[sdiy] strange PCB faults, was:OTA question

[Harry Bissell]

Were they caps that were defective of manufacture, were they improperly installed
(ie left to shake with ambient vibration) ?

Were they misused (ie AC signals through a polarized electrolytic ???

Its really not that common, although possible. That is not the first thing I'd be looking for
in a failed amp.

H^) harry


----- Original Message -----
From: Graham Atkins <gatkins at blueyonder.co.uk>
To: Harry Bissell <harrybissell at wowway.com>
Cc: Ingo Debus <igg.debus at t-online.de>, synth-diy <synth-diy at dropmix.xs4all.nl>
Sent: Fri, 17 Sep 2010 11:53:51 -0400 (EDT)
Subject: Re: [sdiy] strange PCB faults, was:OTA question

On 17 Sep 2010, at 15:51, Harry Bissell wrote:

> Electolytic capaciotrs don't usually leak. They dry up and then
> pop.  If you didn't see a blown open can, or one that is bulging at'
> the top (or ends) its probably not the source.

I have seen electrolytics leak. There is a known flaw on the Quad 34
pre-amplifier. The capacitors they used for AC coupling leak down
the legs onto the PCB pads. This causes corrosion and has been
known to cause joint "failure" in worst cases. You have to desolder
and scrape the pads before re-tin and repair.

Graham


-- 
Harry Bissell & Nora Abdullah 4eva