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41-285 Don't Know What To Do Next - Printable Version

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Re: 41-285 Don't Know What To Do Next - Johnny - 04-20-2009

I slaved in the spare transformer and it made no difference. All wires in the original transformer have been replaced and the resistances on the coils are within spec. I'll have to go through those steps again in your next thread. I'm taking the band switch back out AGAIN. There's something funny in the switching on that thing. Band indicator lights are intermittent etc. It didn't start doing this until after I gave it a thorough cleaning. Something went awry in there. I'll get back to ya.

Thanks,
Johnny

Re: 41-285 Don't Know What To Do Next - Johnny - 04-20-2009

Raleigh! Oh Raleigh! All of the testing that has been done and all of the people that have been involved... You tell me to check continuity between pin 7 of the 1st IF 7B7 tube. Well there was no connection of any kind to pin 7 of this tube. Duh!!! Radio don't work without cathode grounded. She sings like a bird now. I can only say... THANK YOU VERY MUCH!!!

Johnny

Re: 41-285 Don't Know What To Do Next - Raleigh - 04-21-2009

Glad to be of help. It is great to hear that your 41-285 is working OK. Do you still have problems with the band switch? What is the cabinet like? My first Philco was a 41-280 that I still have. I bought it in working condition in 1982 but never dared to tear into it until a couple of years ago. I never would have if I hadn't gotten lots of help from the Internet, particularly this site and Phil's Old Radios that finally made me brave enough to try.

I think we were all misled by the fact that you picked up your strong local station when you connected your meter to the plate of the 1st IF. True, but a red herring. Once you verified that you couldn't get a tone with your signal generator on the 1st IF grid it was clear that normal servicing procedure was called for, not trying to diagnose the presence of that radio station. I think Norman Leal on the "other" forum called it correctly that you were just picking that signal up with your meter lead as antenna. What was so puzzling was that I wouldn't have thought the 1260 KHz signal would get through the 2nd IF stage since it is tuned to 455 KHz or that the 2nd detector would detect the audio from the 1260 KHz. I guess we all learned something!

I've been doing this a couple of years now. One of the first non-working sets I restored was a 40-150 that had been hacked by someone else. He cut out a bunch of wiring from around one of the IF tubes and hacked in a bunch of modern filter caps and left them and some other resistors and capacitors hanging in mid-air by some stiff wire, not connected to terminal strips. I had to cut out all that mess and figure out where the original wires and components went. When I had finished restuffing the original filter caps, recapping the wax caps, and replacing the rubber wires, I got nothing until I worked backwards from the speaker and realized that I'd left out the B+ wire to the plate of the IF tube. Once I figured out where that went, the radio finally worked. It is often a problem to pick up a restoration or repair where someone else left off. There is no good reference (that I've found) to tell you where all the original wires went.

I'm a big believer in the servicing techniques in "Elements of Radio Servicing." I recommend it all the time. You can get a .pdf copy of that book in six separate .pdf files at this site: http://antiqueradios.com/archive.shtml . It is really easy to follow. I read the whole book before I ever tore into a radio, and I refer back to it all the time.

I've gotten lots of help from this site over the last couple of years. Ain't the Internet great?

Re: 41-285 Don't Know What To Do Next - Johnny - 04-21-2009

Hi Raleigh,

The band switch did have a really messed up contact. It was wafer "C" contact #9. All bent up and not making contact. I was able to repair it. Also after I cleaned it the first time I guess I cleaned out everything that was helping the contacts make their connection for the dial lights. They were intermittent after I put it back together. I was able to tighten these up and all of that works well now.

I have the "Elements of Radio Servicing" now and yes, that looks like it will be a big help. Thanks!

And thanks again for the help with this set.

Johnny