Please help my Pye P35!

I'd start by checking the volume control itself and solder joints in the audio section. What sort of audio output device does it use? Amplifier IC, or one made of discrete transistors?

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Thanks for your reply, the radio is a valve job made in 1950. The circuitry appears to the eye to have aged well but of course with something this age there could be all sorts of things that need sorting. But I guess the audio output device is valve based.

Hmm... a 'valve job' is something the corner auto mechanic does to your 289 V-8 here in the States ;)

Michael

If you can only guess that "the audio output device is valve based," after seeing the schematic, you should just take it to a repair shop. It's well beyond your near-term capabilities.

If you do continue to investigate yourself, remember that this is an AM receiver. The volume is not only affected by the audio amplifier and related components. Even the RF amplifiers and demodulators can vary the volume. Perhaps the automatic gain control (if any) is malfunctioning.

I see that it has a gram (PU) input. Try this to eliminate the radio section. If the volume is still low then you only have the last two stages to consider (and of course the power supply - but I suspect that will be ok unless the main smoothing caps are leaking very badly and pulling the HT rail low). Assuming you have not caused the fault yourself (all bets then off) and that the audio is low but NOT distorted, my first test (after checking voltages on the valve bases) would be putting another cap across the output stage cathode resistor.

Geo

Does it have paper capacitors? If so then replacing all those is the first thing to do.

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I could take it to a repair shop but I'm not really going to learn much that way.

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I will continue and with the help of people like yourself giving me such useful and relevant information as you have it will make it happen all the faster. You have given me several areas to follow up there and taught me something very interesting. Thank you

Thanks for your reply. The Gram input is low. I haven't caused the prob myself unless it was by moving it or something which would suggest that it was going to happen anyway. And the audio is not distorted. I will follow your advice and see what I come up with.

I started this project with the intention of replacing the components but I realised that I wouldn't learn much about how the whole thing works. Now I'm more motivated than I've been about anything for a long time!

I really appreciate your help as it is this sort of advice that is already helping my understanding and showing me what I need to be studying up on. I'm much obliged! (by the way I'm on a different pc that's why my 'from' name is different)

It has a lot of wax coated caps a friend of mine suggested the same thing, he said that he'd had a similar problem with many vintage valve radios and that quite often it was the caps that were the culprit.

Thanks for your advice, once again I really do appreciate the help of people like yourself because it speeds up my learning and points me in directions that would take who knows how long to find on my own.

You should take this over to rec.antiques.radio+phono, don't crosspost though. There's a lot of guys there with a lot of vacuum tube experience.

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Thanks for the tip there James, I think I'll go have a look now.

1. go on a cap change, especilyl wax and hunts caps - most common reason for poor sound etc
2. check there are no resistors altered in value on the grids.
3. Paul stenning's uk vintage radio site/ forum is a mine of info on this. you can buy cd roms of the service data for cheap

-B.

Sussed it. R12 had gone open, I replaced it and the radio sounds great. Thanks for everyone's advice. I've learned a lot fault finding this problem, and I didn't have to spend a penny! So all round I'm pretty happy.

Gonna change all the dodgy caps etc now.

good news; I hope you checked the current across it- this may indicate WHY it was open!

-B

problem,

My problem is that I'm not quite sure how to work out exactly what current I should expect. I can work it out for simple circuits using ohms law but for more complicated ones I'm not sure where to start. The service sheet I have has a lot of good info but it doesn't show what voltages or waveforms to expect at any points.

I guess this is something I need to work on. I'm hoping that the resistor died because of age and degradation from temperature change..

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By the way you are right about Paul Stellings's site. I'm surprised at how much I've learned in such a small time-motivation I suppose. But it's down to people like yourself and Mr Stelling being kind enough to give us the benefit off your hard earned knowledge

Just feel it after it's been on for a while, if it's very hot, it probably has too much current.