[cwirth]

I am restoring a 38-12. I have replaced all the caps and checked all the tubes. There is no audio at all. Would the output transformer located on top of the speaker be the problem? What is the best way to test the transformer? Anything else I should check?

Thanks.

[marty]

Hi All;
Partually, it depends on what you have for test equipment..
For starters, If you have an ohm meter, then free up one lead on each side of the coil and see if it shows any ohm readings.. For the moment it doesn't matter what the reading is, but that you have one.. If you find out from further test that there is still trouble, then the reading will make a difference..
Next, if you have an audio oscillator or a source of audio.. First check that the speaker works and ohm it out.. Then connect the speaker back to the Transformer back to the speaker.. Thru a capacitor pass an audio signal, You should get some level of sound, it may be barely audiable or quite loud.. The main thing is do you get any sound from it..
As another alternative, With the Cap you can use it to prod the filament 6.3 volt AC line for a source of 60 cycle hum, then go from the speaker back thru the transformer until you find where the signal disappears..
THANK YOU Marty

[Arran]

Let's see, if there is no audio at all, including no hum coming from the speaker, then there may be no B+ voltage going through the set. Find a schematic and check for the B+ voltage in various spots starting from the cathode/filament of the rectifier tube, the filed coil of the speaker, and the plate and screen of the power output tube.
Regards
Arran

[Groundhog74]

I did a 38-12 last year that had nothing, no noise whatsoever. I put a new oscillator coil (Antique Electronic Supply...part number P-C70-OSC) in it and it works great now. Just a thought. I ohmed out the coil and found it was open. Good luck.

[morzh]

I would start from what Arran said.

If you have no noise whatsoever, start checking what he listed. Major voltages, and then if needed - field coil and of course output transformer integrity. Those are low hanging fruits and are likely to be culprits.

Then you go to finer less obvious things if these check out but first things first.