Woody wrote:
"h.tees" wrote in message
...
"Rob" wrote in message
...
I've just plugged in a Quad 34 preamp that's been unused for a few
years. When I turn the volume control up there's a series of loud
high pitched clicks through the speakers, a bit like LP static
discharge maybe. It was fine last time it was used.

Does this sound like an expensive problem, or would I be better off
punting it on ebay, and buying another (about £80 it seems)?

Thanks, Rob
It is the volume control that needs replacing. It's a very common
problem
in most audio circuits of that age and the design of the control
doesn't
help. No need to bin the preamp, just find another volume control.
Maplin will sell something suitable for around £2-3. I would solder
it in or
get a friend who can - you will save a fortune.




I don't think that may necessarily be the case. Quad were quite good
with their circuit design, and if the volume pot interfaced to a high
impedence load then it may not be the pot as such circuits were not
prone to that type of noise.

I suspect the problem here is dried out and/or leaky electrolytic
capacitors. Clicks whilst playing are typical of capacitors that are
leaking and affecting d.c. bias conditions.

I would agree that crackles whilst playing are also typical of a volume
pot that has gone noisy, but it should not do it at minimum volume where
the pot wiper is effectively earthed.

The loss of one channel that plays when the mono button is pressed says
one pre-amp is not working. I had a Q33 which had plug-in circuit
boards: it is just possible that this unit may be of the same
construction and that the boards have become dislodged. It might be an
idea to get the lid off and see if this is the case - if it has plug-in
boards even remove them, clean the contacts if necessary and put them
back. It might just cure everything.

Otherwise I stay with the cap theory.



Thanks. Wouldn't surprise me given the age, and the fact it worked
before. Only one channel is working in stereo, with sound coming out of
both speakers in one side mono when the mono button is pressed; and,
there are no plugin boards except the phono - it happens on all inputs.
FWIW I took the top off and everything looks brand new and shiny - no
bulging/leaking caps for example.

Rob