"Adrian Ball" wrote in message
...
On Sun, 06 Jul 2008 18:30:16 +0000, mick wrote:

On Sun, 06 Jul 2008 13:08:28 -0500, Adrian Ball wrote:

Help, please!

My much-loved 30 year old A60 has recently developed a fault, but
having no electronics experience, I have no idea how to diagnose it.
If anyone can at least give me a clue, and an idea of how easy it
might
be to repair, I would be very grateful.

The symptoms are that the left channel, after the amp has warmed up
distorts very badly. This is only when using the loudspeakers - the
headphones output sounds fine.
The symptoms are the same from any source, using either the switched
or
non-switched terminals - I've also swapped speakers to confirm that
the
left speaker has not developed the fault.

Thanks in advance for any advice - I really don't want to dump this
amp...



There is a service manual for this amp he
http://www.retrohifi.co.uk/ar_cambrige.html

I realise that it might not mean much to you, but it could be
invaluable
for someone trying to diagnose the problem. It may be worth your
while
to print it out then take it to a local electronics "bod" to have a
look
at.

Thanks for taking the time, it's much appreciated! I had found that
site
earlier tonight, and thought "this might prove useful to someone that
knows what they are doing" - just got to find the local electronics
bod
now...

Cheers,
Ade.

--
Adrian Ball
http://www.hp5.co.uk/
Do not use spam-trap - please use:-
ade at hp5 . co . uk


A&R became Arcam, so you could ask their Service Dept. Failing that (and
not many people know it) Richer Sounds also have a Service Dept and may
be able to help you.

It sounds to me like a bias fault - one of the output transistors is
getting hot and a sensor - usually a transistor fitted into the
heatsink - is sensing the rise in temp and trying to switch the output
transistor off. Net result is a seriously distorted output.

The headphone output on good quality amps often came from its own source
to keep noise and distortion levels down.

I notice you are in Wirksworth. Lowe Electronics on Chesterfield Road in
Matlock are an Amateur Radio equipment supplier and probably don't do
repairs any more but they may well know someone locally who can help you
if all else fails.


--
Woody

harrogate three at ntlworld dot com