magnavox fm-41 - Videokarma.org TV - Video

JGlenn · #1 10-30-2008, 09:34 PM

Hi,
I picked up a little magnavox fm-41 table radio the other night. The people I got it from tried to plug it in and claimed it worked but that wasnt the cade when I got it home. The tubes light up but there is no sound at all from the speaker. where should I start looking? It seems like a cool little radio so I would like to restore it. Its has all original tubes except for a radio shack 50c5 the rest of the tubes are: 12av6, 12al5, 2 12ab6, and 12be6. It had one loose lead on the speaker that a resoldered but still no sound at all which seems kindof odd I would of figured it would at least pick up static or hum.

Hemingray · #2 10-31-2008, 02:10 AM

I'm gonna suspect a dead speaker. I encountered the same problem with a General Television AA5 AM radio that I'd repaired. Best way to check this is to put another speaker across it, If you get sound then, then the speaker is a dud.

While you're in there, give the 50C5 a quick test. There has never been a time where I DON'T come across a 50C5/50L6 that has tested usable (on my tester, (Sencore TC142), they'll barely make it to 40 (good is 70+).) The only case of a good tube, would actually be the 50L6 on my General Television (more on that later. lol)

JGlenn · #3 10-31-2008, 02:58 PM

hey thanks for the reply, I did suspect the speaker too so i tried it with another speaker and had the same result. I checked the speaker in the radio with a aa battery and it clicked as it should so I guess I'll look into that 50c5. Is there a way to check it without a tube tester or should I just order a fresh one?

Hemingray · #4 10-31-2008, 04:01 PM

Do you have another radio that utilizes a 50C5? Any common AM only AA5 radio will help you here. At this stage I'll also begin to suspect the audio transformer.

radiotvnut · #5 10-31-2008, 04:21 PM

In this situation, I usually check the voltages at the audio output tube socket. This will usually reveal a problem in the power supply or audio stage. For starters, locate the primary winding of the audio output transformer. Check the voltage on both leads of the primary winding. You should have between 90 and 120 volts there. If there is no voltage on either lead, you have a power supply problem. If there is voltage on one lead but not the other, you have an open primary winding and a new output transformer is in order.

Hemingray · #6 10-31-2008, 07:33 PM

Quote:

Originally Posted by radiotvnut

In this situation, I usually check the voltages at the audio output tube socket. This will usually reveal a problem in the power supply or audio stage. For starters, locate the primary winding of the audio output transformer. Check the voltage on both leads of the primary winding. You should have between 90 and 120 volts there. If there is no voltage on either lead, you have a power supply problem. If there is voltage on one lead but not the other, you have an open primary winding and a new output transformer is in order.

Dang, never thought of that one. *doh*

JGlenn · #7 01-25-2009, 11:07 PM

I finally got this thng going, I think the main issue was just dirty and some loose tube sockets. The tuning dial is quite a bit off but it seems to pull in stations halfway decent. It plays drasticly louder on some stations than others so Im not sure If there are suspect weak tubes in a radio like this I should replace or probably just recap it first and see if anything changes. It is probably almost half a century old so Im sure those caps have about had it although it does sound pretty good for what it is once it warms up and no real hum either.

AUdubon5425 · #8 01-26-2009, 01:26 AM

Quote:

Originally Posted by JGlenn

It plays drasticly louder on some stations than others so Im not sure If there are suspect weak tubes in a radio like this I should replace or probably just recap it first and see if anything changes.

Recap it and check resistors in the AVC (automatic volume control) circuit.