1959 Radio schematic

[John Kogel]

This was state of the art for an inexpensive table radio in 1959. AM and FM travel along the same path from the antenna to the rotary switch, where you select one or the other frequency to listen to. The Zenith C845 has an 8" speaker and a little tweeter and played well until something went south during the restoration process. I have replaced most of the waxed paper capacitors and have lost FM.

Nostalgia Air is an online forum that operates on a shoestring, actually it dangles from the thinnest tungsten filament, can't post pics there, so with your indulgence, i am posting the schemo here, while seeking help there, thanks.

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[Marc]

AM/FM switch went bad?

Marc

[Steven Hockstein]

Nice!

When I was a kid my dad had a Heathkit stereo system that he had built.

Those were the days that a handy person could fix a piece of electronics equipment or the car. Now you just throw away or junk them because the cost of replacing is not much different than repairing.

[Les]

Three or four times a year my Father would take a few tubes out of the TV and send me on my bike over to the Western Auto store and test them. if one was "bad" I would bring a replacement back and we would be in business again!

[John Kogel]

There are 8 tubes, all labeled 'Zenith' so likely all originals. AM plays strong so those tubes are still good. The green square gizmo is a selenium rectifier which replaces one tube.

Marc, I checked the switch and cleaned it again. I get crackle and hum but no rock and roll. I think the FM oscillator is refusing to oscilliate.

Weird one. I took the chassis out and pulled the shields off of 2 tubes in the front end, the AFC and the converter. I'm going to check for loose or dirty contacts. FM comes back loud and clear. Put shield back on, FM cuts out. I asked the experts and the consensus was, you don't need to fix it if it plays good that way. []

[Marc]

There are 8 tubes, all labeled 'Zenith' so likely all originals. AM plays strong so those tubes are still good. The green square gizmo is a selenium rectifier which replaces one tube.

Marc, I checked the switch and cleaned it again. I get crackle and hum but no rock and roll. I think the FM oscillator is refusing to oscilliate.

Weird one. I took the chassis out and pulled the shields off of 2 tubes in the front end, the AFC and the converter. I'm going to check for loose or dirty contacts. FM comes back loud and clear. Put shield back on, FM cuts out. I asked the experts and the consensus was, you don't need to fix it if it plays good that way. []

Ground that shield and try again. Got to be a solid, preferably soldered, ground. IF frequencies are strange animals.

Marc

[John Kogel]

There are 8 tubes, all labeled 'Zenith' so likely all originals. AM plays strong so those tubes are still good. The green square gizmo is a selenium rectifier which replaces one tube.

Marc, I checked the switch and cleaned it again. I get crackle and hum but no rock and roll. I think the FM oscillator is refusing to oscilliate.

Weird one. I took the chassis out and pulled the shields off of 2 tubes in the front end, the AFC and the converter. I'm going to check for loose or dirty contacts. FM comes back loud and clear. Put shield back on, FM cuts out. I asked the experts and the consensus was, you don't need to fix it if it plays good that way. []

Ground that shield and try again. Got to be a solid, preferably soldered, ground. IF frequencies are strange animals.

Marc

Hi Marc. These are cardboard sleeves with a metallic silver paint. Engineer said Shields, Beancounter said use these. I haven't mastered soldering on painted cardboard.

The shields make contact with the chassis, but not that well.

'Further evaluation is required.' []