I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,

I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.

:I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
:
:I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.

Hi Herman,

Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.

Radiodoc

In addition, those condensers, as shown in the schematic on this web site, supress signal straying that might otherwise occur through the batteries. This may not happen with a battery eliminator, depending upon design, but it can happen with batteries. A battery can hold a lot of juice for a long time, but, depending upon design, can fluctuate in available voltage with load fluctuation, due to high resistance design. In this way it cannot act like a filter condenser. Audio fluctuations in one stage set up load fluctuations on the battery. This affects the battery's voltage output to the other stages (in this case audio stages). Since the fluctuations in the battery are essentially those imposed upon it by one of the stages, the voltages fluctuate at audio frequencies, which are imposed on other stages--audio frequencies transfer from one stage to another. This makes perfect sense to me, but I don't know if I can explain it properly. I lack that gift. Anyway, this causes feedback--audio from one stage is transferred to a previous one, which is sent via normal path to the next one, and then through the battery back to the previous one...over and over again--causing a howl.

....So those condensers are necessary. A condenser of the right size can hold quite a strong, though momentary, charge, which can aid in supressing quick (audio or radio frequency) variations in battery voltage. If the originals are bad (leaky...they probably aren't electrolytic, so they probably won't dry up, but they can get leaky), you can increase the values if you wish. Using 10 or 20 MFD units will work fine, though the original values seem to suffice. Larger values certainly are not necessary, but provide extra filtering and stability, especially when you're pumping out mega bass from that '12A.

All that Radiodoc suggested is equally important. Check lead dress, as he said...placing the grid wires of one stage too close to the plate wires of another will cause feedback.

Thomas

:In addition, those condensers, as shown in the schematic on this web site, supress signal straying that might otherwise occur through the batteries. This may not happen with a battery eliminator, depending upon design, but it can happen with batteries. A battery can hold a lot of juice for a long time, but, depending upon design, can fluctuate in available voltage with load fluctuation, due to high resistance design. In this way it cannot act like a filter condenser. Audio fluctuations in one stage set up load fluctuations on the battery. This affects the battery's voltage output to the other stages (in this case audio stages). Since the fluctuations in the battery are essentially those imposed upon it by one of the stages, the voltages fluctuate at audio frequencies, which are imposed on other stages--audio frequencies transfer from one stage to another. This makes perfect sense to me, but I don't know if I can explain it properly. I lack that gift. Anyway, this causes feedback--audio from one stage is transferred to a previous one, which is sent via normal path to the next one, and then through the battery back to the previous one...over and over again--causing a howl.
:
:....So those condensers are necessary. A condenser of the right size can hold quite a strong, though momentary, charge, which can aid in supressing quick (audio or radio frequency) variations in battery voltage. If the originals are bad (leaky...they probably aren't electrolytic, so they probably won't dry up, but they can get leaky), you can increase the values if you wish. Using 10 or 20 MFD units will work fine, though the original values seem to suffice. Larger values certainly are not necessary, but provide extra filtering and stability, especially when you're pumping out mega bass from that '12A.
:
:All that Radiodoc suggested is equally important. Check lead dress, as he said...placing the grid wires of one stage too close to the plate wires of another will cause feedback.
:
:Thomas

Thanks, Tom. I'm using a battery eliminator. I will check the leads. I'm also using an O1A for final output. The original instruction sheet on the inside of the lid specify O1A's. Herman

'01As are simple triodes, and have relatively high internal capacitance between the grid and plate. This can promote oscillation, although I think it's more likely in the RF sections than the AF?

You might try shuffling the '01As around - some individual tubes may have different capacitance due to manufacturing tolerances or other factors.

:'01As are simple triodes, and have relatively high internal capacitance between the grid and plate. This can promote oscillation, although I think it's more likely in the RF sections than the AF?
:
:You might try shuffling the '01As around - some individual tubes may have different capacitance due to manufacturing tolerances or other factors.

Doug,

Herman in his original post mentioned he pulled all the tubes except for the two audio tubes and he still had the howl.

Radiodoc

Well, if rewiring the original condensers changes the howl to a motorboating sound, then perhaps the value should be increased. I don't know what kind of filtering you have available in your battery eliminator. Try using 20 MFD units from all B+ and C points to B-. Use units capable of withstanding 150 volts. When connecting from C- to B-, be sure that the negative end of the condenser faces C-. Connect a 50 MFD condenser from A+ to A-. All of these should eliminate feedback through the power wiring.

Again, check all lead dress and all components to be sure that there isn't some other error. Be sure that the primary and secondary of each transformer is connected to the appropriate tube. If, for some reason someone disconnected the wiring, and then you connected the primary of a transformer to the plate of one tube (and B+), and then accidently connected the secondary to the same tube instead of to the successive stage, you'd effectively create an oscillator. Check all wiring and be sure that it is perfect and well dressed. Then, if you cannot find any trouble (including open transformer windings), use the extra filter condensers as I suggested previously.

Thomas

::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
::
::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
:
:Hi Herman,
:
:Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
:
:Radiodoc

Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman

:::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
:::
:::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
::
::Hi Herman,
::
::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
::
::Radiodoc
:
:Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman

Herman,

I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.

Radiodoc

I think Doc may be on to something. Is there any reason you're not using a C- bias voltage? If your battery eliminator doesn't have a C voltage, maybe you can rig up a couple of dry cells in series?

If the grid is disconnected, the grid will become negative and cut off the tube's conduction. Sometimes, the negative charge will leak off somewhere, the grid then recharges - causing a putt-putt sound.

This may be a bit too technical at this point, but you can also put a resistor in series with B-. You'll have to select the resistance according to the load of your radio. The battery eliminator side of this resistor will be your negative voltage--choose the right resistor to give the right voltage (probably nothing more than 100 ohms at 1 or 2 watts). Connect a 30 MFD 25 WVDC condenser across the resistor for filtering and stability purposes. Connect your C- terminal to the eliminator side of the resistor.

Since C batteries last practically forever, you may simply go with them, but the resistor and condenser would eliminate the need for a battery holder or just the batteries themselves taking up space.

Thomas

:This may be a bit too technical at this point, but you can also put a resistor in series with B-. You'll have to select the resistance according to the load of your radio. The battery eliminator side of this resistor will be your negative voltage--choose the right resistor to give the right voltage (probably nothing more than 100 ohms at 1 or 2 watts). Connect a 30 MFD 25 WVDC condenser across the resistor for filtering and stability purposes. Connect your C- terminal to the eliminator side of the resistor.
:
:Since C batteries last practically forever, you may simply go with them, but the resistor and condenser would eliminate the need for a battery holder or just the batteries themselves taking up space.
:
:Thomas

Tom, C batteries are a possibility. I have an adjustable C supply on my battery eliminator. The darn thing was made to run without them, however. I moved on to probably the final output stage now after getting rid of the howl in the speaker. See my comments to Radiodoc. Herman

::::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
::::
::::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
:::
:::Hi Herman,
:::
:::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
:::
:::Radiodoc
::
::Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman
:
:Herman,
:
:I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.
:
:Radiodoc
:

:::::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
:::::
:::::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
::::
::::Hi Herman,
::::
::::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
::::
::::Radiodoc
:::
:::Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman
::
::Herman,
::
::I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.
::
::Radiodoc

Well you got the laugh on me with the lead switch on the transformer. The dummy who recently installed the transformers didn't know how to solder again. I have to teach him that foreplay is important to heat up the parts. I resoldered the loose lead and my howl is gone completely. I never heard such silence out of a speaker. With antenna and ground zip, touching everything I could think of zip. My radio has an earphone jack, I believe after the first AF tube. I plugged the Murdock 56's in and got some sound, not much though. But enough so it woud be coming through the speaker if the final AF stage were working.

Now, to the C voltage. There are no terminals and were none for a C battery. This was supposed to be some kind of a Charlie Freshman coup. My other Masterpiece uses C voltage according to the Riders schematic on this forum and in reality. There must be at least one more schematic floating around somewhere. I'm not giving up on this sucker yet.

Mr. Gump had a motto for my repair skills, "Stupid is as stupid does."

Herman
::

::::::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
::::::
::::::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
:::::
:::::Hi Herman,
:::::
:::::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
:::::
:::::Radiodoc
::::
::::Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman
:::
:::Herman,
:::
:::I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.
:::
:::Radiodoc
:
:Well you got the laugh on me with the lead switch on the transformer. The dummy who recently installed the transformers didn't know how to solder again. I have to teach him that foreplay is important to heat up the parts. I resoldered the loose lead and my howl is gone completely. I never heard such silence out of a speaker. With antenna and ground zip, touching everything I could think of zip. My radio has an earphone jack, I believe after the first AF tube. I plugged the Murdock 56's in and got some sound, not much though. But enough so it woud be coming through the speaker if the final AF stage were working.
:
:Now, to the C voltage. There are no terminals and were none for a C battery. This was supposed to be some kind of a Charlie Freshman coup. My other Masterpiece uses C voltage according to the Riders schematic on this forum and in reality. There must be at least one more schematic floating around somewhere. I'm not giving up on this sucker yet.
:
:Mr. Gump had a motto for my repair skills, "Stupid is as stupid does."
:
:Herman
:::

Hi Herman,

Don't beat yourself up about the bad solder joint. Everyone who has worked in electronics have had bad solder joints sometime or another. I'm not familiar with your headphones, however, I would think the output from the jack would be high impedance, say 2000 ohms or so. I would check that the new transformers are not hooked up backwards. Couldn't hurt to recheck voltages on the tubes either.

Radiodoc

::::::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
::::::
::::::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
:::::
:::::Hi Herman,
:::::
:::::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
:::::
:::::Radiodoc
::::
::::Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman
:::
:::Herman,
:::
:::I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.
:::
:::Radiodoc
:
:Well you got the laugh on me with the lead switch on the transformer. The dummy who recently installed the transformers didn't know how to solder again. I have to teach him that foreplay is important to heat up the parts. I resoldered the loose lead and my howl is gone completely. I never heard such silence out of a speaker. With antenna and ground zip, touching everything I could think of zip. My radio has an earphone jack, I believe after the first AF tube. I plugged the Murdock 56's in and got some sound, not much though. But enough so it woud be coming through the speaker if the final AF stage were working.
:
:Now, to the C voltage. There are no terminals and were none for a C battery. This was supposed to be some kind of a Charlie Freshman coup. My other Masterpiece uses C voltage according to the Riders schematic on this forum and in reality. There must be at least one more schematic floating around somewhere. I'm not giving up on this sucker yet.
:
:Mr. Gump had a motto for my repair skills, "Stupid is as stupid does."
:
:Herman
:::

Greetings! The earliest production examples of the masterpiece did not make use of a C battery.

What is the plate current of the 2nd AF 01A? if you do have plate current, do you hear any signal when touching the grid of the output tube with your finger? if not, the gink who replaced the second AF trnasformer may have used an output transformer, rather than an interstage unit. (I have seen this more than once!)The low impedence of the secondary would in effect have shorted the grid to the filament, and the tube would not amplify at all, just act as rectifier. A 201-A should always be slightly microphionic, if the grid is neither grounded nor connected to the plate. Perhaps you could try substituting another interstage transformer?

:::::::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
:::::::
:::::::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
::::::
::::::Hi Herman,
::::::
::::::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
::::::
::::::Radiodoc
:::::
:::::Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman
::::
::::Herman,
::::
::::I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.
::::
::::Radiodoc
::
::Well you got the laugh on me with the lead switch on the transformer. The dummy who recently installed the transformers didn't know how to solder again. I have to teach him that foreplay is important to heat up the parts. I resoldered the loose lead and my howl is gone completely. I never heard such silence out of a speaker. With antenna and ground zip, touching everything I could think of zip. My radio has an earphone jack, I believe after the first AF tube. I plugged the Murdock 56's in and got some sound, not much though. But enough so it woud be coming through the speaker if the final AF stage were working.
::
::Now, to the C voltage. There are no terminals and were none for a C battery. This was supposed to be some kind of a Charlie Freshman coup. My other Masterpiece uses C voltage according to the Riders schematic on this forum and in reality. There must be at least one more schematic floating around somewhere. I'm not giving up on this sucker yet.
::
::Mr. Gump had a motto for my repair skills, "Stupid is as stupid does."
::
::Herman
::::
:
:Greetings! The earliest production examples of the masterpiece did not make use of a C battery.
:
:What is the plate current of the 2nd AF 01A? if you do have plate current, do you hear any signal when touching the grid of the output tube with your finger? if not, the gink who replaced the second AF trnasformer may have used an output transformer, rather than an interstage unit. (I have seen this more than once!)The low impedence of the secondary would in effect have shorted the grid to the filament, and the tube would not amplify at all, just act as rectifier. A 201-A should always be slightly microphionic, if the grid is neither grounded nor connected to the plate. Perhaps you could try substituting another interstage transformer?

Bob, I'm the gink who replaced both. I'll try to measure plate current on second AF tube in the morning. They're both new tranformers from AES. I straightened some wires out today and I get a good screech touching the grid leak resistor using my earphones, but not much out of the speaker. Herman

::::::::I'm gradually learning this stuff. Someone offered the manual with a schematic, but I can't download it-maybe my Adobe is not up to date, but that's another problem for another day. Someone has a chassis up on the Bay just like mine, almost. It has a cap mine doesn't and I can't see where it goes on the standard schematic. It's vertical right above the second audio tube on the far left of the board bottom shown,
::::::::
::::::::I pulled tubes to get me at least in the right ball park. All it needs to howl nicely are the two audio tubes with all else pulled. Without a correct schematic, I was winging it with a few broken wires when I put the new audio interstage transformers in, but I think I hooked them up ok. If I knew where my missing cap connected, I could at least try some replacements. Any ideas? Thanks, again.
:::::::
:::::::Hi Herman,
:::::::
:::::::Be sure to keep the leads of the transformer primary plate leads as far as possible from the secondary grid leads. My schematic shows a couple of 1 MFD caps, one from the B+ 90 volts and B+ 45 volts to -B+A point. May want to check them if you haven't already. Just for laughs might try reversing the plate and B+ leads of the transformer between the audio tubes.
:::::::
:::::::Radiodoc
::::::
::::::Thanks. I tried the 1 MFD caps already. There was no hint they were ever installed on this version. With both in the circuit, I got "motorboating". I'll try reversing the leads on the transformer as you suggest. Who's going to laugh if it works? We'll see later as I had to clear the dining room table off so my wife has her work station when she gets home from one of her jobs soon. This version uses 45V on detector and 90V on final audio amp. tube and no C voltage. Herman
:::::
:::::Herman,
:::::
:::::I am using the schematic on this site. You mentioned that your radio used a 01A for output and C voltage is not used. Is the -C terminal connected to some other point or is itleft open? On this site schematic, it shows the -C terminal going to the secondary of the interstage transformer and on to the grid of the output tube. If -C is not connected anywhere (maybe to Gnd or +C-A) then the grid circuit of the output tube will not have a return and can cause motorboating.
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:::::Radiodoc
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:::Well you got the laugh on me with the lead switch on the transformer. The dummy who recently installed the transformers didn't know how to solder again. I have to teach him that foreplay is important to heat up the parts. I resoldered the loose lead and my howl is gone completely. I never heard such silence out of a speaker. With antenna and ground zip, touching everything I could think of zip. My radio has an earphone jack, I believe after the first AF tube. I plugged the Murdock 56's in and got some sound, not much though. But enough so it woud be coming through the speaker if the final AF stage were working.
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:::Now, to the C voltage. There are no terminals and were none for a C battery. This was supposed to be some kind of a Charlie Freshman coup. My other Masterpiece uses C voltage according to the Riders schematic on this forum and in reality. There must be at least one more schematic floating around somewhere. I'm not giving up on this sucker yet.
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:::Mr. Gump had a motto for my repair skills, "Stupid is as stupid does."
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:::Herman
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::Greetings! The earliest production examples of the masterpiece did not make use of a C battery.
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::What is the plate current of the 2nd AF 01A? if you do have plate current, do you hear any signal when touching the grid of the output tube with your finger? if not, the gink who replaced the second AF trnasformer may have used an output transformer, rather than an interstage unit. (I have seen this more than once!)The low impedence of the secondary would in effect have shorted the grid to the filament, and the tube would not amplify at all, just act as rectifier. A 201-A should always be slightly microphionic, if the grid is neither grounded nor connected to the plate. Perhaps you could try substituting another interstage transformer?
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:Bob, I'm the gink who replaced both. I'll try to measure plate current on second AF tube in the morning. They're both new tranformers from AES. I straightened some wires out today and I get a good screech touching the grid leak resistor using my earphones, but not much out of the speaker. Herman

YO! Herman,

Did you get your Masterpiece going?

Radiodoc