same topic, e.g. the tubes screen grid….. if by any chance that your initial evaluation still results in no oscillation, try this:
::
::Lift the connection of any external wiring carrying modulation into the two terminals provided on the unit. Lift the end terminal of the modulation pot that normally was routed to ground. Now, that should have the pots outer connections completely free from any grounding connections and floating with only the pots center tap routed over to the tubes screen grid. Now it is your option as to which outer terminal you select, but the desired conditon is to have that pot at one extreme end of its rotation such that there will be 100k between that terminal and the center tap. . The idea now is to connect to that end terminal with one end of a clip/ jumper lead and clip its other lead to the lower level B+ past the 10k res. (Another option is to lift the grounding of the pot and take a loose 100K 1/2 w resistor and clip it from that B+ point over to the tubes screen grid at pin 5.)
::
::The end result will be the biasing on the screen grid up to ~38 VDC and the adjunct upping of the oscillator output from that latter bucolic fractional watt level up to a 1/4 watt level.
::
::Now, that should certainly shock the circuit into oscillation up to the point of completely SWAMPING out reception on the monitoring receiver. That one exception of the swap out of the grid-ground. or ..ground - grid phasing of one transformer winding should you have had no result at this time.
::
::Should this not have resulted in oscillation up to this current sequence of tests, I think a recheck out of the parts/wiring would be in order since this circuit certainly works solidly with the use of a 455 KHZ IF transformer as the coil medium.
::
::ASIDE:
::Even at the higher output level, I now confirm that it is still not hefty enough to produce the neon lamp glow nor the mini RF skin burn….it seems that has to be on upwards into the 5W upwards levels of RF output.
::
::FIO...if anyone happens to be test equipment shy...if they were to build this circuit up using an IF transformer, and then tune into their monitor receiver to a station operating on 910 Khz and then precisely trim in either the IF transformers slugs or trimmer capacitors to get a heterodyning Zero-beat. They would then have one PREE-CISELY on frequency signal generator for use in IF alignment at 455KHZ.
::I consider the specified tube selection to be overkill in that application, instead, I would opt for the isolation provided by a like power transformer with either a 12 VAC filament supply and the use of a common 12BA6 for the tube. (Or 6BA6 with 6.5 ohm 2W series filament dropping resistor).
::The main B+ being created from a solid state rectifier.
::
::Its Tex time !
::
::73's de Edd
::

5/8/2007 8:02:53 PMTex
The box says "CAT No. 72RF, Univesal Repl.,BC band RF coil". Someone has written in pencil "BC 382".

::We've gotten way above my intelligience level. Can I have step one in elementary terms?
:
:----------------------------------------------------------------------------------------------------------------------------------------
:
:Step one:
:Substitute in a 455 kC IF transformer for your coil...as I suspect that it is the "problem".
:
:If that then works , all potential trouble aspects should typically be eliminated.
:There is only the 50% error probability of it not initially working due to phasing of the feed back signal so the 1'st grid to ground wires need to be transposed...but..I believe that you have that action down to a fine art now.....LOL.
:
:BTW ...I couldn't rapidly read all the forks of this lengthly thread and locate that military designator
:number that you found written on its box or on the unit itself...what was that number again, as I see that I gave the wrong numbering above for the freq meter above.
:
:73's de Edd
:
:----------------------------------------------------------------------------------------------------------------------------------------
:
:
:
::
:::OK..after having wired up that circuit and utilizing a familial 6AQ5 with the like values of aux components, with the sole exception of that specific " RF coil" used for the oscillator coil application..... of which, you seem to be the sole possessor.
:::
:::Plus, with the additional alpha-numerical info that you supplied, I tend to lean even stronger in my belief that the transformer is from the WWII-thru-Korean vintage of tank command receiver. With some question of its added markings as per its being utilized within that specific BC-348 piece of equipment, which is a heterodyne frequency meter. Will have to see if I can find a schema for the latter.
:::
:::The identical B+ level that you were using was being supplied with a lab power supply feeding the ciruitry.
:::Since I don't have your exact coil I opted to replicate the circuitry using a common IF transformer of the 50-60's vintage, the Automatic or K-tran type of 3/4 in alum case shielded unit. In that manner others can use the same technique in the evaluation of an inoperative or balky unit.
:::The hook up turns out to be using the same type of wiring connections that the unit uses in a common IF amp circuit.
:::
:::For a visual technical reference consult:
:::http://img513.imageshack.us/img513/9581/455khzeyeeffxformerilluhz3.jpg
:::
:::(With even the older, larger canned units depicted also.)
:::
:::The transformer gets wired into the circuit with the same connections as depicted, and with the 3/4 size transformer the phasing for oscillation was correct as shown. Any chance that the unit doesn't osc, swap the ground and grid coupling capacitor connections to the transformer. After a hook up and taking a first grid reading with your specified meter in its DC mode...expect a negative voltage reading up in the multi volts...vice your previous .... ninus decimal 5 VDC ! Or possibly nothing again, if within that 50-50 % chance of the feed back phasing of ONE of the windings being in error.
:::
:::With my test unit then oscillating , I clipped on and brought a test lead from the IF Transformers plate terminal over to the proximity of the monitor receivers loop antenna and the WHOLE AM RF spectrum of the receiver was swamped. Only "birdie" whistles at each stations frequencies, with only the strongest, letting the modulation peaks of audio creep through.
:::
:::A check of the voltage across the 10k B+ filter / dropping resistor gave the figures to compute that the unit was consuming but a mere 1-5 mw when unmodulated. Not much at all, and a hint that this units initial prototype was evaluated using a healthier B+ voltage and then the unit scaled down in power by the value of that 10K series dropping resistor to keep the power level down to the prescribed RF output standards.
:::That’s all right, but, if cut down TOO low, it certainly makes for a balkier initial onset of oscillation from the circuit.
:::
:::So, if you will try that , Tex, I believe that technique will initially verify the adequate emission capabilities/gain of your units TUBE, tolerable COMPONENT VALUES, along with a CORRECT INTERCONNECTING WIRING of the unit.
:::
:::I was working my test set up with out modulation , after seeing that the meager peak-to-peak audio output capabilities being coupled in from an 1/8 inch miniature phone jack from a "dollar store" scanning FM receiver was thoroughly inadequate in level to audio modulate that screen grid.
:::
:::Touching on the same topic, e.g. the tubes screen grid….. if by any chance that your initial evaluation still results in no oscillation, try this:
:::
:::Lift the connection of any external wiring carrying modulation into the two terminals provided on the unit. Lift the end terminal of the modulation pot that normally was routed to ground. Now, that should have the pots outer connections completely free from any grounding connections and floating with only the pots center tap routed over to the tubes screen grid. Now it is your option as to which outer terminal you select, but the desired conditon is to have that pot at one extreme end of its rotation such that there will be 100k between that terminal and the center tap. . The idea now is to connect to that end terminal with one end of a clip/ jumper lead and clip its other lead to the lower level B+ past the 10k res. (Another option is to lift the grounding of the pot and take a loose 100K 1/2 w resistor and clip it from that B+ point over to the tubes screen grid at pin 5.)
:::
:::The end result will be the biasing on the screen grid up to ~38 VDC and the adjunct upping of the oscillator output from that latter bucolic fractional watt level up to a 1/4 watt level.
:::
:::Now, that should certainly shock the circuit into oscillation up to the point of completely SWAMPING out reception on the monitoring receiver. That one exception of the swap out of the grid-ground. or ..ground - grid phasing of one transformer winding should you have had no result at this time.
:::
:::Should this not have resulted in oscillation up to this current sequence of tests, I think a recheck out of the parts/wiring would be in order since this circuit certainly works solidly with the use of a 455 KHZ IF transformer as the coil medium.
:::
:::ASIDE:
:::Even at the higher output level, I now confirm that it is still not hefty enough to produce the neon lamp glow nor the mini RF skin burn….it seems that has to be on upwards into the 5W upwards levels of RF output.
:::
:::FIO...if anyone happens to be test equipment shy...if they were to build this circuit up using an IF transformer, and then tune into their monitor receiver to a station operating on 910 Khz and then precisely trim in either the IF transformers slugs or trimmer capacitors to get a heterodyning Zero-beat. They would then have one PREE-CISELY on frequency signal generator for use in IF alignment at 455KHZ.
:::I consider the specified tube selection to be overkill in that application, instead, I would opt for the isolation provided by a like power transformer with either a 12 VAC filament supply and the use of a common 12BA6 for the tube. (Or 6BA6 with 6.5 ohm 2W series filament dropping resistor).
:::The main B+ being created from a solid state rectifier.
:::
:::Its Tex time !
:::
:::73's de Edd
:::

5/9/2007 12:25:39 PMTex
I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.

::We've gotten way above my intelligience level. Can I have step one in elementary terms?
:
:----------------------------------------------------------------------------------------------------------------------------------------
:
:Step one:
:Substitute in a 455 kC IF transformer for your coil...as I suspect that it is the "problem".
:
:If that then works , all potential trouble aspects should typically be eliminated.
:There is only the 50% error probability of it not initially working due to phasing of the feed back signal so the 1'st grid to ground wires need to be transposed...but..I believe that you have that action down to a fine art now.....LOL.
:
:BTW ...I couldn't rapidly read all the forks of this lengthly thread and locate that military designator
:number that you found written on its box or on the unit itself...what was that number again, as I see that I gave the wrong numbering above for the freq meter above.
:
:73's de Edd
:
:----------------------------------------------------------------------------------------------------------------------------------------
:
:
:
::
:::OK..after having wired up that circuit and utilizing a familial 6AQ5 with the like values of aux components, with the sole exception of that specific " RF coil" used for the oscillator coil application..... of which, you seem to be the sole possessor.
:::
:::Plus, with the additional alpha-numerical info that you supplied, I tend to lean even stronger in my belief that the transformer is from the WWII-thru-Korean vintage of tank command receiver. With some question of its added markings as per its being utilized within that specific BC-348 piece of equipment, which is a heterodyne frequency meter. Will have to see if I can find a schema for the latter.
:::
:::The identical B+ level that you were using was being supplied with a lab power supply feeding the ciruitry.
:::Since I don't have your exact coil I opted to replicate the circuitry using a common IF transformer of the 50-60's vintage, the Automatic or K-tran type of 3/4 in alum case shielded unit. In that manner others can use the same technique in the evaluation of an inoperative or balky unit.
:::The hook up turns out to be using the same type of wiring connections that the unit uses in a common IF amp circuit.
:::
:::For a visual technical reference consult:
:::http://img513.imageshack.us/img513/9581/455khzeyeeffxformerilluhz3.jpg
:::
:::(With even the older, larger canned units depicted also.)
:::
:::The transformer gets wired into the circuit with the same connections as depicted, and with the 3/4 size transformer the phasing for oscillation was correct as shown. Any chance that the unit doesn't osc, swap the ground and grid coupling capacitor connections to the transformer. After a hook up and taking a first grid reading with your specified meter in its DC mode...expect a negative voltage reading up in the multi volts...vice your previous .... ninus decimal 5 VDC ! Or possibly nothing again, if within that 50-50 % chance of the feed back phasing of ONE of the windings being in error.
:::
:::With my test unit then oscillating , I clipped on and brought a test lead from the IF Transformers plate terminal over to the proximity of the monitor receivers loop antenna and the WHOLE AM RF spectrum of the receiver was swamped. Only "birdie" whistles at each stations frequencies, with only the strongest, letting the modulation peaks of audio creep through.
:::
:::A check of the voltage across the 10k B+ filter / dropping resistor gave the figures to compute that the unit was consuming but a mere 1-5 mw when unmodulated. Not much at all, and a hint that this units initial prototype was evaluated using a healthier B+ voltage and then the unit scaled down in power by the value of that 10K series dropping resistor to keep the power level down to the prescribed RF output standards.
:::That’s all right, but, if cut down TOO low, it certainly makes for a balkier initial onset of oscillation from the circuit.
:::
:::So, if you will try that , Tex, I believe that technique will initially verify the adequate emission capabilities/gain of your units TUBE, tolerable COMPONENT VALUES, along with a CORRECT INTERCONNECTING WIRING of the unit.
:::
:::I was working my test set up with out modulation , after seeing that the meager peak-to-peak audio output capabilities being coupled in from an 1/8 inch miniature phone jack from a "dollar store" scanning FM receiver was thoroughly inadequate in level to audio modulate that screen grid.
:::
:::Touching on the same topic, e.g. the tubes screen grid….. if by any chance that your initial evaluation still results in no oscillation, try this:
:::
:::Lift the connection of any external wiring carrying modulation into the two terminals provided on the unit. Lift the end terminal of the modulation pot that normally was routed to ground. Now, that should have the pots outer connections completely free from any grounding connections and floating with only the pots center tap routed over to the tubes screen grid. Now it is your option as to which outer terminal you select, but the desired conditon is to have that pot at one extreme end of its rotation such that there will be 100k between that terminal and the center tap. . The idea now is to connect to that end terminal with one end of a clip/ jumper lead and clip its other lead to the lower level B+ past the 10k res. (Another option is to lift the grounding of the pot and take a loose 100K 1/2 w resistor and clip it from that B+ point over to the tubes screen grid at pin 5.)
:::
:::The end result will be the biasing on the screen grid up to ~38 VDC and the adjunct upping of the oscillator output from that latter bucolic fractional watt level up to a 1/4 watt level.
:::
:::Now, that should certainly shock the circuit into oscillation up to the point of completely SWAMPING out reception on the monitoring receiver. That one exception of the swap out of the grid-ground. or ..ground - grid phasing of one transformer winding should you have had no result at this time.
:::
:::Should this not have resulted in oscillation up to this current sequence of tests, I think a recheck out of the parts/wiring would be in order since this circuit certainly works solidly with the use of a 455 KHZ IF transformer as the coil medium.
:::
:::ASIDE:
:::Even at the higher output level, I now confirm that it is still not hefty enough to produce the neon lamp glow nor the mini RF skin burn….it seems that has to be on upwards into the 5W upwards levels of RF output.
:::
:::FIO...if anyone happens to be test equipment shy...if they were to build this circuit up using an IF transformer, and then tune into their monitor receiver to a station operating on 910 Khz and then precisely trim in either the IF transformers slugs or trimmer capacitors to get a heterodyning Zero-beat. They would then have one PREE-CISELY on frequency signal generator for use in IF alignment at 455KHZ.
:::I consider the specified tube selection to be overkill in that application, instead, I would opt for the isolation provided by a like power transformer with either a 12 VAC filament supply and the use of a common 12BA6 for the tube. (Or 6BA6 with 6.5 ohm 2W series filament dropping resistor).
:::The main B+ being created from a solid state rectifier.
:::
:::Its Tex time !
:::
:::73's de Edd
:::

5/8/2007 5:58:59 PMJeremy Korbe
:::Ok. I'm going to build this transmitter myself and see what happens.
:::
:::T.
::
::What about using a regular AM BCB coil out of a small AA5, and puting a cap across pins 1&2 for tunning? Might be something to try just to make sure it isn't the coil in there now.
::
::Just an idea
::
::Jeremy \
:I took the coil out of a GE C240. I don't know which pins are 1&2. The first pin (the one that goes to pin #5 of tube 12SA7) has no continuity to the other pins. The resistance between the second & third pins (moving clockwise) is 1.1ohms. The resistance between the second & fourth pins is 7.7ohms. The resistance between the third & fourth pins is 8.5ohms.

No continuity of the pin that goes to the #5 pin of the 12SA7 says that the coil is bad. Pin 5 is the 1st grid. There needs to be seperate windings.

5/8/2007 7:17:36 PMEdd
::::Ok. I'm going to build this transmitter myself and see what happens.
::::
::::T.
:::
:::What about using a regular AM BCB coil out of a small AA5, and puting a cap across pins 1&2 for tunning? Might be something to try just to make sure it isn't the coil in there now.
:::
:::Just an idea
:::
:::Jeremy \
::I took the coil out of a GE C240. I don't know which pins are 1&2. The first pin (the one that goes to pin #5 of tube 12SA7) has no continuity to the other pins. The resistance between the second & third pins (moving clockwise) is 1.1ohms. The resistance between the second & fourth pins is 7.7ohms. The resistance between the third & fourth pins is 8.5ohms.
:
:No continuity of the pin that goes to the #5 pin of the 12SA7 says that the coil is bad. Pin 5 is the 1st grid. There needs to be seperate windings.

Considering pin 5 of the 12SA7 being the first grid..and used in an oscillator circuit.

In several instances, coil maunfacturers will have a coil winding wire affixed to its wiring terminal on the units coil form and then route that wire along that form and then go atop the winding initiating several turns atop the winding, whereupon that form fitted winding action upon the coil proper is stopped with the end length of that wire left completely free and unterminated.
The idea being that it can then serve as the grid coupling "capacitor" feeding into that that osc circuit, by virtue of its proximity to, and the "gimmick" capacitive coupling effect it creates.

73's de Edd

5/8/2007 11:24:39 PMThomas Dermody
Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).

T.

5/9/2007 12:48:30 PMTex
I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.

:Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
:
:
:
:T.

5/9/2007 5:21:17 PMEdd

Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?

Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.

73's de Edd


:I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
:
::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
::
::
::
::T.

5/9/2007 8:30:17 PMTex
This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.

:
:Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
:you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
:coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
:Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
:I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
:at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
:Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
:
:Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
:
:
:73's de Edd
:
:
::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
::
:::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
:::
:::
:::
:::T.
5/10/2007 2:22:52 PMEdd

Step two:

Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.

Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.

Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.

Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.

Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.

you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
wanting to use this setup for a 455 KC alignment generator.

Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.

Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
why they were getting their quirky DVM meter readings while working with AC powered equipment.

Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.

AC line voltage...metering oddities....technical referencing:

http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg

73’s de Edd

-------------------------B/T------------------------


:This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
:
::
::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
::
::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
::
::
::73's de Edd
::
::
:::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
:::
::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
::::
::::
::::
::::T.

5/10/2007 6:20:21 PMTex
I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.

:
:
:Step two:
:
:Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
:
:Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
:
:Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
:Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
:
:Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
:As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
:
:Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
:If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
:BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
:
:you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
:wanting to use this setup for a 455 KC alignment generator.
:
:Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
:electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
:Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
:
:Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
:why they were getting their quirky DVM meter readings while working with AC powered equipment.
:
:Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
:
:AC line voltage...metering oddities....technical referencing:
:
:http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
:
:73’s de Edd
:
:-------------------------B/T------------------------
:
:
::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
::
:::
:::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
:::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
:::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
:::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
:::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
:::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
:::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
:::
:::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
:::
:::
:::73's de Edd
:::
:::
::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
::::
:::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
:::::
:::::
:::::
:::::T.

5/10/2007 7:00:27 PMEdd
Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.

73's de Edd

----------------------------------------------------------------------------------B/T-----------------------------------------------------

:I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
:
::
::
::Step two:
::
::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
::
::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
::
::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
::
::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
::
::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
::
::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
::wanting to use this setup for a 455 KC alignment generator.
::
::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
::
::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
::why they were getting their quirky DVM meter readings while working with AC powered equipment.
::
::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
::
::AC line voltage...metering oddities....technical referencing:
::
::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
::
::73’s de Edd
::
::-------------------------B/T------------------------
::
::
:::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
:::
::::
::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
::::
::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
::::
::::
::::73's de Edd
::::
::::
:::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
:::::
::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
::::::
::::::
::::::
::::::T.

5/10/2007 7:17:36 PMTex
With a wire connected from the 100k, to the side of the 10k that connects to the red wire on the I.F. coil the reading on pin #4 is minus 7.5dc. The radio receiving radio does now whistle up & down the dial.

:Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.
:
:73's de Edd
:
:----------------------------------------------------------------------------------B/T-----------------------------------------------------
:
::I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
::
:::
:::
:::Step two:
:::
:::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
:::
:::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
:::
:::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
:::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
:::
:::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
:::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
:::
:::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
:::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
:::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
:::
:::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
:::wanting to use this setup for a 455 KC alignment generator.
:::
:::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
:::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
:::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
:::
:::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
:::why they were getting their quirky DVM meter readings while working with AC powered equipment.
:::
:::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
:::
:::AC line voltage...metering oddities....technical referencing:
:::
:::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
:::
:::73’s de Edd
:::
:::-------------------------B/T------------------------
:::
:::
::::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
::::
:::::
:::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
:::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
:::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
:::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
:::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
:::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
:::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
:::::
:::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
:::::
:::::
:::::73's de Edd
:::::
:::::
::::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
::::::
:::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
:::::::
:::::::
:::::::
:::::::T.

5/11/2007 11:14:08 AMTex
I put the receiving radio on a unused spot to 550
near 550, which is about 630. The station at 550 can still be heard up that point. I turned the screws on top of the transformer with a homemade plastic screwdriver to get the least amount of hum on each. I removed the jumper and touched the end of the resistor, there was a change in the hum of the receiving radio.
:Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.
:
:73's de Edd
:
:----------------------------------------------------------------------------------B/T-----------------------------------------------------
:
::I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
::
:::
:::
:::Step two:
:::
:::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
:::
:::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
:::
:::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
:::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
:::
:::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
:::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
:::
:::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
:::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
:::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
:::
:::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
:::wanting to use this setup for a 455 KC alignment generator.
:::
:::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
:::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
:::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
:::
:::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
:::why they were getting their quirky DVM meter readings while working with AC powered equipment.
:::
:::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
:::
:::AC line voltage...metering oddities....technical referencing:
:::
:::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
:::
:::73’s de Edd
:::
:::-------------------------B/T------------------------
:::
:::
::::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
::::
:::::
:::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
:::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
:::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
:::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
:::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
:::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
:::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
:::::
:::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
:::::
:::::
:::::73's de Edd
:::::
:::::
::::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
::::::
:::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
:::::::
:::::::
:::::::
:::::::T.
5/11/2007 2:24:26 PMEdd
O.K. ..then, what you have confirmed up to now is that all is in order with your components, construction and tube since you are able to touch its scren grid and get a modulated "hum" put on that RF carrier . So the only fallacy now seems to be that osc transformer that you opted...chanced out?..in receiving and trying to use. Seems like it is either, not working in this circuit ...OR... that its operating waaaaaaaay out in left field, frequency wise, from what you were expecting. Another thing which you should have noticed within your evaluation of an operating circuit is the degree of RF output enhancement that the addition of screen voltage affords to the units RF output level. Basically the unit is creating nothing spectacular in RF output level until the + swinging modulation of the audio source is applied. In which case the incoming audio is swinging up and down in levels and the screen grid receives that and puts out its modulated RF envelope tracking that varying AF signal.
With that close coupling ....via jumper lead(s)....of the unit to the receiver, you certainly noticed the difference in the received signal with the screen grid either connected to your mod pot...or eventually just floating free....both conditions creating a somewhat weak signal level....HOWEVER...when you touched that floating 100k to B+ ti bias up the screen grid, the level took off like GANGBUSTERS.

Plus, that lets you see the potential degree of peak voltage swing that might be required to fully modulate that carrier via the utilization of screen grid modulation. And now, with your having an actual working osc circuit to experimant with, you might go back and wire in your modulation pot and its wiring and then evaluate the unit using your initially mentioned audio sourcing for modulation. Having that close coupling of the unit to the receive radio with the jumper leads will let you easily hear every little nuance of the received signal in order to evaluate the effectiveness of the level of modulation that will be aforded with your audio source level.

From my eng breadboard circuit evaluation of this circuit, it seems that an additional triode or pentode tube might be required to be incorparated into the circuitry as an audio preamp in order to get the degree of voltage swing required for the oscillators screen grid. That being, if one was wanting to use a weaker incoming audio signal...in the 1voltP/P or so level...such as tape players, tuners, CD's typically have as their average output levels.....But you go ahead and try what you was initially trying to use and see if the modulated/and/transmitted RF -----------> received audio level is adequate.

My last thought after the above is done , would be the going back to your original coil and using the osc circuit test condition of having the mod control wiring stripped from the screen circuitry. Then use the 100k from the screen grid to the lower B+ level.
In that hook up, you will have the most active oscillator circuit with the greater potential of the circuit more readily kicking into an oscillating conditon.
Then you could try the original coil again with your new experience in hand and see if it will oscillate..

Then, I think you know the drill....that of trying out the 4 possible conditions of coil windings.
Basically:
Wire the larger inductor in as the plate circuit inductor and the smaller inductor into the grid circuitry .
Power up and DVM see if multiple negative volts DC are present on the first grid...if not, transpose the leads on the coil that is the easiest to work with . Power up and check first grid again. If you got negative voltage ...hunt for your signal on the receiver, which I believe that you found that it was easier to differentiate between received signals if your added finger capacitance to the grid coupling cap and "squegged" the osc signal to make a corresponding noise in the receiver.
Of course the other option, if not oscillating by now was the use of the smaller inductor in the plate circuitry and the larger one in the grid circuitry...then test for osc / neg grid bias......or the sole final possibility of the transposing of a single coils windings leads.

If that original coil still doesn't oscillate....nor fall within your desired frequency...more work is in order.

73's de Edd


--------------------------------------------------------------B/T---------------------------------------------------------------------------

:I put the receiving radio on a unused spot to 550
:near 550, which is about 630. The station at 550 can still be heard up that point. I turned the screws on top of the transformer with a homemade plastic screwdriver to get the least amount of hum on each. I removed the jumper and touched the end of the resistor, there was a change in the hum of the receiving radio.
::Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.
::
::73's de Edd
::
::----------------------------------------------------------------------------------B/T-----------------------------------------------------
::
:::I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
:::
::::
::::
::::Step two:
::::
::::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
::::
::::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
::::
::::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
::::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
::::
::::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
::::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
::::
::::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
::::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
::::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
::::
::::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
::::wanting to use this setup for a 455 KC alignment generator.
::::
::::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
::::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
::::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
::::
::::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
::::why they were getting their quirky DVM meter readings while working with AC powered equipment.
::::
::::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
::::
::::AC line voltage...metering oddities....technical referencing:
::::
::::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
::::
::::73’s de Edd
::::
::::-------------------------B/T------------------------
::::
::::
:::::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
:::::
::::::
::::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
::::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
::::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
::::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
::::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
::::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
::::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
::::::
::::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
::::::
::::::
::::::73's de Edd
::::::
::::::
:::::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
:::::::
::::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
::::::::
::::::::
::::::::
::::::::T.

5/13/2007 11:28:30 AMTex
I now have a working transmitter. The sound in the receiver is weak. I swithched back to the original coil with a 100K resistor in the circuit inplace of the pot. The 1st. grid voltage is -.51, switched the wires on one of the coils, voltage is the same. Switched the wires from one coil to the other voltage is -.52. Earlier I said the I.F. coil was from a GE c240, based on the printing on the back. I now think that it is a GE 102 based on pictures posted on a web site.

:O.K. ..then, what you have confirmed up to now is that all is in order with your components, construction and tube since you are able to touch its scren grid and get a modulated "hum" put on that RF carrier . So the only fallacy now seems to be that osc transformer that you opted...chanced out?..in receiving and trying to use. Seems like it is either, not working in this circuit ...OR... that its operating waaaaaaaay out in left field, frequency wise, from what you were expecting. Another thing which you should have noticed within your evaluation of an operating circuit is the degree of RF output enhancement that the addition of screen voltage affords to the units RF output level. Basically the unit is creating nothing spectacular in RF output level until the + swinging modulation of the audio source is applied. In which case the incoming audio is swinging up and down in levels and the screen grid receives that and puts out its modulated RF envelope tracking that varying AF signal.
:With that close coupling ....via jumper lead(s)....of the unit to the receiver, you certainly noticed the difference in the received signal with the screen grid either connected to your mod pot...or eventually just floating free....both conditions creating a somewhat weak signal level....HOWEVER...when you touched that floating 100k to B+ ti bias up the screen grid, the level took off like GANGBUSTERS.
:
:Plus, that lets you see the potential degree of peak voltage swing that might be required to fully modulate that carrier via the utilization of screen grid modulation. And now, with your having an actual working osc circuit to experimant with, you might go back and wire in your modulation pot and its wiring and then evaluate the unit using your initially mentioned audio sourcing for modulation. Having that close coupling of the unit to the receive radio with the jumper leads will let you easily hear every little nuance of the received signal in order to evaluate the effectiveness of the level of modulation that will be aforded with your audio source level.
:
:From my eng breadboard circuit evaluation of this circuit, it seems that an additional triode or pentode tube might be required to be incorparated into the circuitry as an audio preamp in order to get the degree of voltage swing required for the oscillators screen grid. That being, if one was wanting to use a weaker incoming audio signal...in the 1voltP/P or so level...such as tape players, tuners, CD's typically have as their average output levels.....But you go ahead and try what you was initially trying to use and see if the modulated/and/transmitted RF -----------> received audio level is adequate.
:
:My last thought after the above is done , would be the going back to your original coil and using the osc circuit test condition of having the mod control wiring stripped from the screen circuitry. Then use the 100k from the screen grid to the lower B+ level.
:In that hook up, you will have the most active oscillator circuit with the greater potential of the circuit more readily kicking into an oscillating conditon.
:Then you could try the original coil again with your new experience in hand and see if it will oscillate..
:
:Then, I think you know the drill....that of trying out the 4 possible conditions of coil windings.
:Basically:
:Wire the larger inductor in as the plate circuit inductor and the smaller inductor into the grid circuitry .
:Power up and DVM see if multiple negative volts DC are present on the first grid...if not, transpose the leads on the coil that is the easiest to work with . Power up and check first grid again. If you got negative voltage ...hunt for your signal on the receiver, which I believe that you found that it was easier to differentiate between received signals if your added finger capacitance to the grid coupling cap and "squegged" the osc signal to make a corresponding noise in the receiver.
:Of course the other option, if not oscillating by now was the use of the smaller inductor in the plate circuitry and the larger one in the grid circuitry...then test for osc / neg grid bias......or the sole final possibility of the transposing of a single coils windings leads.
:
:If that original coil still doesn't oscillate....nor fall within your desired frequency...more work is in order.
:
:73's de Edd
:
:
:--------------------------------------------------------------B/T---------------------------------------------------------------------------
:
::I put the receiving radio on a unused spot to 550
::near 550, which is about 630. The station at 550 can still be heard up that point. I turned the screws on top of the transformer with a homemade plastic screwdriver to get the least amount of hum on each. I removed the jumper and touched the end of the resistor, there was a change in the hum of the receiving radio.
:::Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.
:::
:::73's de Edd
:::
:::----------------------------------------------------------------------------------B/T-----------------------------------------------------
:::
::::I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
::::
:::::
:::::
:::::Step two:
:::::
:::::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
:::::
:::::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
:::::
:::::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
:::::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
:::::
:::::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
:::::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
:::::
:::::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
:::::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
:::::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
:::::
:::::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
:::::wanting to use this setup for a 455 KC alignment generator.
:::::
:::::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
:::::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
:::::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
:::::
:::::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
:::::why they were getting their quirky DVM meter readings while working with AC powered equipment.
:::::
:::::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
:::::
:::::AC line voltage...metering oddities....technical referencing:
:::::
:::::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
:::::
:::::73’s de Edd
:::::
:::::-------------------------B/T------------------------
:::::
:::::
::::::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
::::::
:::::::
:::::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
:::::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
:::::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
:::::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
:::::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
:::::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
:::::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
:::::::
:::::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
:::::::
:::::::
:::::::73's de Edd
:::::::
:::::::
::::::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
::::::::
:::::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
:::::::::
:::::::::
:::::::::
:::::::::T.

5/13/2007 5:43:52 PMEdd
It just sounds like the circuit just doesn't like either your coils, inductance values / "Q's" /coupling , but with that VERY low developed first grid voltage in the circuit it seems like all of those factors. And either you are now picking up a weak harmonic of its output or it possibly it just might be puting out waaaaaay lower in frequency than expected. Even your "testing" IF transformer worked appreciably better.
FIO...if that is a Gentle Electric of that series mentione and marked with part number.. they were:
Models 102 and 113 used STL-007 1st IF and STL-008 2nd IF
Models 112 .............. used STL-007 1st IF and STL-015 2nd IF
Model 200 .............. used RTL-001 1st IF and RTL-029 2nd IF
Model 210 .............. used RTL-078 1st IF and RTO-054 2nd IF
So if your IF's part number is one of those, it validates with it being a GE part number of those series.
Since you now have the set up down to a fine art, I now could only suggest two other alternatives :
1.....Order the RF coil specified in the article and use it.
2....Pull the unit (coil)out of circuit and also pull its SM tuning capacitor and ship to me and I will use my combination of grid dipper, L-C-Q meters,spectrum analyzer, scopes and the built up RF test bed circuit in order to find the units actual resonating frequencies of both coils, along with the option of then paring inductance to get the unit to operate at its best capability and on a BC frequency. I would also need to know your desired frequency.....one that is clear of stations in your receive area.

This situation being if the unit is HIGH in its inductive value, if it happens to be low.... which I don't expect with your given resistance readings of the coils. But at any rate, I couldn't successfully add inductance, nor would it be desirable to try to shift resonance by using an exhorbitantly high value of tuning / resonating capacitor.

If you should opt for the latter, fill in your E-mail query box that is under your sign in name on the next reply, so that I can give you a mailing addee. Cost for a bubble mailer for inter TEXAS should be from about 79 cents to a buck...according to distance.

Thassit

73's de Edd

(*** weakly ??? ......as in below)

:I now have a ***working transmitter. The sound in the receiver is weak. I swithched back to the original coil with a 100K resistor in the circuit inplace of the pot. The 1st. grid voltage is -.51, switched the wires on one of the coils, voltage is the same. Switched the wires from one coil to the other voltage is -.52. Earlier I said the I.F. coil was from a GE c240, based on the printing on the back. I now think that it is a GE 102 based on pictures posted on a web site.
:
::O.K. ..then, what you have confirmed up to now is that all is in order with your components, construction and tube since you are able to touch its scren grid and get a modulated "hum" put on that RF carrier . So the only fallacy now seems to be that osc transformer that you opted...chanced out?..in receiving and trying to use. Seems like it is either, not working in this circuit ...OR... that its operating waaaaaaaay out in left field, frequency wise, from what you were expecting. Another thing which you should have noticed within your evaluation of an operating circuit is the degree of RF output enhancement that the addition of screen voltage affords to the units RF output level. Basically the unit is creating nothing spectacular in RF output level until the + swinging modulation of the audio source is applied. In which case the incoming audio is swinging up and down in levels and the screen grid receives that and puts out its modulated RF envelope tracking that varying AF signal.
::With that close coupling ....via jumper lead(s)....of the unit to the receiver, you certainly noticed the difference in the received signal with the screen grid either connected to your mod pot...or eventually just floating free....both conditions creating a somewhat weak signal level....HOWEVER...when you touched that floating 100k to B+ ti bias up the screen grid, the level took off like GANGBUSTERS.
::
::Plus, that lets you see the potential degree of peak voltage swing that might be required to fully modulate that carrier via the utilization of screen grid modulation. And now, with your having an actual working osc circuit to experimant with, you might go back and wire in your modulation pot and its wiring and then evaluate the unit using your initially mentioned audio sourcing for modulation. Having that close coupling of the unit to the receive radio with the jumper leads will let you easily hear every little nuance of the received signal in order to evaluate the effectiveness of the level of modulation that will be aforded with your audio source level.
::
::From my eng breadboard circuit evaluation of this circuit, it seems that an additional triode or pentode tube might be required to be incorparated into the circuitry as an audio preamp in order to get the degree of voltage swing required for the oscillators screen grid. That being, if one was wanting to use a weaker incoming audio signal...in the 1voltP/P or so level...such as tape players, tuners, CD's typically have as their average output levels.....But you go ahead and try what you was initially trying to use and see if the modulated/and/transmitted RF -----------> received audio level is adequate.
::
::My last thought after the above is done , would be the going back to your original coil and using the osc circuit test condition of having the mod control wiring stripped from the screen circuitry. Then use the 100k from the screen grid to the lower B+ level.
::In that hook up, you will have the most active oscillator circuit with the greater potential of the circuit more readily kicking into an oscillating conditon.
::Then you could try the original coil again with your new experience in hand and see if it will oscillate..
::
::Then, I think you know the drill....that of trying out the 4 possible conditions of coil windings.
::Basically:
::Wire the larger inductor in as the plate circuit inductor and the smaller inductor into the grid circuitry .
::Power up and DVM see if multiple negative volts DC are present on the first grid...if not, transpose the leads on the coil that is the easiest to work with . Power up and check first grid again. If you got negative voltage ...hunt for your signal on the receiver, which I believe that you found that it was easier to differentiate between received signals if your added finger capacitance to the grid coupling cap and "squegged" the osc signal to make a corresponding noise in the receiver.
::Of course the other option, if not oscillating by now was the use of the smaller inductor in the plate circuitry and the larger one in the grid circuitry...then test for osc / neg grid bias......or the sole final possibility of the transposing of a single coils windings leads.
::
::If that original coil still doesn't oscillate....nor fall within your desired frequency...more work is in order.
::
::73's de Edd
::
::
::--------------------------------------------------------------B/T---------------------------------------------------------------------------
::
:::I put the receiving radio on a unused spot to 550
:::near 550, which is about 630. The station at 550 can still be heard up that point. I turned the screws on top of the transformer with a homemade plastic screwdriver to get the least amount of hum on each. I removed the jumper and touched the end of the resistor, there was a change in the hum of the receiving radio.
::::Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.
::::
::::73's de Edd
::::
::::----------------------------------------------------------------------------------B/T-----------------------------------------------------
::::
:::::I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
:::::
::::::
::::::
::::::Step two:
::::::
::::::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
::::::
::::::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
::::::
::::::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
::::::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
::::::
::::::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
::::::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
::::::
::::::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
::::::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
::::::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
::::::
::::::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
::::::wanting to use this setup for a 455 KC alignment generator.
::::::
::::::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
::::::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
::::::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
::::::
::::::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
::::::why they were getting their quirky DVM meter readings while working with AC powered equipment.
::::::
::::::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
::::::
::::::AC line voltage...metering oddities....technical referencing:
::::::
::::::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
::::::
::::::73’s de Edd
::::::
::::::-------------------------B/T------------------------
::::::
::::::
:::::::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
:::::::
::::::::
::::::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
::::::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
::::::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
::::::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
::::::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
::::::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
::::::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
::::::::
::::::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
::::::::
::::::::
::::::::73's de Edd
::::::::
::::::::
:::::::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
:::::::::
::::::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
::::::::::
::::::::::
::::::::::
::::::::::T.

5/13/2007 10:47:56 PMTex
I can't express how much I sincerely appreciate the help you have given me. Even with my limited learning abilities, I beleive I have learned from your advice. I'm going to order the coil specified in the article tomorrow. Thank you so very much.

:It just sounds like the circuit just doesn't like either your coils, inductance values / "Q's" /coupling , but with that VERY low developed first grid voltage in the circuit it seems like all of those factors. And either you are now picking up a weak harmonic of its output or it possibly it just might be puting out waaaaaay lower in frequency than expected. Even your "testing" IF transformer worked appreciably better.
:FIO...if that is a Gentle Electric of that series mentione and marked with part number.. they were:
:Models 102 and 113 used STL-007 1st IF and STL-008 2nd IF
:Models 112 .............. used STL-007 1st IF and STL-015 2nd IF
:Model 200 .............. used RTL-001 1st IF and RTL-029 2nd IF
:Model 210 .............. used RTL-078 1st IF and RTO-054 2nd IF
:So if your IF's part number is one of those, it validates with it being a GE part number of those series.
:Since you now have the set up down to a fine art, I now could only suggest two other alternatives :
:1.....Order the RF coil specified in the article and use it.
:2....Pull the unit (coil)out of circuit and also pull its SM tuning capacitor and ship to me and I will use my combination of grid dipper, L-C-Q meters,spectrum analyzer, scopes and the built up RF test bed circuit in order to find the units actual resonating frequencies of both coils, along with the option of then paring inductance to get the unit to operate at its best capability and on a BC frequency. I would also need to know your desired frequency.....one that is clear of stations in your receive area.
:
:This situation being if the unit is HIGH in its inductive value, if it happens to be low.... which I don't expect with your given resistance readings of the coils. But at any rate, I couldn't successfully add inductance, nor would it be desirable to try to shift resonance by using an exhorbitantly high value of tuning / resonating capacitor.
:
:If you should opt for the latter, fill in your E-mail query box that is under your sign in name on the next reply, so that I can give you a mailing addee. Cost for a bubble mailer for inter TEXAS should be from about 79 cents to a buck...according to distance.
:
:Thassit
:
:73's de Edd
:
:(*** weakly ??? ......as in below)
:
:
:
::I now have a ***working transmitter. The sound in the receiver is weak. I swithched back to the original coil with a 100K resistor in the circuit inplace of the pot. The 1st. grid voltage is -.51, switched the wires on one of the coils, voltage is the same. Switched the wires from one coil to the other voltage is -.52. Earlier I said the I.F. coil was from a GE c240, based on the printing on the back. I now think that it is a GE 102 based on pictures posted on a web site.
::
:::O.K. ..then, what you have confirmed up to now is that all is in order with your components, construction and tube since you are able to touch its scren grid and get a modulated "hum" put on that RF carrier . So the only fallacy now seems to be that osc transformer that you opted...chanced out?..in receiving and trying to use. Seems like it is either, not working in this circuit ...OR... that its operating waaaaaaaay out in left field, frequency wise, from what you were expecting. Another thing which you should have noticed within your evaluation of an operating circuit is the degree of RF output enhancement that the addition of screen voltage affords to the units RF output level. Basically the unit is creating nothing spectacular in RF output level until the + swinging modulation of the audio source is applied. In which case the incoming audio is swinging up and down in levels and the screen grid receives that and puts out its modulated RF envelope tracking that varying AF signal.
:::With that close coupling ....via jumper lead(s)....of the unit to the receiver, you certainly noticed the difference in the received signal with the screen grid either connected to your mod pot...or eventually just floating free....both conditions creating a somewhat weak signal level....HOWEVER...when you touched that floating 100k to B+ ti bias up the screen grid, the level took off like GANGBUSTERS.
:::
:::Plus, that lets you see the potential degree of peak voltage swing that might be required to fully modulate that carrier via the utilization of screen grid modulation. And now, with your having an actual working osc circuit to experimant with, you might go back and wire in your modulation pot and its wiring and then evaluate the unit using your initially mentioned audio sourcing for modulation. Having that close coupling of the unit to the receive radio with the jumper leads will let you easily hear every little nuance of the received signal in order to evaluate the effectiveness of the level of modulation that will be aforded with your audio source level.
:::
:::From my eng breadboard circuit evaluation of this circuit, it seems that an additional triode or pentode tube might be required to be incorparated into the circuitry as an audio preamp in order to get the degree of voltage swing required for the oscillators screen grid. That being, if one was wanting to use a weaker incoming audio signal...in the 1voltP/P or so level...such as tape players, tuners, CD's typically have as their average output levels.....But you go ahead and try what you was initially trying to use and see if the modulated/and/transmitted RF -----------> received audio level is adequate.
:::
:::My last thought after the above is done , would be the going back to your original coil and using the osc circuit test condition of having the mod control wiring stripped from the screen circuitry. Then use the 100k from the screen grid to the lower B+ level.
:::In that hook up, you will have the most active oscillator circuit with the greater potential of the circuit more readily kicking into an oscillating conditon.
:::Then you could try the original coil again with your new experience in hand and see if it will oscillate..
:::
:::Then, I think you know the drill....that of trying out the 4 possible conditions of coil windings.
:::Basically:
:::Wire the larger inductor in as the plate circuit inductor and the smaller inductor into the grid circuitry .
:::Power up and DVM see if multiple negative volts DC are present on the first grid...if not, transpose the leads on the coil that is the easiest to work with . Power up and check first grid again. If you got negative voltage ...hunt for your signal on the receiver, which I believe that you found that it was easier to differentiate between received signals if your added finger capacitance to the grid coupling cap and "squegged" the osc signal to make a corresponding noise in the receiver.
:::Of course the other option, if not oscillating by now was the use of the smaller inductor in the plate circuitry and the larger one in the grid circuitry...then test for osc / neg grid bias......or the sole final possibility of the transposing of a single coils windings leads.
:::
:::If that original coil still doesn't oscillate....nor fall within your desired frequency...more work is in order.
:::
:::73's de Edd
:::
:::
:::--------------------------------------------------------------B/T---------------------------------------------------------------------------
:::
::::I put the receiving radio on a unused spot to 550
::::near 550, which is about 630. The station at 550 can still be heard up that point. I turned the screws on top of the transformer with a homemade plastic screwdriver to get the least amount of hum on each. I removed the jumper and touched the end of the resistor, there was a change in the hum of the receiving radio.
:::::Your tuning on the IF adjustments may have left at less than optimal for 455kc if you were thinking being able to tweak them to reach up and create a signal all of the waaaaaay to the low end of the BC band. So proceed directly to the clipping of that free end of that 100k resistor on the screen grid to the reduced B+ source. Then take a derived neg voltage check on the tubes 1st grid and see its value. Perchance the two adjustmnts are so variant, that results are less than optimal,and dampening performance, or action, so do the tuning procedure mentioned.
:::::
:::::73's de Edd
:::::
:::::----------------------------------------------------------------------------------B/T-----------------------------------------------------
:::::
::::::I now have a 100k with one end attached to tube pin #5, the other end of the 100k is loose. The wire from the center lug on the pot is now loose. I disconnected the antenna on the transmitter. I attached two leads to the end of the 220pf & drapped them over the antenna of the receiving radio. I turned the dial on the receiving radio up & down, but didn't hear a whistle also the squeal is gone. Im not sure about the model number of the radio from which I got the I.F. coil. It says c240n on the back of the antenna coil, but some could have switched that. The radio configuration is similiar to a Stewart Warner c51T1, same tubes etc.
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:::::::
:::::::Step two:
:::::::
:::::::Assuming that you now have an operational unit, via the sub in of an IF xformer; with that now being used for a known transformer medium. That now puts your mind at ease about a potential miss wiring, wrong component value (or type), supply voltage problem or a myriad of other minutiae that could potentially throw ones end results for a loop.
:::::::
:::::::Now, hows about developing a stronger concept of its operation while its now in that state of initial operation. Thus having a greater degree of confidence in your RF savvy when incorporating yet another RF coil / transformer for the projects completion. This can be done by the lifting of the wire (at the tubes screen grid pin) that connects over to the modulation level pot.Then tack on one lead of an ~ 1/2watt ~100k resistor to that screen grid pin. Now you probably have taken a DVM enacted voltage reading of the tubes 1st grid voltage and found it now to be up in the ~minus 1.7-3v range [....minus 1.41dc...I see you now say] .So now, in preparation of the next step, place your mentioned larger AC line powered receiver near the xmitter, don't have any rod antenna...if alreaqdy incorporated... hooked up to the unit, but instead, clip on a test lead..or two ?.. to bridge and capacitively couple between the output of the ~220 pf plate / antenna coupling caps floating lead over to the point where you can have the other loose end of that test lead draped and resting upon the receivers loop antenna.
:::::::
:::::::Plus, as I mentioned we are now operating at 455 kc and basically just swamping the receivers front end and having the RF zip right on through the mixer stage and then on into the sets IF strip unimpeded.
:::::::Should you now try tuning the receiver across the band to the point where you will start to tune into an AM radio stations signal its onset will be met with a high shrill "whistle" as the frequency comes within your highest aural hearing range and that frequency will progressively diminish to an ever lower frequency. At the lower spectra it will seem like a "growl' as it scales below the 500~ tonal range. Finally it becomes an ever slower pulsating noise as you are down below 10~ and finally the two frequencies will be coincident with no apparent sound at all, with the "beat" frequency going well below your ears lower hearing range capability. Then, with a further tuning, the effect reverts with the onset of the "growl" and then the progressively onset of an ever higher frequency again until on beyond your highest hearing range capability as was before.
:::::::
:::::::Next, you will take yet another loose test lead and make a temp clip on jumpering connection between the free end of the 100k resistor at the tubes screen grid pin and the reduced B+ at the 10K dropping resistor. This should place in the order of ~30 Vdc to your tubes screen circuit and have the oscillator circuit now "screamin'like a banshee". Pulling out ye olde DVM again and enacting a 1st grid voltage reading should potentially find it now up in the order of minus thirty volts...WOWEE...(fifty watts per channel.. Babycakes !)
:::::::As was mentioned in my prior posting, the AM band should now be fully quieted with only the ominous low freq sound of an RF carrier being present, much akin to a mixing of 60 and 120~ frequencies.
:::::::
:::::::Now, I didn't recognize that Gentle Electrics model numbers IF transformer that you are using, but sort of assume it to be an older unit with leads and possibly its tuning adjustment being via dual trimmer caps being atop a larger casing profile of xformer.
:::::::If you will now tune the radio to the 550 end...off from, and not being tuned into any station... and up the volume in order to better listen for the carrier "hum" I mentioned. Now, if you will then trim in one adjustment you should note that the hum will diminish as you get right onto 455kc and then increase as you tune on past it, move back to the very minimal hum "nulling" position. Then move to the other trimmer and do the same thing. Then back to the initial one for a final null.
:::::::BTW...you might have noticed that the freq determining coil/cap combo that is connected to the 1st grid circuitry is the sharpest "nulling", whereas the other coil/cap combo is somewhat more broad in its tuning.
:::::::
:::::::you now have the unit operating back at optimal efficiency, but possibly not being precisely on 455,000~ ...and of no import now...unless you were also to have done the heterodyning for zero beat...as was just mentioned above ... with the radio tuned into a station at 455 x2= 910 kc on your dial...(or even 1365 kc, but that is 5kc off fro beating with any Am station with their assigned 10kc freq slot) But this is not precisely important now...being so, only if a person was
:::::::wanting to use this setup for a 455 KC alignment generator.
:::::::
:::::::Now that you have the unit tuned for optimum, you can now remove that jumper / test lead that was going from the dropped B+ over to the floating 100k on the screen grid. If you will then touch that free lead with a fingertip, you will be injecting
:::::::electrostatically induced "stray 60~ AC line voltage" that your little ? body / "antenna" is picking up at all times. That action should result in a hum being modulated onto your RF signal and being heard over at the receiver, quite well, when you are touching the lead.
:::::::Akin to the like "no frills" test procedure of doing the same in touching the high side of the volume control and listening to the speaker for the resultant hum. That, giving a rapid / rough confirmation of the integrity of a sets 1st audio stage, its proper coupling, the AF output stage and its output transformer as well as the sets speaker, along with all interconnects and B+ supply....all done with just a mere finger touch.
:::::::
:::::::Just as a bonus... no extra charge... I will include this info that I threw to some MIT collegiate techies, elsewhere, on
:::::::why they were getting their quirky DVM meter readings while working with AC powered equipment.
:::::::
:::::::Now, as you can see, it is working to your advantage in getting a nano-ampere level of test signal to fully modulate your screen grid of the xmitter. BUT you are going to have a somewhat healthy audio voltage level to modulate your unit, which might involve using a small transistor radio transformer salvaged from a scrap set, or new from Radius Shackamus. Where it would be used backwards mode in taking the relatively low Z from a transistor radio and upping the Z to get a higher voltage level to feed to the screen grid circuitry.
:::::::
:::::::AC line voltage...metering oddities....technical referencing:
:::::::
:::::::http://img338.imageshack.us/img338/3285/flukelkgphotosyl1.jpg
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:::::::73’s de Edd
:::::::
:::::::-------------------------B/T------------------------
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:::::::
::::::::This afternoon I was messing around, turning the screws on top of the transformer, now the squeal is at about 580. I squeezed & released the 68pf & it does affect the squeal. The meter reading from tube pin #4 & grnd is minus 1.41dc, from pin #5 to grnd it is minus .41dc. When I touch the voltmeter probes to tube pin #4 & to grnd., I can hear the source in the receiving radio with the receiving radio set at 580.
::::::::
:::::::::
:::::::::Hey...it sounds like you finally have an RF signal being generated now, for all of your extensive efforts.
:::::::::you can confirm that is the signal that you created by merely gripping- releasing the now insulated grid
:::::::::coupling capacitor or a light touching with the fingertip to the lead should create a wild frequency shift.
:::::::::Which should be detected on the mon-receiver., Or you could just turn off the power, but it may take decades of seconds for the B+ to be fully pulled down by the units consumption due to that electrolytics value on the second section of the power supply filtering....heck it might stop first due to its filament cool down.
:::::::::I do believe that if you will check across the dial, that the created RF signal should be stronger at 910 khz,on the signals second harmonic (455 X2= 910) than the apparent 3rd harmonic that you are finding (455X3=1365)
:::::::::at 1365 KHZ. In my test the base generated frequency of 455 was just soaking in through the mixer stage and its creating little squeals "birdies".."heterodynes") as each station was tuned into and passed by.
:::::::::Have you yet..or can you check your first grid DC negative voltage as referenced to ground ?
:::::::::
:::::::::Sorry for the delay on the comeback as, the thread split into two directions and I did not see your reply until just now.
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:::::::::
:::::::::73's de Edd
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:::::::::
::::::::::I wired in an IF transformer from a GE C240. Blue wire to tube pin #3 & ant., red wire to the + side of the electrolytics, yellow wire to the 150pf & continues to gnd & yellow wire also to the 68pf & continues to tube pin #4, green wire to gnd.. When I turn the tuner on the receiving radio & get to about 1400 there is a loud squeal.
::::::::::
:::::::::::Also, if a 12SA7 type coil is used, it must be wired differently, since it often has the secondary in the cathode circuit instead of the plate circuit (such as what would be used with a 6A7 or 6A8).
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:::::::::::T.



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