Phun with a 57 - Printable Version
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Phun with a 57 - BrendaAnnD - 04-18-2013
Just got one of these today, good solid cabinet and chassis.
First thing I found was that there was no B+ beyond the 80 socket. Most strange.
I found that there was no connection between the 80 and the field coil. I put a jumper in and the radio came to life... well, at least the audio did. It took some doing, but I finally got the IF tuned.
The RF section is another matter entirely. After going nearly crazy, I have gotten that working on the very low part of the band. The LO stops around 740 KHz. Pretty good reception on the one station I get (603 KHz). As powerful as that station is, it's quite difficult generally to receive it without a lot of noise on any radio without a loop antenna, but on this one, it's quite nice and clear. But, as I said, it's dead as a mackeral on most of the dial.
I guess first thing I should try is to replace the 77 and see if it works any better. This is only a 4 tube regen-superhet, so it's not a hot set, and the capacitor count very low, some of which seem to have already been replaced with modern caps.
RE: Phun with a 57 - Mondial - 04-18-2013
Yes, I would try changing the 77 mixer/osc tube first. The autodyne converter is sometimes finicky as to tubes. The other thing you might check is the 77's cathode resistor (#8 on schematic) which should be 8K. If this resistor has drifted up in value, it can cause intermittent oscillation, especially at the higher freqs.
RE: Phun with a 57 - Ron Ramirez - 04-18-2013
Are the antenna and oscillator coils OK? More often than not, they are bad. It's (almost) always the outer winding that goes bad.
RE: Phun with a 57 - Radioroslyn - 04-18-2013
I'm with Ron on this one. Bet your osc coil is marginal just being able to offer enough feedback to cause the osc to run at the low end of the band.
I picked up a 54 awhile back. Boy what a pain to work on. Parts are really crammed in in that set.
GL
Terry
RE: Phun with a 57 - BrendaAnnD - 04-19-2013
Well.. here's the news:
The oscillator and antenna coils are fine.
I don't have any spare 77's, so I just swapped the two tubes in the radio to the other sockets (detector isn't quite so critical), and was totally surprised that when I turned the set back on, it was alive with stations. It's not too bad, about par for one of these type radios, favorably comparable to the little 4 tube metal cased autodyne sets from the 40's. I'm a happy camper.
