Emerson 659B: No FM Reception - Videokarma.org TV - Video

YamahaFreak · #1 03-03-2008, 10:22 PM

I got this nice early AM/FM set at a small local swap meet. It's from 1949 I think, and the earliest set with the FM band I've seen. The AM works great, but there's absolutely no response on the FM side. Most of the tubes tested bad, so I'll replace them to see if it makes a difference. The radio displays quite well, and I was told it was reworked and recapped as well. Anyone know the solution to my FM not being there? Someone suggested replacing the 19T8 tube (part of the FM section).

radiotvnut · #2 03-03-2008, 11:51 PM

I'd replace any tubes in the FM circuit. I've actually seen them test good in a tube tester but would not function in the circuit. Otherwise, you'll have to get a schematic and a multimeter and make some voltage checks. If this set does not have a power transformer, it will probably be a hot chassis. It would be best to plug the chassis into an isolation transformer. Otherwise, use extreme caution or you could recieve a possible lethal shock.

YamahaFreak · #3 03-04-2008, 05:03 AM

Quote:

Originally Posted by radiotvnut

I'd replace any tubes in the FM circuit. I've actually seen them test good in a tube tester but would not function in the circuit. Otherwise, you'll have to get a schematic and a multimeter and make some voltage checks. If this set does not have a power transformer, it will probably be a hot chassis. It would be best to plug the chassis into an isolation transformer. Otherwise, use extreme caution or you could recieve a possible lethal shock.

I am assuming that this is a hot-chassis radio, as there is no transformer. If it helps, the tube complement is as follows:

1x 6BH6
3x 6BJ6
1x 12AT7
1x 12BE6
1x 19T8
1x 50L6GT

I considered simply reversing the power plug in the outlet, but something tells me that won't do anything at all.

Pic of the radio soon.

Unlike both other 659B's I've ever seen, this one is cream/whitish, rather than dark brown. Bakelite, I think?

Tom Bavis · #4 03-04-2008, 08:08 AM

I'd suspect the 12AT7 first - it's the oscillator / mixer for FM. Yes, it is a hot-chassis radio.

Find a similar schematic (1951 - 659B) here: http://techpreservation.dyndns.org/s...n_659B_31.djvu - you'll need the djVu plug-in from lizardtech.com

YamahaFreak · #5 03-04-2008, 10:21 PM

I replaced all tubes except the 50L6 and 12BE6 (they tested great) and now the FM is back! Yay!

I've got a 60-cycle hum on both bands, though. (It was always there, I just didn't mention it earlier.) As a result, the music is distorted, even at low volumes. I believe the word is 'motorboating'.

The radio was indeed recapped, but not very well. I jiggled some of the caps around and spaced them apart from one another, and that seemed to reduce the hum somewhat. If I wanted to send my radio to someone here to have it correctly recapped, who would be best?

Pic of radio:

radiotvnut · #6 03-04-2008, 10:31 PM

I fixed a dead radio once that someone recapped but the soldering wasn't worth a flip. After I resoldered everything, it worked fine. What value electrolytics are in there? It's quite possible that someone put the wrong value caps in place of the original.

BTW, I've got a red AM only version of this radio.

YamahaFreak · #7 03-05-2008, 12:00 AM

Quote:

Originally Posted by radiotvnut

I fixed a dead radio once that someone recapped but the soldering wasn't worth a flip. After I resoldered everything, it worked fine. What value electrolytics are in there? It's quite possible that someone put the wrong value caps in place of the original.

BTW, I've got a red AM only version of this radio.

There's a mixture of 'lytics bundled together, disc caps, and what look like Orange Drops. Oh, and a crapload of electrical tape.

I believe the electrolytic caps were bundled together to replace the original value of a larger paper or wax cap. What's the model # of that AM-only model, and what tubes has it got?

Sounds neat!

Old1625 · #8 03-05-2008, 07:43 AM

I had an Emerson like that one, only brown instead of cream colored. It had notable bass response for its being a table radio.

As for your electrolytic pi network you need to be sure the negative leads are returned exactly where the originals were--not merely returned where it fits conveniently. Also check the state of the capacitor sometimes found in old "hot chassis" radios that connects the common negative line to the chassis. If it is the original it can cause problems--including possibly going off with a loud pop and foil confetti everywhere.

YamahaFreak · #9 03-05-2008, 07:37 PM

Quote:

Originally Posted by Old1625

I had an Emerson like that one, only brown instead of cream colored. It had notable bass response for its being a table radio.

As for your electrolytic pi network you need to be sure the negative leads are returned exactly where the originals were--not merely returned where it fits conveniently. Also check the state of the capacitor sometimes found in old "hot chassis" radios that connects the common negative line to the chassis. If it is the original it can cause problems--including possibly going off with a loud pop and foil confetti everywhere.

There are very few, if any, original caps now. When you say 'original position', do you mean the actual physical location of the wire? That may be indiscernible by now.