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From: Jim on 27 Jul 2010 20:32
Have you repaired the amp yet?
I sent you a couple of off list messages but they bounced.
I have repaired a few of this type of amplifier and may be able to
help troubleshoot it.
Contact me off list at IFixAudio at GMail.com.

Jim


On Jul 21, 6:51 am, "N_Cook" <dive...(a)tcp.co.uk> wrote:
> Goes into protect mode at switch on.
> Useful info and schema on these G class ampshttp://www.reptips.dk/Reptips/CAUDIO.pdf
>  as well as schema only, on e-service
> One smps supplies both amps and 4 rails, each rail supplies both ch, I've
> cut the "overdrive" rails temporarily and running on +/- 60V.
> Output has about +18V on ch1 for about a second before dropping down to 0,
> so o/p DCsense line to the PIC tells it to go into protect, of whole amp.
> With 15R load then op jump is to about 10V. The other ch2 is fine , no more
> than 0.5V on output loaded or not.
> Same 2 (4 in full operation) rails supply both amps. All electrolytics check
> out ok. Problem fault tracing is 3/4 of the active in this amp shows the
> same 18V or so jump at power-up.
> Disabling the protect line, so the amp powers up, shows nothing amiss after
> 2 seconds, on all main transistors, running at +/-25 V rails anyway. I will
> repeat this now at +/-60 V but as no 1 to 1 correspondence of device
> numbering or posistioning between ch1 and ch2 a bit awkward and I don't
> expect to see any substantial DC differences as has settled down after the
> first couple of seconds. How to zero-in to the problem device . Nothing
> untoward at the pa input but I will tie to ground the next time of powering
> up just to confirm.

From: N_Cook on 28 Jul 2010 03:13
Jim <ifixaudio(a)gmail.com> wrote in message
news:74a484e6-688f-434d-944b-859bdfc3bc09(a)d37g2000yqm.googlegroups.com...
Have you repaired the amp yet?
I sent you a couple of off list messages but they bounced.
I have repaired a few of this type of amplifier and may be able to
help troubleshoot it.
Contact me off list at IFixAudio at GMail.com.

Jim

reply

No valid emails used on usenet
The one with leaky TO92 repaired and waiting for owner to return from
holiday.
Second one initially looked at , problems again in a TO02 device in a
different area of one amp, gone B-C-E shorted so more obvious a problem.
Waiting for owner to return before progressing on that one. Third one not
looked at other than also goes into protect and no obvious problems with the
TO3s , perhaps so well protected that rarely do the YO3s get a chance to
fail.

I will use a valid email account to contact you


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