[dtvmcdonald]

I've been working on my Marconi 702 TV. This set is not "restored" per se.
It was "repaired" when I got it. It had a nice new EHT transformer and
EHT filter caps that tested perfect. I replaced all the flaky looking
electrolytics and a couple of early film caps with my usual stock of
Panasonics and Nichicons. One problem is that many old wax caps
are still in place, though all the ones I could get at were already
disconnected and early film ones used.

I realigned the TRF with my new sweep generator. It has a problem in
that the third stage can't be tuned due to a stuck core. However, it was close
and I have it in a state producing an excellent video waveform.

The speaker was bad. I am loathe to remove the audio chassis since
it (apparently) requires removing the picture tube. So I replaced the
speaker with a modern one just stuffed in place. It works fine with enough signal.
But enough signal means that the audio bothers the sync.

I measure about 5 mV p-p at 41.5 MHz at the grid cap of the X 41 frequency
changer (with the audio carrier at a level that does not bother the sync, and
produces weak audio). I get a few volts signal at 1.5 MHz on the plate cap
of the IF amplifier. The audio tuner tunes correctly.

The AC voltage on the volume control is less than one volt. This produces weak sound.

Do these voltages seem correct?

Oh yes, did I mention that the audio output tube is soldered in place.

Does anybody have any suggestions of what to try without removing the audio
chassis? OR, can the audio chassis actually be removed, safely,
without removing the picture tube?

I cannot test the removable audio tubes as I don't have the test data.
Are there American equivalents as could use as test templates?

These are 4 volt tubes ... is that right?

If I can't fix it I think I will simply add a tiny solid state amp I have
between the speaker output and the speakers.

Doug McDonald