Please help my Pye P35!

[eu.thundernews.com]

Hi, I am planning to restore the above as and when 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.

 

[James Sweet]

Hi, I am planning to restore the above as and when 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.

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?

 

[eu.thundernews.com]

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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?

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.

 

[Geo]

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.

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

 

[James Sweet]

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

 

[eu.thundernews.com]

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.

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

 

[eu.thundernews.com]

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 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

 

[Sky]

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

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)

 

[Sky]

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

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.

 

[James Sweet]

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.

 

[eu.thundernews.com]

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.

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

 

[b]

Hi, I am planning to restore the above as and when 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.

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.

 

[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

 

[James Sweet]

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..

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