http://www.nostalgiaair.org/PagesByModel/347/M0009347.pdf
Your radio may not have the 3rd IF transformer. The schematic shows R/C coupling between the 2 6SK7 IF amps. There may have been an IF transformer there in the first productions and later the manufacturer decided to do away with the transformer and use R/C coupling to save money on production.
Radiodoc
*************
::Hello. I must be missing something on the schematic for the Howard 718. The layouts at the bottom indicate that there should be three(its not the same as the layout of the actual chassis, but they should both have three I.F./R.F. transformers as indicated). I cannot seem to locate, by part number, which set of coils on the schematic goes to the "extra" transformer. Help please.
:
:http://www.nostalgiaair.org/PagesByModel/347/M0009347.pdf
Just to add to what Radiodoc says,if you will notice in the parts list, the first IF is 46-936, the second is 54-936, and the third is 47-936. The schematic for 718 series X shows part numbered 54-936 as a capacitor, and a 100,000 ohm resistor between the two 6SK7 tubes, so this probably is not inside an IF can like the other two. I hope this helps,
Doug H.
:Perthrow,
:
:Your radio may not have the 3rd IF transformer. The schematic shows R/C coupling between the 2 6SK7 IF amps. There may have been an IF transformer there in the first productions and later the manufacturer decided to do away with the transformer and use R/C coupling to save money on production.
:
:Radiodoc
:*************
:
:
:::Hello. I must be missing something on the schematic for the Howard 718. The layouts at the bottom indicate that there should be three(its not the same as the layout of the actual chassis, but they should both have three I.F./R.F. transformers as indicated). I cannot seem to locate, by part number, which set of coils on the schematic goes to the "extra" transformer. Help please.
::
::http://www.nostalgiaair.org/PagesByModel/347/M0009347.pdf
I have a third R.F./I.F. transformer IN MY UNIT. I just cant seem to tell which set of coils it is on the schematic
:
:Just to add to what Radiodoc says,if you will notice in the parts list, the first IF is 46-936, the second is 54-936, and the third is 47-936. The schematic for 718 series X shows part numbered 54-936 as a capacitor, and a 100,000 ohm resistor between the two 6SK7 tubes, so this probably is not inside an IF can like the other two. I hope this helps,
:
:Doug H.
:
:
:
:
::Perthrow,
::
::Your radio may not have the 3rd IF transformer. The schematic shows R/C coupling between the 2 6SK7 IF amps. There may have been an IF transformer there in the first productions and later the manufacturer decided to do away with the transformer and use R/C coupling to save money on production.
::
::Radiodoc
::*************
::
::
::::Hello. I must be missing something on the schematic for the Howard 718. The layouts at the bottom indicate that there should be three(its not the same as the layout of the actual chassis, but they should both have three I.F./R.F. transformers as indicated). I cannot seem to locate, by part number, which set of coils on the schematic goes to the "extra" transformer. Help please.
:::
:::http://www.nostalgiaair.org/PagesByModel/347/M0009347.pdf
You should be able to determine the transformer between the two 6SK7s by checking the wiring. I am not sure of the transformer wire colors or whether lugs are used for connecting the transformer to the circuit. One lead of the transformer primary (blue or white lead?) will go to the plate pin 8 of the first 6SK7, one lead of the transformer secondary (green?) will go to the control grid (G1) pin 4 of the second 6SK7.
Radiodoc
************
:No guys, no. I mean i HAVE the transformer IN the unit. It is in the full flesh. It is hardwired in and is supposed to be there. It is original and just as old as the rest of them. What I mean is, I cant seem to tell which one it is supposed to be on the schematic. Im pretty sure about the two I.F.'s, but this one is right between the pentagrid and the first 6SK7, then there is one between that 6SK7 and the next, and then of course after the final 6SK7 and the 6H6 combo detector/AVC.
:I have a third R.F./I.F. transformer IN MY UNIT. I just cant seem to tell which set of coils it is on the schematic
:
:
::
::Just to add to what Radiodoc says,if you will notice in the parts list, the first IF is 46-936, the second is 54-936, and the third is 47-936. The schematic for 718 series X shows part numbered 54-936 as a capacitor, and a 100,000 ohm resistor between the two 6SK7 tubes, so this probably is not inside an IF can like the other two. I hope this helps,
::
::Doug H.
::
::
::
::
:::Perthrow,
:::
:::Your radio may not have the 3rd IF transformer. The schematic shows R/C coupling between the 2 6SK7 IF amps. There may have been an IF transformer there in the first productions and later the manufacturer decided to do away with the transformer and use R/C coupling to save money on production.
:::
:::Radiodoc
:::*************
:::
:::
:::::Hello. I must be missing something on the schematic for the Howard 718. The layouts at the bottom indicate that there should be three(its not the same as the layout of the actual chassis, but they should both have three I.F./R.F. transformers as indicated). I cannot seem to locate, by part number, which set of coils on the schematic goes to the "extra" transformer. Help please.
::::
::::http://www.nostalgiaair.org/PagesByModel/347/M0009347.pdf
Speaking of which, I really dont get some of the audio section. I am supposing my 6SF5 with an extremely low plate voltage is the bass tube, and that the other one going through the 6J5 is the normal one. I could be wrong. I completely understand the function of the inverter. Having some trouble with the tone stack though. I am supposing the 2 meg pot is the volume control and the other two are for tone. Any thoughts?
:Perthrow,
:
:You should be able to determine the transformer between the two 6SK7s by checking the wiring. I am not sure of the transformer wire colors or whether lugs are used for connecting the transformer to the circuit. One lead of the transformer primary (blue or white lead?) will go to the plate pin 8 of the first 6SK7, one lead of the transformer secondary (green?) will go to the control grid (G1) pin 4 of the second 6SK7.
:
:Radiodoc
:************
:
:
::No guys, no. I mean i HAVE the transformer IN the unit. It is in the full flesh. It is hardwired in and is supposed to be there. It is original and just as old as the rest of them. What I mean is, I cant seem to tell which one it is supposed to be on the schematic. Im pretty sure about the two I.F.'s, but this one is right between the pentagrid and the first 6SK7, then there is one between that 6SK7 and the next, and then of course after the final 6SK7 and the 6H6 combo detector/AVC.
::I have a third R.F./I.F. transformer IN MY UNIT. I just cant seem to tell which set of coils it is on the schematic
::
::
:::
:::Just to add to what Radiodoc says,if you will notice in the parts list, the first IF is 46-936, the second is 54-936, and the third is 47-936. The schematic for 718 series X shows part numbered 54-936 as a capacitor, and a 100,000 ohm resistor between the two 6SK7 tubes, so this probably is not inside an IF can like the other two. I hope this helps,
:::
:::Doug H.
:::
:::
:::
:::
::::Perthrow,
::::
::::Your radio may not have the 3rd IF transformer. The schematic shows R/C coupling between the 2 6SK7 IF amps. There may have been an IF transformer there in the first productions and later the manufacturer decided to do away with the transformer and use R/C coupling to save money on production.
::::
::::Radiodoc
::::*************
::::
::::
::::::Hello. I must be missing something on the schematic for the Howard 718. The layouts at the bottom indicate that there should be three(its not the same as the layout of the actual chassis, but they should both have three I.F./R.F. transformers as indicated). I cannot seem to locate, by part number, which set of coils on the schematic goes to the "extra" transformer. Help please.
:::::
:::::http://www.nostalgiaair.org/PagesByModel/347/M0009347.pdf
I think that waaaay back when I initially commented on the set having a tuned RF stage in addition to having TWO I.F.stages I definitely caught the inner stage RC coupling of the two I.F.s, but did not look at the top chassis layout pictorial, at that time,
where there is definitely a 2nd IF transformer shown.
I also, assumed that with the fierce unbridled gain of two pentode IF stages, that they were tailoring down the gain a bit to a controllable level by utilizing that manner of RC interstage coupling.
The supplied schematic reference alteration is probably what you will find the set using in incorporating the second IF transformer shown, with its secondary being tied into the AVC buss ( probably with some alteration of its series supply resistor values) for the gain being controlled or else by a slope tuning of the IF alignment or even a final resistive Q-dampening of x-former windings if finally deemed necessary.
I have even worked with a receiver
that was VERY well designed, RF decoupled and well laid out piece of military equipment, that incorporated 2 tuned front end RF stages and 3 I.F. stages...the BC 348, they pulled out all of the stops for that one.
The other supplied data is within the fill in schematics red mark ups of your query about the functions of the different early stage audio tubes. Along, with their A B phase inverter relationships.
The aspect of the set incorporating (two) 2 meg pots will have to be figured out by yourself after having a working unit in order to play with, and evaluate the controls.
I can see three things..... if the two units are built as one dual pot unit, I can then see a loudness compensation circuitry being incorporated, with it being in circuit at low volume levels to perceive of enhanced bass response.(1)
(1)
(The Fletcher -Munson effect... where the human ear's response curve doesn't pick up low frequencies very well at low volume levels)
The same situation could be true, if two separate pots might happen to be mechanically ganged together via coupled shafts, gearing or tandem coupled dial cord connected /drums.
The third aspect being their utilization as two separate..... vernier volume / volume limit.... controls. The front panel decals might possibly clarify that aspect of utilization.
SCHEMATIC MARKUP…….
73's de Edd
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:I think that waaaay back when I initially commented on the set having a tuned RF stage in addition to having TWO I.F.stages I definitely caught the inner stage RC coupling of the two I.F.s, but did not look at the top chassis layout pictorial, at that time,
: where there is definitely a 2nd IF transformer shown.
:
:
:I also, assumed that with the fierce unbridled gain of two pentode IF stages, that they were tailoring down the gain a bit to a controllable level by utilizing that manner of RC interstage coupling.
:
:
:The supplied schematic reference alteration is probably what you will find the set using in incorporating the second IF transformer shown, with its secondary being tied into the AVC buss ( probably with some alteration of its series supply resistor values) for the gain being controlled or else by a slope tuning of the IF alignment or even a final resistive Q-dampening of x-former windings if finally deemed necessary.
:
:
:I have even worked with a receiver
:that was VERY well designed, RF decoupled and well laid out piece of military equipment, that incorporated 2 tuned front end RF stages and 3 I.F. stages...the BC 348, they pulled out all of the stops for that one.
:
:
:
:The other supplied data is within the fill in schematics red mark ups of your query about the functions of the different early stage audio tubes. Along, with their A B phase inverter relationships.
:
:
:The aspect of the set incorporating (two) 2 meg pots will have to be figured out by yourself after having a working unit in order to play with, and evaluate the controls.
:
:I can see three things..... if the two units are built as one dual pot unit, I can then see a loudness compensation circuitry being incorporated, with it being in circuit at low volume levels to perceive of enhanced bass response.(1)
:
:
:
:(1)
:(The Fletcher -Munson effect... where the human ear's response curve doesn't pick up low frequencies very well at low volume levels)
:
:
:
:The same situation could be true, if two separate pots might happen to be mechanically ganged together via coupled shafts, gearing or tandem coupled dial cord connected /drums.
:
:
:
:The third aspect being their utilization as two separate..... vernier volume / volume limit.... controls. The front panel decals might possibly clarify that aspect of utilization.
:
:
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:SCHEMATIC MARKUP…….
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Goodness. Its a shame I haven't checked this site for a month. I appreciate the time you must have taken out of your day to do this for me.
The two 2 meg volume controls are ganged. Same shafter two pots. Cant understand why they would split it up like that. I can now at least understand the audio section better as far as the "tone stack" is concerned. I wasn't exactly for sure on how the gain was reduced to be fed into the inverter and still a little wierded out by the fact that the screen grid volts are higher than the plate volts on the 6V6GT's. My only other questions for this set are about the loop antenna and where my other coils are at.
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:73's de Edd
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I do appreciate the help given by Edd and others, and I often forget that others don't have a catalogue of the things I understand and the things I don't. You all have been nice and broken down a lot of things for me and it hasn't gone unnoticed.
Edd, where did you find that schematic? I looked at the "518" and it was not the circuit you have depicted so wonderfully in your last post on this subject.
I am still wondering about the screen voltages on the 6V6's and about the loop antenna.
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:I think that waaaay back when I initially commented on the set having a tuned RF stage in addition to having TWO I.F.stages I definitely caught the inner stage RC coupling of the two I.F.s, but did not look at the top chassis layout pictorial, at that time,
: where there is definitely a 2nd IF transformer shown.
:
:
:I also, assumed that with the fierce unbridled gain of two pentode IF stages, that they were tailoring down the gain a bit to a controllable level by utilizing that manner of RC interstage coupling.
:
:
:The supplied schematic reference alteration is probably what you will find the set using in incorporating the second IF transformer shown, with its secondary being tied into the AVC buss ( probably with some alteration of its series supply resistor values) for the gain being controlled or else by a slope tuning of the IF alignment or even a final resistive Q-dampening of x-former windings if finally deemed necessary.
:
:
:I have even worked with a receiver
:that was VERY well designed, RF decoupled and well laid out piece of military equipment, that incorporated 2 tuned front end RF stages and 3 I.F. stages...the BC 348, they pulled out all of the stops for that one.
:
:
:
:The other supplied data is within the fill in schematics red mark ups of your query about the functions of the different early stage audio tubes. Along, with their A B phase inverter relationships.
:
:
:The aspect of the set incorporating (two) 2 meg pots will have to be figured out by yourself after having a working unit in order to play with, and evaluate the controls.
:
:I can see three things..... if the two units are built as one dual pot unit, I can then see a loudness compensation circuitry being incorporated, with it being in circuit at low volume levels to perceive of enhanced bass response.(1)
:
:
:
:(1)
:(The Fletcher -Munson effect... where the human ear's response curve doesn't pick up low frequencies very well at low volume levels)
:
:
:
:The same situation could be true, if two separate pots might happen to be mechanically ganged together via coupled shafts, gearing or tandem coupled dial cord connected /drums.
:
:
:
:The third aspect being their utilization as two separate..... vernier volume / volume limit.... controls. The front panel decals might possibly clarify that aspect of utilization.
:
:
:
:SCHEMATIC MARKUP…….
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:73's de Edd
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