Philco 20 voltages - Printable Version

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+--- Thread: Philco 20 voltages (/showthread.php?tid=22217)

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RE: Philco 20 voltages - Patrick - 03-01-2021

Thanks, Rob. I'll admit, I didn't pull the coils out of the cans to inspect them. I'll do that, and rewind in necessary.

Pat

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RE: Philco 20 voltages - Patrick - 03-14-2021

And now, the end of the story.

Voltages all close enough when measured from the right place. Bought a sheet of mica, split it to .001-.002 thickness and replaced all three variable cap trimmer insulators. Now I can adjust them all to between 300 and 700 picofarads (if I read my LCR meter correctly). But the biggest problem was the 71A tubes.

There was only low volume. When I pulled one of the 71A's, the volume doubled. I tried 5 different 71A's, and finally got the proper volume. All the tubes tested fairly high. But I guess they really make a difference in this radio.

All said and done, it was fun. And thanks for the help to all. Now I'm starting on another 20. This should be alot easier. At least re-stuffing the bakelite blocks takes less than 5 mintues each, now. Got one or two more 20's to follow.

Pat

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RE: Philco 20 voltages - morzh - 03-14-2021

Pat

I do not remember this problem with 20. I did not have to pick and match 71A. Not sure what your case is, but I would recheck each RF stage alignment. Yes it might in theory be dependent on 71A . Though not much.

Or if you are satisfied, then call it done.

Your two other 20s will tell you if your assumtion is correct.

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RE: Philco 20 voltages - Patrick - 03-15-2021

Thanks. I'm sure I will get more info with the others. Just in case, I'm keeping the weak 71As. and I'll try them in the others.

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