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zenith: 8S463 5808 voltage levels

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » zenith: 8S463 5808 voltage levels
Tom Mitchell
USA  Articles: 6
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31.Jan.20 04:07
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I'm working on a 8S463 with a 5808 chassis. I recaped the chassis, and it powers up, and I alignment, but I'm getting a hum in the audio. 


I looked at the schematic and I see the voltage levels on the schematics. I have the line voltage set to 112V, but none of the voltages line up with the schematics. My transformer output voltage is about 20% higher than they're shown on the schematic.


I'm pulling my hair out, any ideas?

Rolf Beckers
Rolf Beckers
D  Articles: 134
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31.Jan.20 15:10
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Dear Tom,

I assume you also changed all the filter caps too. If so and you still hear the hum, I've two failures in mind to look for. You say that the transformer output is 20% higher than rated. Does it mean you have at the high voltage side over 300V on each of the two windings? If so, does the transformer heat up even without the tubes are inserted? In this case the transformer might have a short circuit between the windings.

The other possibility is that one of the tubes has a short circuit between the heater and the cathode. Just take the tubes out one by one and see when the hum stops. For the 6F6 you have to change to a new one.

Good luck,



Tom Mitchell
USA  Articles: 6
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31.Jan.20 17:28
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I have to set the line voltage to 101.7VAC to get 265VAC on the output of the transformer.. B+ is 205 VDC, and B-  is -0.7V.


I tried pulling tubes to see where the hum was. I pulled the preamp out, and I didn't get any hum out of the output tube. But when I put the preamp back in, I don't get any sound. Maybe I screwed up the output tube. 


The tuning eye still works when I go through the dial.


This is my 1st recap so I have a steep learning curve.