Jonathan,

I don't have access to any of the modules you're referring too,
but in general -- assuming they've been powered backwards,
the first things to go are the electrolytic (or tantalum) caps
near the power connector. Burn markings are most likely
coming from those caps which "crossed over to the dark side".

Replace these first, then work your way down to any other
possible tantalum caps, the IC's, then the transistors...
though there is no definite way of components knowing
which components die first.
YMMV.

_g

On 31 Oct 2010, at 17:16, jonathan.heslop wrote:

> Having recently acquired a damaged A-136, I have now ended up with a damaged A-143-1. At least the Waveshaper was sold as damaged, the A-143-1 was sold as new :(
>
> Channel's 1, 2 and 3 seem fine. Neither of the two LED's on channel 4 light up and the output's seem to do nothing. I noticed on the back of the module channel 4 is the first channel to receive power from the bus. I guess this could be a case of the module's power having been plugged in upside down. The waveshaper had the same problem and replacing the two amp's fixed it. There was visible burn markings on the solder of the waveshaper, channel 4 on the A-143-1 looks fine, I can't viably see anything wrong with it, channel 4 looks identical to 1, 2 and 3. I guess replacing the four chips (Amps ) on the PCB would be the first thing to try
>
> Thanks for any help,
> Jonathan
>