50-925 no FM - Printable Version
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+--- Thread: 50-925 no FM (/showthread.php?tid=12254)
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50-925 no FM - Eric Adams - 05-12-2015
Hi guys,
I've run into a wall with this radio. All caps have been replaced. All resistors, coils and tubes have been tested and replaced as nec. I am able to do a complete alignment, but I have no FM reception at all
, not even static. AM works great!What do you think?
Thanks,
RE: 50-925 no FM - Ron Ramirez - 05-12-2015
Hmmm...
Can you try injecting an FM IF signal along the FM IF path and see where it appears (or disappears)?
RE: 50-925 no FM - Eric Adams - 05-12-2015
Sounds good. I'll check it out and get back to you.
Thanks, Ron.
RE: 50-925 no FM - Radioroslyn - 05-12-2015
I have no FM reception at all [Image: http://philcoradio.com/phorum/images/smilies/icon_eek.gif] , not even static.
Funny thing about that's how FM works No Static!!!
Your a glutton for punishment!!!
If you don't a Fm generator you can use an am signal
but use a tracer with a RF probe (diode detector) to follow
the signal around till you get to the limiter stage.
GL
Terry
RE: 50-925 no FM - Eric Adams - 05-12-2015
OK, it appears that the signal goes in to the 1st IF trans and doesn't come out. It feels like the core is binding when I try turn it. Could the trans be bad? BTW, I have an exact replacement.
Thanks,
RE: 50-925 no FM - Radioroslyn - 05-12-2015
Possible but I'd measure the resistance across TC-6 Should have a very low resistance. I have had cores seize to the coil form and while trying to adj it has ripped the wires right off the coil render it useless.
Terry
RE: 50-925 no FM - Eric Adams - 05-12-2015
The resistance was very low and matched with the spare that I have. Any other ideas?
RE: 50-925 no FM - Radioroslyn - 05-12-2015
(05-12-2015, 06:29 PM)Eric Adams Wrote: The resistance was very low and matched with the spare that I have. Any other ideas?
Well I think I'd just swap it out. Could have a bad cap across the winding. Only 4 wires not a big deal.
Terry
RE: 50-925 no FM - Eric Adams - 05-12-2015
Thanks. I'll give it a shot.
RE: 50-925 no FM - Eric Adams - 05-19-2015
OK, I replaced both 1st and 2nd IF transformers
No luck.Any other ideas?
RE: 50-925 no FM - Radioroslyn - 05-19-2015
Soooo where are you losing signal now?? Is it making it though the 2nd IF stage??
Terry
RE: 50-925 no FM - Eric Adams - 05-19-2015
I was too frustrated to check. I'll check it tomorrow and let you know.
RE: 50-925 no FM - Radioroslyn - 05-19-2015
I find FM stuff frustrating too!!!
Terry
RE: 50-925 no FM - mikethedruid - 05-20-2015
Keep on plugging at it. You have my sincere sympathy; I restored a 48-482. Double and triple check all your connections. You'd be surprised how easy it is to look at something and see it as right one time, only to pick it up on a second look closely following the diagrams that show parts locations and wiring, and the schematic. Don't get frustrated. One thing about these old radios, when they don't work, something IS wrong. You'll find it eventually.
RE: 50-925 no FM - Eric Adams - 05-20-2015
Thanks mike. I know what you mean. I have restored two 48-482s and had less trouble. The set of schematics and pages of troubleshooting that is available for the 48-482 is fantastic and really helps with diagnosis. The 50-925 doesn't come close with their poor documentation.
I haven't given up yet but it is being punished for a while. It will sit on the shelf until I feel better about it.