Working on a zenith 10-s-669 but I'm having some problems. I recapped the radio and replaced some of the rotted wires but when I turn it on there is no sound. No static or stations. Just a slight electric hum from the speaker. Sometimes it motorboats when tuned to around 150. Anyone know what might be the problem or how to find out? Is it an oscillator, is the tuner too oxidized? All the tubes light up and get warm. Could it still be a weak tube? Someone help me out here, I'm new to this and kinda flustered
>>984322
Sounds like something wasn't put back. Maybe a coupling capacitor. Start checking all the ones you replaced, one by one, and make sure they are where they are supposed to be.
The hum you hear is actually normal with tube radios.
>>984322
You should probably hit the tuner with some DeoxIT regardless.
>>984354
So it's most likely that I soldered a capacitor to the wrong connection? I'll check them all...after I learn how to read the damn schematic and decipher that rats nest of wires. Glad to hear it's probably not the tubes or anything like that. It couldn't be a resistor could it?
Silence can be a lot of things, usually some link somewhere is wrong or open.
>>984363
Could be. I'm thinking you either soldered something in the wrong place, forgot to put one back in, or disconnected something by accident while working on it.
So the next question is, how the fuck do i decypher the schematic? do i just follow the connection lines and look up which capacitor is in each line? Because none of the shit on here is in the spot its supposed to be in. Pic related, heres the schematic
>>984874
Schematics are not like maps, they are like directions. They don't have every curve in the road and every distance listed, nor are they to scale. Its more like take the left fork off of that switch and follow it until you reach the 240 mA capacitor, then follow the lead with the red resistor on it until you get to the power supply.
>>984874
Without all the tools and know-how, trouble shooting becomes a shotgun approach. Without a great deal of luck, you're just going to end up frustrated.
Take the time to tackle a Ham radio text so that you can come at this with an understanding of how each part of the radio functions.
Here, this is about as close to the cliff's notes on radio repair as you're going to find. It walks you through stage by stage.
http://www.radioremembered.org/rfamp.htm
>>985004
Would it be bad form to just modify a modern radio to use the vintage controls while leaving the antique intact until I have the time, money and knowledge to properly repair it? It's a nice piece in great condition. I'd hate for it to sit around collecting dust into the unforeseeable future
>>985008
Also thank you, although extremely hard to understand, this is a good start
You can check if the local oscillator is running by placing another AM radio near it tuned to the top of the band. Tune the old radio across the band and the other radio will pick up the local osc 455khz above where you are tuning. If its working when it passes as you tune.
Apart from that you should be able to inject and/or detect a signal at the volume pot (R12). Get tube datasheets and measure expected voltages on the tubes.
Don't be tempted to make adjustments to the IF transformers or trimmers until its working.
Be aware these things contain dangerous voltages so take due care.
You can also inject IF if you have a source of 455khz.
>>985060
>Would it be bad form to just modify a modern radio to use the vintage controls
Yes.
Fucking figures it out. I followed the circuitry starting with the antenna because it wasn't giving out any signal. Traced it to the pentagram converter tube who's number was 6a8g. Checked all the solder which was fine, but when I turned the light off, and the radio on, that was the only tube that didn't light up. Further inspection showed that the filament was broken inside. Another tube was flickering along with the motor boating. Shut the radio off immediately and ordered replacement tubes for these two. Thanks guys, couldn't have figured it out without all your help. When I get the parts in by Wednesday I'll give you a status update
