Had a look at that article, and it is incorrect about using a non-polarised capacitor.
It's perfectly normal to use the polarised capacitor Commodore fitted. In fact you could use either, but since the non polarised ones are usually bigger, more expensive and there were exsisting polarised capacitors in the design, it made sense to do what C= did.
The negative side of the capacitor is biased to ground, so providing the bias on the op-amp's input doesn't get messed up, the circuit is fine.
The facts are that it would appear to be a very large bad batch of electrolytics, or more likely just a bad quality capacitor. Apparently various manufacturers have had electrolytic chemical problems over the years.
I've repaired a lot of A4000T, A4000D, CD32 and A1200 with this problem. In almost all cases it's only the 22µF capacitors, and not just the ones in the audio output section.
From memory there are around 5 of these 22µF capacitors in the A4000D, which I have all seen with leaking problems.
Some of the other SMD electrolytics can have the fault too, but from experience, the 22µF ones are definately the worst.
The problem should not occur on the A3000 as these are all through hole components. Only the surface mount capacitors in the A4000D/T, A1200, A600 and CD32 would appear to suffer from this leaking problem. Leaded capacitors usually just tend to "dry out" rather than leak.
The biggest cause for concern in almost all Amiga models is the RTC battery failing.
These batteries are generally rated for a life of around 6 years, but some of the ones out there now will be double that age.
There's a very high chance of the battery leaking corrosive material onto the motherboard which can cause a number of faults.
I'm actually in the process of writing a guide on this, my work so far is online at:
http://amiga.serveftp.netunder the battery replacement section if anyone wants a look.
Lots more technical info to be added as I get time to write it :-P
Anthony.
