A3640 problem & A4000 questions

[Zac67]

Resoldering new caps is rather easy, but removing them can be hard (to the pads). I clipped the upper part of the caps, removed the plastic base and then desoldered the rest - killed two pads that way, which I had to repair afterwards.

Reportedly the easiest way is to use two soldering irons to desolder both sides simultaneously.

ALL but the very last A3640s had reversed caps. After the design was finished, they were added just before production began - and C= didn't notice until years later...

[Zac67]

Just for completeness: NEARLY ALL A3640 have three electrolytic capacitors reversed (only the very latest batch was corrected): C105, 106, 107. The silk print is wrong, use a simple multimeter to verify. Sometimes the caps just dry up and that's it, but often they leak and damage the board.

http://joj.home.texas.net/amiga/amiga03.html
BBoAH

[Zac67]

The silk screening is always wrong for these caps - it wasn't changed when the error was discovered. Just use a multimeter, set it to low Ohms/beep and check whether the cathode (-) is connected to GND (like on the other capacitors) - or rather the anode (+)...