Help needed with a Pye P35 valve radio

Hi, I am planning to restore the above as I can get hold of the components. The radio receives lw/mw and 6 sw bands.

It was working ok and then the volume suddenly dropped to about half that it should be, the potts have been cleaned and are not noisy.

The radio picks up all the channels it did previously but it is quiet and turning the volume pott up or down does pretty much nothing.

Could anyone point me in the general direction of which component/s to look for as the culprit/s?

Any help would be massively appreciated.

I will post the schematic on alt.binaries.schematics.electronic entitled 'Pye P35 Schematic'

Thanks for any help guys.

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Based on what you're describing, the first place I'd look would be the heater of the output amp tube. Betcha a nickel the filament died...

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Reply to
Don Bruder

If the audio output tube died, you'd get no sound at all, not about half- volume. It's not uncommon for old carbon resistors to increase in value. Coupling capacitors develop leaks, but that usually causes obvious distortion. The nice thing about troublshooting tube gear is that you can measure resistors in-circuit (With the power off!). If you have the schematic, it probably gives DC voltages; knowing which voltage is out of spec you can usually deduce which component might be bad.

Reply to
Stephen J. Rush

Thanks to you both for your replies (I'm on another pc that's why my name's changed)

I didn't know that you could test resistors in-circuit with tube gear-nice tip! My friend has the same model of radio and has offered me the chance to use his tubes to test in mine.I am concerned that if something has damaged one of my tubes it might blow one of his-do you think this is a possibility?

Reply to
Sky

Tubes are mechanically fragile, but electrically rugged. After my post, I noticed that you'd posted the schematic. With a transformer power supply, you don't have to worry about a short in the filament string blowing one of the filaments, as sometimes happened in transformerless sets that had the filaments in series. About the only thing that could damage a tube is a shorted coupling capacitor that dumps one tube's plate voltage onto the following grid. Even that won't kill a tube instantly. If you're still worried, swap your tubes, one at a time, into your friend's radio.

Having a working set of the same model lets you probe DC voltages to compare with yours. Coupling capacitors between audio stages usually leak or short, but I've seen them fail open, which will leave the DC voltages unchanged but block the signal. An old trick is to turn the volume control up and touch its center terminal with a finger. A loud buzz of AC coupled through your body capacitance means the the whole audio half of the set is working. Just be sure you don't touch anything else; plate and screen voltages are high enough to bite you.

Reply to
Stephen J. Rush

Me again - I would not risk it. If C40 is leaky and putting a positive voltage on the EL33 grid it will not be happy. Check the voltages first - guessing about

5v on the EL33 cathode and 260v on the anode. If your weak volume is especially lacking bass then c40 may just have reduced in value - try a parallel cap (correct voltage rating).

Geo

Reply to
Geo

damaged

possibility?

voltage

about

reduced in

Thanks for the help guys, I found that r12 had gone open. I changed it and the radio sounds great now. Still going to change all the paper caps etc though.

By the way sorry for multi posting -I posted in sci.electronics.repair- I've since learned the rules.

Reply to
Sky

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