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| 01 May 2008 21:45:59 |
| eu.thundernews.com |
| 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. |
| 01 May 2008 14:44:40 |
| Don Bruder |
| Re: Help needed with a Pye P35 valve radio |
In article <c_pSj.1458$Cr1.1372@newsfe18.ams2 >, "eu.thundernews.com" <blib@blop.flob > wrote: > It was working ok and then the volume suddenly dropped to about half that it > should be, the potts have been cleaned and are not noisy. > > The radio picks up all the channels it did previously but it is quiet and > turning the volume pott up or down does pretty much nothing. > > Could anyone point me in the general direction of which component/s to look > for as the culprit/s? Based on what you're describing, the first place I'd look would be the heater of the output amp tube. Betcha a nickel the filament died... -- Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd |
| 01 May 2008 20:37:06 |
| Stephen J. Rush |
| Re: Help needed with a Pye P35 valve radio |
On Thu, 01 May 2008 14:44:40 -0700, Don Bruder wrote: > In article <c_pSj.1458$Cr1.1372@newsfe18.ams2>, > "eu.thundernews.com" <blib@blop.flob> wrote: > >> 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? > > 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... 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. |
| 03 May 2008 12:39:20 |
| Stephen J. Rush |
| Re: Help needed with a Pye P35 valve radio |
On Sat, 03 May 2008 12:19:33 +0100, Sky wrote: > 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? 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. |