DuMont 304a oscilloscope

8/25/2009 2:31:46 AMIan

I recently picked up this scope for $.50. I recapped I and checked/ replaced tubes. I have also done most of the alignment. I cannot do the alignment that needs a voltage calibrator or a sine wave or square wave generator. I have two problems, one is that the trace moved up and down on the screen(won't stay centered), second the trace has ripple to it. The manual says to adjust the hum balance control. I can't find it on the scope or on the schematic. Anyone know where to find it on either? OR know how to resolve the centering issue?

Thanks

8/25/2009 11:54:53 AMWarren

Maybe this link will help.

http://docs.google.com/gview?a=v&q=cache:VZZxQNeZybAJ:www.combatindex.com/store/tech_man/Sample/Oscilloscopes/TB_11-6600-254-50.pdf+hum+balance+control+oscilloscope&hl=en&gl=us

8/25/2009 10:41:52 PMIan

That article is probably what I need, however only thr first 3 pages are there I need all of them.

:Maybe this link will help.
:
:http://docs.google.com/gview?a=v&q=cache:VZZxQNeZybAJ:www.combatindex.com/store/tech_man/Sample/Oscilloscopes/TB_11-6600-254-50.pdf+hum+balance+control+oscilloscope&hl=en&gl=us
:

8/26/2009 12:03:23 AMWarren

Don't know about your DuMont model, but on other similar scopes there is a small wire wound pot in there for hum balance control. As far as the jumping around trace, check the control pots with swing needle VTVM. if there dirty or have bad spots, the meter will show it. should be a nice even movement of the needle. also check for ground loops and wire dressing. ground the input to its own ground. should be no ripple showing at all that way. Even sometimes with the case off, the environment it's in will pick up EMI .. It would be nice to have another scope to work on your scope with.

8/26/2009 6:42:26 AMCarl T

Ian,
Have you looked at the manual on BAMA?
I believe it will help you locate the hum control.

http://bama.edebris.com/manuals/dumont/304

Carl T

:That article is probably what I need, however only thr first 3 pages are there I need all of them.
:
:
::Maybe this link will help.
::
::http://docs.google.com/gview?a=v&q=cache:VZZxQNeZybAJ:www.combatindex.com/store/tech_man/Sample/Oscilloscopes/TB_11-6600-254-50.pdf+hum+balance+control+oscilloscope&hl=en&gl=us
::
:

8/26/2009 3:02:24 PMIan

:Yes, that is how I know there is a hum control. only thing is its ot where it says it is. I cant locate it on the schematic either.

When the y input is grounded there is no ripple. Could I boost the values of one of the filter caps, if so which one? there are 5.
Thanks for your help

Ian,
:Have you looked at the manual on BAMA?
:I believe it will help you locate the hum control.
:
:http://bama.edebris.com/manuals/dumont/304
:
:Carl T
:
::That article is probably what I need, however only thr first 3 pages are there I need all of them.
::
::
:::Maybe this link will help.
:::
:::http://docs.google.com/gview?a=v&q=cache:VZZxQNeZybAJ:www.combatindex.com/store/tech_man/Sample/Oscilloscopes/TB_11-6600-254-50.pdf+hum+balance+control+oscilloscope&hl=en&gl=us
:::
::
:

8/26/2009 3:24:20 PMWarren

When you ground the input, then showing no ripple, your power supply is working the way it should. What voltage setting are you using? if it's on the lowest setting, it will pick up noise right out of the air. Might check the probe you are using too. The shield ( ground side ) does need to be going to a good ground connection at the probe end. Better be using an isolation transformer too on any of your radio projects.

8/26/2009 3:40:40 PMIan

I dont think my power supply is 100%, is it possible that the regulator for the +110 volts (verticle plate voltage) is defective? It glows but it seems this would be a cause for random verticle displacement, and ripple of the trace.

On all voltage setting there is ripple, on .1 volts it is over 2 inches , on 100v it is .2 inches.

As for the isolation transformer, I have never repaired a AA5 or hot chassis radio. All of mine are prewar.

:When you ground the input, then showing no ripple, your power supply is working the way it should. What voltage setting are you using? if it's on the lowest setting, it will pick up noise right out of the air. Might check the probe you are using too. The shield ( ground side ) does need to be going to a good ground connection at the probe end. Better be using an isolation transformer too on any of your radio projects.

8/26/2009 4:28:14 PMWarren

I think what you have for the 110 regulator, is a cold cathode gas diode, or rectifier. Such as an 0Z4 found in auto mobile radios. If the voltage is 110 volts it's most likely okay.

8/27/2009 4:41:26 PMEdd

Sir Ian. . . .

I was just examining your initial referencing to HUM BUCKING, and would assume that you were comparing scope circitry to an audio
amp where there is a pot across the filament and setting the center tap grounding can null out hum pickup.

On that scope, I thought that I used to have the same unit hard cable connected up, for using as the display to a bench set up for the sweep alignment of 70 mhz radar IF strips, but, no, I see now that I was using a Whoolet Plastered 130 series.

Sounds like to me that you ought to check out the filtering on the power supply. With that high level pollution of the trace, sounds like its early in the stages of the Y / Vert amplifier section.

Consult the supplied schematic blow-up and note the initial input into the vertical amp section via the red circled BNC (or possubly an older SO) connector.
With that shorted across you should be getting nothing vertically amplified as a display.

The input signal is then differentated by the use of the input switch such as to whether to be in either the AC input mode or the straight DC mode via the switched in coupling capacitor.[Blue-green markup]

The signal is then processed thru cascaded sets of 5 differential amps in the form of V1-V4 pairs and then a final deflection plate driver pair in the form of V5/6.

Now, take note of the markup of the B+ supply levels to those stages, with the highest buss from the buss deriving power from the 5Y3. . . . [RED BUSS]

Then the sub B+ level is being marked up as the [FUSCIA], that is the supply for the lower level amps, with the supply being derived and dropped from the main buss just mentioned. And yes, the sets OBie Kanobie 2 gas regulator tube on that line is working , since you see its glow from the top . . .(since it is not silvered up inside the envelope and you can ACTUALLY see it).

Now, since the whole string of the amps are direct DC coupled you will see the end of the common cathodes of the 6AQ5's with the supply for the earler plates supplies being derived there AND with that all import C8 filter [RED MARKUP . . 3 red squares] being important for the DC purity of the plate supply busses for those earlier preamp stages.

Be sure if it . . . . and a bit less important, is the earlier main B+ filtering at the 5Y3 at its [RED MARKUP . .1 and 2 squares] being in the form of C39 and 40.

Another thought would be the possibility of fil- cathode leakage in the V1 thru 3 preamp tube stages, but I think that it would have made your quiescent trace positioning a bit squirrely or off of scale.

Swap tubes positioning and see if your problem changes in amplitude, . . . . or even abates a bit.

I just additionally enhanced other filters used in the set, but the primary ones of suspicion would be the one on the [FUSCIA] and [RED] lined markups.

As far as "calibration" on the unit and with it being a fiffy cent item , but that being well under the typical $20 evaluation for that unit,
I would only check out the VERT DC amplitude calibration. If you will put the hoz timebase in a fast enough speed , greater than I MS,
you would then have a continous line across the scope screen face, instead of a...s.l.o.w.l.y... moving trace from left to right, whereas in the other aspect, if you set it in its fastest range, the brightness of the trace would be diminishing.

Soooo what you do now is position the trace to the bottom line graticule of the gridwork and then put the vert input sensitivity to 1 v
per CM switch cal setting. You then put a 5VDC reference voltage ( confirmed with your DVM) to the vert input connector and confirm if the sweep jumps upwards to the 5 CM graticule line. If so, you are all right, if not the cal for that decade needs set a bit,

Same procedure for the other decades, but using correspondingly different referrence voltages.

The inherent trace width of a scope line, precludes ascerataining any REAL accuracy on readings anyhow.

Lastly, as per the "only using on old radios", this unit, with its limited 100's of KC's bandwidth would only suffice for that type of service or for audio display . . . .or as a display on a sweep alignment setup.

73's de Edd

Dumont Scope Schematic Mark-up:

8/27/2009 4:54:57 PM . . . a massive flying "colons" attack trashed up text right indexing . . .

Sir Ian. . . .

I was just examining your initial referencing to HUM BUCKING, and would assume that you were comparing scope circitry to an audio amp where there is a pot across the filament and setting the center tap grounding can null out hum pickup.

On that scope, I thought that I used to have the same unit hard cable connected up, for using as the display to a bench set up for the sweep alignment of 70 mhz radar IF strips, but, no, I see now that I was using a Whoolet Plastered 130 series.

Sounds like to me that you ought to check out the filtering on the power supply. With that high level pollution of the trace, sounds like its early in the stages of the Y / Vert amplifier section.

Consult the supplied schematic blow-up and note the initial input into the vertical amp section via the red circled BNC (or possubly an older SO) connector.
With that shorted across you should be getting nothing vertically amplified as a display.

The input signal is then differentated by the use of the input switch such as to whether to be in either the AC input mode or the straight DC mode via the switched in coupling capacitor.[Blue-green markup]

The signal is then processed thru cascaded sets of 5 differential amps in the form of V1-V4 pairs and then a final deflection plate driver pair in the form of V5/6.

Now, take note of the markup of the B+ supply levels to those stages, with the highest buss from the buss deriving power from the 5Y3. . . . [RED BUSS]

Then the sub B+ level is being marked up as the [FUSCIA], that is the supply for the lower level amps, with the supply being derived and dropped from the main buss just mentioned. And yes, the sets OBie Kanobie 2 gas regulator tube on that line is working , since you see its glow from the top . . .(since it is not silvered up inside the envelope and you can ACTUALLY see it).

Now, since the whole string of the amps are direct DC coupled you will see the end of the common cathodes of the 6AQ5's with the supply for the earler plates supplies being derived there AND with that all import C8 filter [RED MARKUP . . 3 red squares] being important for the DC purity of the plate supply busses for those earlier preamp stages.

Be sure if it . . . . and a bit less important, is the earlier main B+ filtering at the 5Y3 at its [RED MARKUP . .1 and 2 squares] being in the form of C39 and 40.

I just additionally enhanced other filters used in the set, but the primary ones of suspicion would be the one on the [FUSCIA] and [RED] lined markups.

As far as "calibration" on the unit and with it being a fiffy cent item , but that being well under the typical $20 evaluation for that unit,
I would only check out the VERT DC amplitude calibration. If you will put the hoz timebase in a fast enough speed , greater than I MS,
you would then have a continous line across the scope screen face, instead of a...s.l.o.w.l.y... moving trace from left to right, whereas in the other aspect, if you set it in its fastest range, the brightness of the trace would be diminishing.

Soooo what you do now is position the trace to the bottom line graticule of the gridwork and then put the vert input sensitivity to 1 v
per CM switch cal setting. You then put a 5VDC reference voltage ( confirmed with your DVM) to the vert input connector and confirm if the sweep jumps upwards to the 5 CM graticule line. If so, you are all right, if not the cal for that decade needs set a bit,

Same procedure for the other decades, but using correspondingly different reference voltages.

The inherent trace width of a scope line, precludes ascertaining any REAL accuracy on readings anyhow.

Lastly, as per the "only using on old radios", this unit, with its limited 100's of KC's bandwidth would only suffice for that type of service or for audio display . . . .or as a display on a sweep alignment setup.

73's de Edd

Dumont Scope Schematic Mark-up:

8/27/2009 5:01:04 PM . .still

Sir Ian. . . .

I was just examining your initial referencing to HUM BUCKING, and would assume that you were comparing scope circitry to an audio amp where there is a pot across the filament and setting the center tap grounding can null out hum pickup.

On that scope, I thought that I used to have the same unit hard cable connected up, for using as the display to a bench set up for the sweep alignment of 70 mhz radar IF strips, but, no, I see now that I was using a Whoolet Plastered 130 series.

Sounds like to me that you ought to check out the filtering on the power supply. With that high level pollution of the trace, sounds like its early in the stages of the Y / Vert amplifier section.

Consult the supplied schematic blow-up and note the initial input into the vertical amp section via the red circled BNC (or possubly an older SO) connector.
With that shorted across you should be getting nothing vertically amplified as a display.

The input signal is then differentated by the use of the input switch such as to whether to be in either the AC input mode or the straight DC mode via the switched in coupling capacitor.[Blue-green markup]

The signal is then processed thru cascaded sets of 5 differential amps in the form of V1-V4 pairs and then a final deflection plate driver pair in the form of V5/6.

Now, take note of the markup of the B+ supply levels to those stages, with the highest buss from the buss deriving power from the 5Y3. . . . [RED BUSS]

Then the sub B+ level is being marked up as the [FUSCIA], that is the supply for the lower level amps, with the supply being derived and dropped from the main buss just mentioned. And yes, the sets OBie Kanobie 2 gas regulator tube on that line is working , since you see its glow from the top . . .(since it is not silvered up inside the envelope and you can ACTUALLY see it).

Now, since the whole string of the amps are direct DC coupled you will see the end of the common cathodes of the 6AQ5's with the supply for the earler plates supplies being derived there AND with that all import C8 filter [RED MARKUP . . 3 red squares] being important for the DC purity of the plate supply busses for those earlier preamp stages.

Be sure if it . . . . and a bit less important, is the earlier main B+ filtering at the 5Y3 at its [RED MARKUP . .1 and 2 squares] being in the form of C39 and 40.

I just additionally enhanced other filters used in the set, but the primary ones of suspicion would be the one on the [FUSCIA] and [RED] lined markups.

As far as "calibration" on the unit and with it being a fiffy cent item , but that being well under the typical $20 evaluation for that unit,
I would only check out the VERT DC amplitude calibration. If you will put the hoz timebase in a fast enough speed , greater than I MS,
you would then have a continous line across the scope screen face, instead of a...s.l.o.w.l.y... moving trace from left to right, whereas in the other aspect, if you set it in its fastest range, the brightness of the trace would be diminishing.

Soooo what you do now is position the trace to the bottom line graticule of the gridwork and then put the vert input sensitivity to 1 v
per CM switch cal setting. You then put a 5VDC reference voltage ( confirmed with your DVM) to the vert input connector and confirm if the sweep jumps upwards to the 5 CM graticule line. If so, you are all right, if not the cal for that decade needs set a bit,

Same procedure for the other decades, but using correspondingly different reference voltages.

The inherent trace width of a scope line, precludes ascertaining any REAL accuracy on readings anyhow.

Lastly, as per the "only using on old radios", this unit, with its limited 100's of KC's bandwidth would only suffice for that type of service or for audio display . . . .or as a display on a sweep alignment setup.

73's de Edd

Dumont Scope Schematic Mark-up:

8/28/2009 4:24:57 AM . . . . .al fin ?

Sir Ian. . . .

I was just examining your initial referencing to HUM BUCKING, and would assume that you were comparing scope circitry to an audio amp where there is a pot across the filament and setting the center tap grounding can null out hum.

On that scope, I thought that I used to have the same unit hard cable connected up, for using as the display to a bench set up for the sweep alignment of 70 mhz radar IF strips, but, no, I see now that I was using a Whoolet Plastered 130 series.

Sounds like to me that you ought to check out the filtering on the power supply. With that high level pollution of the trace, sounds like its early in the stages of the Y / Vert amplifier section.

Consult the supplied schematic blow-up and note the initial input into the vertical amp section via the red circled BNC (or possubly an older SO) connector.

With that shorted across you should be getting nothing vertically amplified as a display.

The input signal is then differentated by the use of the input switch such as to whether to be in either the AC input mode or the straight DC mode via the switched in coupling capacitor.[Blue-green markup]

The signal is then processed thru cascaded sets of 5 differential amps in the form of V1-V4 pairs and then a final deflection plate driver pair in the form of V5/6.

Now, take note of the markup of the B+ supply levels to those stages, with the highest buss from the buss deriving power from the 5Y3. . . . [RED BUSS]

Then the sub B+ level is being marked up as the [FUSCIA], that is the supply for the lower level amps, with the supply being derived and dropped from the main buss just mentioned. And yes, the sets OBie Kanobie 2 gas regulator tube on that line is working , since you see its glow from the top . . .(since it is not silvered up inside the envelope and you can ACTUALLY see it).

Now, since the whole string of the amps are direct DC coupled you will see the end of the common cathodes of the 6AQ5's with the supply for the earler plates supplies being derived there AND with that all import C8 filter [RED MARKUP . . 3 red squares] being important for the DC purity of the plate supply busses for those earlier preamp stages.

Be sure if it . . . . and a bit less important, is the earlier main B+ filtering at the 5Y3 at its [RED MARKUP . .1 and 2 squares] being in the form of C39 and 40.

Swap tubes V1-4's positioning and see if your problem changes in amplitude, . . . . or even abates a bit.

I just additionally enhanced other filters used in the set, but the primary ones of suspicion would be the one on the [FUSCIA] and [RED] lined markups.

As far as "calibration" on the unit and with it being a fiffy cent item , but that being well under the typical $20 evaluation for that unit. Yet this unit is head over heels better than an EICO or HEATHKIT of that vintage.

If my unit, my main concern would be checking out the VERT amplitude calibration. If you will put the hoz timebase in a fast enough speed , greater than 1 MS, you would then have a continous line across the scope screen face, instead of a...s.l.o.w.l.y... moving trace from left to right, whereas in the other aspect, if you set it in its fastest range, the brightness of the trace would be diminishing.

Soooo what you do now is position the trace to the bottom line graticule of the gridwork and then put the vert input sensitivity to 1 V per CM switch cal setting.Set the input coupling mode to DC, so that a mere DC voltage level can be used as your cal source.

You then put a 5VDC reference voltage ( confirmed with your DVM) to the vert input connector and confirm if the sweep jumps upwards to the 5 CM graticule line. If so, you are all right, if not, the cal pot for that decade needs set a bit.

Same procedure for the other decades, but using correspondingly different reference voltages.

The inherent trace width of a scope line, precludes ascertaining any REAL accuracy on readings anyhow.

Lastly, as per the "only using on old radios", this unit, with its limited 100's of KC's bandwidth would only suffice for that type of service or for audio display . . . .or as a display on a sweep alignment setup.

73's de Edd

Dumont Scope Schematic Mark-up:

2/13/2014 6:50:15 PMSmoothOscillator

The link for the Dumont 304a is no longer available…looking for the schematic for the version w/1x2 rectifiers and Amperite Ballast tube..
Any help is appreciated

:
:
:
:
:
:Sir Ian. . . .
:
:
:
:I was just examining your initial referencing to HUM BUCKING, and would assume that you were comparing scope circitry to an audio amp where there is a pot across the filament and setting the center tap grounding can null out hum.
:
:
:
:On that scope, I thought that I used to have the same unit hard cable connected up, for using as the display to a bench set up for the sweep alignment of 70 mhz radar IF strips, but, no, I see now that I was using a Whoolet Plastered 130 series.
:
:
:
:Sounds like to me that you ought to check out the filtering on the power supply. With that high level pollution of the trace, sounds like its early in the stages of the Y / Vert amplifier section.
:
:
:
:Consult the supplied schematic blow-up and note the initial input into the vertical amp section via the red circled BNC (or possubly an older SO) connector.
:
:
:With that shorted across you should be getting nothing vertically amplified as a display.
:
:
:
:The input signal is then differentated by the use of the input switch such as to whether to be in either the AC input mode or the straight DC mode via the switched in coupling capacitor.[Blue-green markup]
:
:
:
:The signal is then processed thru cascaded sets of 5 differential amps in the form of V1-V4 pairs and then a final deflection plate driver pair in the form of V5/6.
:
:
:
:Now, take note of the markup of the B+ supply levels to those stages, with the highest buss from the buss deriving power from the 5Y3. . . . [RED BUSS]
:
:
:
:Then the sub B+ level is being marked up as the [FUSCIA], that is the supply for the lower level amps, with the supply being derived and dropped from the main buss just mentioned. And yes, the sets OBie Kanobie 2 gas regulator tube on that line is working , since you see its glow from the top . . .(since it is not silvered up inside the envelope and you can ACTUALLY see it).
:
:
:
:Now, since the whole string of the amps are direct DC coupled you will see the end of the common cathodes of the 6AQ5's with the supply for the earler plates supplies being derived there AND with that all import C8 filter [RED MARKUP . . 3 red squares] being important for the DC purity of the plate supply busses for those earlier preamp stages.
:
:
:
:Be sure if it . . . . and a bit less important, is the earlier main B+ filtering at the 5Y3 at its [RED MARKUP . .1 and 2 squares] being in the form of C39 and 40.
:
:
:
:Another thought would be the possibility of fil- cathode leakage in the V1 thru 3 preamp tube stages, but I think that it would have made your quiescent trace positioning a bit squirrely or off of scale.
:
:
:
:Swap tubes V1-4's positioning and see if your problem changes in amplitude, . . . . or even abates a bit.
:
:
:
:I just additionally enhanced other filters used in the set, but the primary ones of suspicion would be the one on the [FUSCIA] and [RED] lined markups.
:
:
:
:As far as "calibration" on the unit and with it being a fiffy cent item , but that being well under the typical $20 evaluation for that unit. Yet this unit is head over heels better than an EICO or HEATHKIT of that vintage.
:
:
:If my unit, my main concern would be checking out the VERT amplitude calibration. If you will put the hoz timebase in a fast enough speed , greater than 1 MS, you would then have a continous line across the scope screen face, instead of a...s.l.o.w.l.y... moving trace from left to right, whereas in the other aspect, if you set it in its fastest range, the brightness of the trace would be diminishing.
:
:
:
:Soooo what you do now is position the trace to the bottom line graticule of the gridwork and then put the vert input sensitivity to 1 V per CM switch cal setting.Set the input coupling mode to DC, so that a mere DC voltage level can be used as your cal source.
:
:
:
:You then put a 5VDC reference voltage ( confirmed with your DVM) to the vert input connector and confirm if the sweep jumps upwards to the 5 CM graticule line. If so, you are all right, if not, the cal pot for that decade needs set a bit.
:
:
:
:Same procedure for the other decades, but using correspondingly different reference voltages.
:
:
:
:The inherent trace width of a scope line, precludes ascertaining any REAL accuracy on readings anyhow.
:
:
:
:Lastly, as per the "only using on old radios", this unit, with its limited 100's of KC's bandwidth would only suffice for that type of service or for audio display . . . .or as a display on a sweep alignment setup.
:
:
:
:
:
:
:
:
:
:
:73's de Edd
:
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:

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Dumont Scope Schematic Mark-up:
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2/14/2014 11:43:28 AMTry This

:The link for the Dumont 304a is no longer available…looking for the schematic for the version w/1x2 rectifiers and Amperite Ballast tube..
:Any help is appreciated

http://i151.photobucket.com/albums/s130/DXC_alternate/dumont304schematic.png

2/14/2014 4:12:27 PMEdd

Esteemed Sir "Smooth (Parasitic) Oscillator " . . . . . .

It seems like my initial hosting site of that marked up schema, has pulled that info back within in the past years, but thank "goo-ness " Our Honorable . . . .i151 photobucket subscriber . . . aka . . . John K /Kris Kringle / "Ei Fr" . . . . had saved its origins and is now passing it back for our review.

HOWEVER there is being one deficiency, in its not coming to the FULL size that I had initially posted it, when you now dub-L left CURSOR click upon it.

BUT, in reviewing its storage bit density , it see that its dupe is STILL being of adequate pixel count for you to now go to your BROWSERS tool portion and magnify it on up to a 300% size and you will then have a nice viewable schematic.

Since this schema is covering the main DUMONT/FAIRCHILD 304 and its later AH version, you will have to confirm the circuitry design being utilized in your A version set.

The schema shows a " 2X2 " for the upper HV rectifier tube and yet another being wired in down at the bottom on the AH version which would give voltage doubling for feeding the image intensifying ultor.

(MUCH mo-better with that extra hi voltage.)

Surely, the schematics draftsman erroneously marked the two high voltage rectifiers up as 2X2's, while being 1X2's as I find no 2 volt versions ever, in old tube manuals !

1X2's were commonly found in old TV's for their focus rectifier function.

As per that mentioned AMPERITE " ? ? ? ? ballast ? ? ? ? ?" I see no presence on the schematic , HOWEVER on the other boys scopes . . .TEK . . .to wit . . .
liked to use an AMPERITE thermal time delay relay wired to the filament supply for its activation, to finally delay the switching on of the instruments

main B+ to the unit after the filaments had all warmed up to temperature.

Confirm AMPERITE wiring to see if that was what was done on your A version.

Since you NOW have the principal power supply schematic, see how far you can go .
I am available for "consolation" and might even later, dig up its whole manual . . . . somewhere? ? ? ? in my storage archives.

Thasssssit . . . . . .

73's de Edd

GREEN message:

Conserve Toilet Paper . . . use both sides ! ! !

(Expected response ? . . . .Visualizing + wrenching and squirming + eeeeeeeeeeeeeeeeeeeeeeeeeew !)

::The link for the Dumont 304a is no longer available…looking for the schematic for the version w/1x2 rectifiers and Amperite Ballast tube..
::Any help is appreciated
:
:http://i151.photobucket.com/albums/s130/DXC_alternate/dumont304schematic.png
:
:

2/18/2014 9:30:36 PMIan

I stop by for the first time in a few years and one of my threads is on the front page!

@ smooth, I've got parts from few 304's that got scrapped, pm me on ARF (tubeshack)if you need anything.

The 304 this this thread is still alive, but keeps developing issues. It never worked well....

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:Esteemed Sir "Smooth (Parasitic) Oscillator " . . . . . .
:
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:It seems like my initial hosting site of that marked up schema, has pulled that info back within in the past years, but thank "goo-ness " Our Honorable . . . .i151 photobucket subscriber . . . aka . . . John K /Kris Kringle / "Ei Fr" . . . . had saved its origins and is now passing it back for our review.
:
:
:HOWEVER there is being one deficiency, in its not coming to the FULL size that I had initially posted it, when you now dub-L left CURSOR click upon it.
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:BUT, in reviewing its storage bit density , it see that its dupe is STILL being of adequate pixel count for you to now go to your BROWSERS tool portion and magnify it on up to a 300% size and you will then have a nice viewable schematic.
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:Since this schema is covering the main DUMONT/FAIRCHILD 304 and its later AH version, you will have to confirm the circuitry design being utilized in your A version set.
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:The schema shows a " 2X2 " for the upper HV rectifier tube and yet another being wired in down at the bottom on the AH version which would give voltage doubling for feeding the image intensifying ultor.
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: (MUCH mo-better with that extra hi voltage.)
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:Surely, the schematics draftsman erroneously marked the two high voltage rectifiers up as 2X2's, while being 1X2's as I find no 2 volt versions ever, in old tube manuals !
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: 1X2's were commonly found in old TV's for their focus rectifier function.
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:As per that mentioned AMPERITE " ? ? ? ? ballast ? ? ? ? ?" I see no presence on the schematic , HOWEVER on the other boys scopes . . .TEK . . .to wit . . .
: liked to use an AMPERITE thermal time delay relay wired to the filament supply for its activation, to finally delay the switching on of the instruments
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: main B+ to the unit after the filaments had all warmed up to temperature.
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:Confirm AMPERITE wiring to see if that was what was done on your A version.
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:Since you NOW have the principal power supply schematic, see how far you can go .
:I am available for "consolation" and might even later, dig up its whole manual . . . . somewhere? ? ? ? in my storage archives.
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:Thasssssit . . . . . .
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:73's de Edd
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:GREEN message:
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:Conserve Toilet Paper . . . use both sides ! ! !
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:(Expected response ? . . . .Visualizing + wrenching and squirming + eeeeeeeeeeeeeeeeeeeeeeeeeew !)
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:::The link for the Dumont 304a is no longer available…looking for the schematic for the version w/1x2 rectifiers and Amperite Ballast tube..
:::Any help is appreciated
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::http://i151.photobucket.com/albums/s130/DXC_alternate/dumont304schematic.png
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