I’m working on a GE A-53. I’ve recapped it and replaced 3 out of spec resistors. Here’s the problem. When I power it up, I get no sound. The speaker is O.K. I checked the voltages against the information with the schematic on this web site and here’s how they match.
All measurements are referenced to ground.
6A8 Converter. Cathode should be 3.2V. I have 7.3V. Screen grid should be 50V. I have 77V. Plate should be 275V. I have 241.8V.

6K7 IF Amp. Cathode should be 3.2V. I have 7.2V. Screen grid should be 50V. I have 76.4V. Plate should be 275V. I have 241.5V.

6J7 Det. Cathode should be 2.3V. I have 4.0V. Screen grid should be 50V. I have 76.3V. Plate should be ?? I have 209.7V.

6F6 Output. Cathode should be 18V. I have 10.8V. Screen grid should be 275V. I have 241.2V. Plate should be 260V. I have 3.8V.

Although all of the tubes tested good, could there be a problem with the output tube?

Help!!

The plate voltage on the output tube is too low. Your most likely suspect is the output transformer T2. Its' resistance should measure about 650 ohms. It may be open. Also check the capcitors C27 and C28 as either one may be shorted but you recapped the set so they should be fine. Check for any miswires that were done while recapping or by any previous repair attempts (technician tracks).
MRO

Thanks for the tip Mark. The output transformer had an open primary. It took a lot of self-convincing because I have a spare A-53 chassis and the output transformer on it has an open primary also. What are the odds? I wound up temporarily wiring in a transformer scavenged from an old amplifier I had lying around and vola! The radio now has sound.

However, before I mount and permanently wire in a substitute transformer, I need to know how to determine the electrical requirements for this set? The schematic only has the resistance values for the primary and secondary windings. When looking for a substitute what do I look for? Is this circuit hard on output transformers?

:The plate voltage on the output tube is too low. Your most likely suspect is the output transformer T2. Its' resistance should measure about 650 ohms. It may be open. Also check the capcitors C27 and C28 as either one may be shorted but you recapped the set so they should be fine. Check for any miswires that were done while recapping or by any previous repair attempts (technician tracks).
:MRO

Determining the proper replacement transformer is rather difficult without a cross reference. Sometimes DC impedances are given in the old schematics. Most modern transformers are listed by their AC impedance, however. For any given DC impedance, AC impedance can be totally different by changing turn count or iron design. Of course increasing turn count will also affect DC impedance...unless the gauge of the wire is also increased, which would tend to keep DC impedance the same if changed perportionally.

Sorry to get so technical, but this is the dilema we must face when replacing transformers. Just about any tube type transformer will do in your radio, as it's pretty flexible. To get optimum audio quality and strength, purchase a universal output transformer from www.tubesandmore.com, or radiodaze.com. It will have a tapped primary and secondary. Your speaker is most likely a 3.2 (or 3.5) ohm speaker, as this was common, but since it probably isn't marked, you'll have to try different taps. First connect the primary tap to the output tube plate that puts the appropriate voltage on the plate. Several may give a similar voltage. Then choose the secondary that yields the best and strongest tonal quality. Now do the same with the primary. Hopefully your plate voltage will remain the same for optimum output. It can increase, but this will load down the power supply more. You'll get more wattage, though.

Keep in mind that decreasing the primary's impedance will decrease bass response but increase wattage. Increasing impedance will decrease bass response but decrease wattage.

Thomas

Thanks for the info Thomas. I'll do some experimenting and see how it works out.

Leon: here are some suggestions,

Touch the center terminal of the volume control pot with a screw driver or your finger, and see if you get a hum. If so, the audio section is likely functioning.

Check the IF xfmr secondaries for continuity. (You've got B+ everywhere, so it seems that the primaries are OK.)

Put another radio next to the A53. Tune the other radio to a quiet point on the dial around 1360Hz. Then tune the A53 back and forth around 1360-460 = 900Hz. See if you can pick up the A53's oscillator whistle on the other radio.

:I’m working on a GE A-53. I’ve recapped it and replaced 3 out of spec resistors. Here’s the problem. When I power it up, I get no sound. The speaker is O.K. I checked the voltages against the information with the schematic on this web site and here’s how they match.
:All measurements are referenced to ground.
:6A8 Converter. Cathode should be 3.2V. I have 7.3V. Screen grid should be 50V. I have 77V. Plate should be 275V. I have 241.8V.
:
:6K7 IF Amp. Cathode should be 3.2V. I have 7.2V. Screen grid should be 50V. I have 76.4V. Plate should be 275V. I have 241.5V.
:
:6J7 Det. Cathode should be 2.3V. I have 4.0V. Screen grid should be 50V. I have 76.3V. Plate should be ?? I have 209.7V.
:
:6F6 Output. Cathode should be 18V. I have 10.8V. Screen grid should be 275V. I have 241.2V. Plate should be 260V. I have 3.8V.
:
:Although all of the tubes tested good, could there be a problem with the output tube?
:
:Help!!
: