I have a Detrola 571X with the permeability style tuning, however the tube lineup is like the 571A/B. The caps, resistors, and tuning are just like the schematic for 571X but with tubes 12SA7, 12SK7GT, 12SQ7, 50L6GT, and 35Z5GT. I have recapped the radio, but get no stations. When I inject a signal with my signal generator at 455kc in the grid of 12SK7, I get the 400cycle tone all the way through the speaker even the volume is adjustable with the radio volume control. I get a very faint 400 cycle tone when I inject the signal to the plate of the 12SA7 tube. I get nothing when I try to inject before the plate of 12SA7.

Note the voltages of each tube that I have listed below. Why am I getting such high voltages on pins 5 and 6 of tube 12SA7? The resistors in this circuit check out about normal. What am I missing? As you can probably guess, this is only my second unit for restoring. What should I check next? I have replaced all the tubes with NOS tubes I purchased, but still get the same voltage readings. I do get a "live” hissing at full volume, which is just like any radio that is note tuned to a station. I believe all circuits after the 1st IF Can are operating properly, just touching the voltmeter probe to the grid of the 12SK7 gives a very faint reception of our strong local station when the radio is at full volume. Must be the probe acts as an antenna. If anyone can help, please respond, and also if you have or know of the correct schematic that would help also.

Required Voltages
Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6 Pin 7 Pin 8
12SA7 Osc/Mix 0 37.5AC 99 99 -4.2 0 24.5AC 0
12SK7 IF Amp 0 24.5AC 0 0 0 99 12.5AC 99
12SQ7 Det/1st Audio 0 0 0 0 0 16 12.5AC 0
50L6GT Power Output 0 85AC 91.5 99 0 0 37.5AC 5.9
35Z5GT Rectifier 0 117AC 112AC 0 112AC 0 85AC 112
Actual Voltages
Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6 Pin 7 Pin 8
12SA7 Osc/Mix 0 38AC 102.9 103 97.3 98.3 26AC 0
12SK7 IF Amp 0 26AC 0 0 0 103 13AC 102.9
12SQ7 Det/1st Audio 0 0 0 0 0 36 13AC 0
50L6GT Power Output 0 89AC 94.5 101.9 0 0 37.5AC 6
35Z5GT Rectifier 0 118AC 113AC 0 113AC 0 88AC 120

Hi Doug

A little hard to read but notice pin #5 on your 12SA7. Check the oscillator circuit. Coil continuity, component values, tube ok? etc. Your oscillator isn't operating. Pin #5 of 12SA7 should be several volts negative.

Norm

:I have a Detrola 571X with the permeability style tuning, however the tube lineup is like the 571A/B. The caps, resistors, and tuning are just like the schematic for 571X but with tubes 12SA7, 12SK7GT, 12SQ7, 50L6GT, and 35Z5GT. I have recapped the radio, but get no stations. When I inject a signal with my signal generator at 455kc in the grid of 12SK7, I get the 400cycle tone all the way through the speaker even the volume is adjustable with the radio volume control. I get a very faint 400 cycle tone when I inject the signal to the plate of the 12SA7 tube. I get nothing when I try to inject before the plate of 12SA7.
:
:Note the voltages of each tube that I have listed below. Why am I getting such high voltages on pins 5 and 6 of tube 12SA7? The resistors in this circuit check out about normal. What am I missing? As you can probably guess, this is only my second unit for restoring. What should I check next? I have replaced all the tubes with NOS tubes I purchased, but still get the same voltage readings. I do get a "live” hissing at full volume, which is just like any radio that is note tuned to a station. I believe all circuits after the 1st IF Can are operating properly, just touching the voltmeter probe to the grid of the 12SK7 gives a very faint reception of our strong local station when the radio is at full volume. Must be the probe acts as an antenna. If anyone can help, please respond, and also if you have or know of the correct schematic that would help also.
:
: Required Voltages
: Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6 Pin 7 Pin 8
:12SA7 Osc/Mix 0 37.5AC 99 99 -4.2 0 24.5AC 0
:12SK7 IF Amp 0 24.5AC 0 0 0 99 12.5AC 99
:12SQ7 Det/1st Audio 0 0 0 0 0 16 12.5AC 0
:50L6GT Power Output 0 85AC 91.5 99 0 0 37.5AC 5.9
:35Z5GT Rectifier 0 117AC 112AC 0 112AC 0 85AC 112
: Actual Voltages
: Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6 Pin 7 Pin 8
:12SA7 Osc/Mix 0 38AC 102.9 103 97.3 98.3 26AC 0
:12SK7 IF Amp 0 26AC 0 0 0 103 13AC 102.9
:12SQ7 Det/1st Audio 0 0 0 0 0 36 13AC 0
:50L6GT Power Output 0 89AC 94.5 101.9 0 0 37.5AC 6
:35Z5GT Rectifier 0 118AC 113AC 0 113AC 0 88AC 120
:
:

Thanks, Norm.

I agree with you about the voltage table being hard to read. I transferred a table over from MS Word, but it didn't come out very well. There are actually three areas where the voltages deviate from normal. Firat, pin 5 of 12SA7 should be -4.2 volts, I get +97.3. I also agree the oscilator is not working, but if it is just not working, should't the voltage be near zero instead of nearly all the way up to B+ voltage? Pin 6 of this tube is supposed to be near zero (Riders says 0) I get 98.3 volts positive. Again, where is the B+ getting into this tube. I replaced the tube with a NOS 12SA7GT and get the same results.

The only other voltage I get that is incorrect is pin 6 of the 12SQ7 tube. I get +36 instead of the +16 on the Riders diagram. I am just not used to the pereability tuning type front ends. All resistance appears to be correct, and the coils have continunity. Where else should I look? Thanks again.

:Hi Doug
:
: A little hard to read but notice pin #5 on your 12SA7. Check the oscillator circuit. Coil continuity, component values, tube ok? etc. Your oscillator isn't operating. Pin #5 of 12SA7 should be several volts negative.
:
:Norm
:
::I have a Detrola 571X with the permeability style tuning, however the tube lineup is like the 571A/B. The caps, resistors, and tuning are just like the schematic for 571X but with tubes 12SA7, 12SK7GT, 12SQ7, 50L6GT, and 35Z5GT. I have recapped the radio, but get no stations. When I inject a signal with my signal generator at 455kc in the grid of 12SK7, I get the 400cycle tone all the way through the speaker even the volume is adjustable with the radio volume control. I get a very faint 400 cycle tone when I inject the signal to the plate of the 12SA7 tube. I get nothing when I try to inject before the plate of 12SA7.
::
::Note the voltages of each tube that I have listed below. Why am I getting such high voltages on pins 5 and 6 of tube 12SA7? The resistors in this circuit check out about normal. What am I missing? As you can probably guess, this is only my second unit for restoring. What should I check next? I have replaced all the tubes with NOS tubes I purchased, but still get the same voltage readings. I do get a "live” hissing at full volume, which is just like any radio that is note tuned to a station. I believe all circuits after the 1st IF Can are operating properly, just touching the voltmeter probe to the grid of the 12SK7 gives a very faint reception of our strong local station when the radio is at full volume. Must be the probe acts as an antenna. If anyone can help, please respond, and also if you have or know of the correct schematic that would help also.
::
:: Required Voltages
:: Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6 Pin 7 Pin 8
::12SA7 Osc/Mix 0 37.5AC 99 99 -4.2 0 24.5AC 0
::12SK7 IF Amp 0 24.5AC 0 0 0 99 12.5AC 99
::12SQ7 Det/1st Audio 0 0 0 0 0 16 12.5AC 0
::50L6GT Power Output 0 85AC 91.5 99 0 0 37.5AC 5.9
::35Z5GT Rectifier 0 117AC 112AC 0 112AC 0 85AC 112
:: Actual Voltages
:: Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6 Pin 7 Pin 8
::12SA7 Osc/Mix 0 38AC 102.9 103 97.3 98.3 26AC 0
::12SK7 IF Amp 0 26AC 0 0 0 103 13AC 102.9
::12SQ7 Det/1st Audio 0 0 0 0 0 36 13AC 0
::50L6GT Power Output 0 89AC 94.5 101.9 0 0 37.5AC 6
::35Z5GT Rectifier 0 118AC 113AC 0 113AC 0 88AC 120
::
::

:WOW do I feel stupid. I rechecked the Oscilator coil and found it bad. I used jumper wires to test a spare Osc. coil, and the radio works fine!! At least I learned something. The voltage now reads -3.8 volts on pin 5 of 12SA7 when I have the spare Osc. coil hooked up with jumper wires. Now all i need to do is hard wire it in.

Thanks Norm.