a3640

[orange]

Is there some easy way of telling if A3640 in Amiga Technologies A4000T suffers from badly_polarized_capacitors? (do all AT A4000T have bad/good capacitors?) :-?

[Zac67]

Easy: measure resistance from caps (+) to known GND, e.g. around screw holes. If it's low they're wrong. C104 & C105 real gnd is left etc.

[orange]

arrgh, it looks bad:
http://orange.users.sbb.co.yu/Amiga/PA250003.JPG

(((

the black stripe is soldered on +, so its wrong, right?
but cpu works fine, I really don't wanna break it trying to 'fix it'... should I just ignore it?

[KThunder]

i would just keep an eye on them, you will see around the solder pads when they start to leak IF they do. if they do and you are good at soldering then replace them before they cause damage.

[patrik]

@orange:

I think the mask printed on the A3640 pcb has the wrong polarity printed for part of the capacitors and was the reason A3640s used to have a part of its capacitors reversed in the past. Thus the mask doesnt match the polarity of part of the capacitors on your A3640. Anyhow, to know for sure - just measure as already suggested.

(edit):

Your capacitors are atleast turned the same way as on a A3640 I have here which has had its capacitors replaced and polarized correctly.


/Patrik

[Zac67]

Yes, the silk screen is wrong. The caps look AOK!

[orange]

great, thats a relief  :-) , thanks
but then the caps on Big Book of Amiga Hardware A3640 are wrong..
It would be a lot easier if someone simply posted photo of correct orientation because the cpu card is not easily accessible with ohmmeter.