Interested in anyone's thoughts on this one: I can trace a received signal thru the radio, but only hear a little audio from the speaker. And it's distorted. Pulled one of the 42's in PP from socket "A"...no change. Put it back in and pulled the tube in socket "B"....audio goes away. Swapped tubes and got the same result. That is, it doesn't seem to matter which tube is in which socket, socket "B" seems to be the only one delivering audio. It's been re-capped and any out of spec resistors replaced. Transformer? How does one tell? Oh, yes, and there is a little bit of crackling from the speaker for a short duration every time I power it up. Thanks for your ideas.
Jim

Check the primary of the output transformer, it may be open.
73
Bob Kulow

Bob,
Yup, one side of primary to CT is 375 ohms. The other side of primary to CT is way up there, essentially open. Figured it had to be the transformer, but wanted to get another opinion before I did another thing to this beast. This is one of those where it feels like it's me vs the radio, and the radio is winning half the time. Ok, time for a transformer, then it's on to the sometimes functioning oscillator!
73 & TNX
Jim

Hi,
for the sometime functioning oscillator, first look for cold solder joints, or corroded tube pin contacts. If those do not correct the problem, look at the paper cap(s) for the oscilaltor section, as one may be partly pulled apart form time, or blown through (if you get a long drawn crackling sound- this is the latter of the two conditions). You can sometimes locate the offender by moving the leads slightly while it is operating.

:Bob,
:Yup, one side of primary to CT is 375 ohms. The other side of primary to CT is way up there, essentially open. Figured it had to be the transformer, but wanted to get another opinion before I did another thing to this beast. This is one of those where it feels like it's me vs the radio, and the radio is winning half the time. Ok, time for a transformer, then it's on to the sometimes functioning oscillator!
:73 & TNX
:Jim

Hello John! Thanks for the tips..will give them a try. Still have to get the output transformer installed. Found one yesterday, but with no secondary CT for the tone control. Going to use it anyway. It's been suggested to me that I can just hook that tone wire to the top of the secondary (which doesn't show on the schematics, by the way), maybe thru a resistor...or just leave it out. I guess it's a low volume bass boost. What do you think?
jim

Hi,
The tone control, normally would tie in to the plate of the output tube, but that is not the only point where you can tie in.

Philco did tie the tone control to one tube of a "push pull" pair, as can be seen in the 37-640. The do add a fairly high value resistor to keep from affecting the balance between the tubes, but it is how they did it.

:Hello John! Thanks for the tips..will give them a try. Still have to get the output transformer installed. Found one yesterday, but with no secondary CT for the tone control. Going to use it anyway. It's been suggested to me that I can just hook that tone wire to the top of the secondary (which doesn't show on the schematics, by the way), maybe thru a resistor...or just leave it out. I guess it's a low volume bass boost. What do you think?
:jim