A4000 cap change + NEW CAPACITOR MAP

[pauli]

Hi

Some time ago i bought A4000. I knew when buying it had some minor problems with audio..

Truth is, these are 20 year old machines. If they have "minor problems" and they have newer been fully restored, you can expect some quality time with soldering iron.

This one had electrolyte leakage all around audio parts and on some parts of video output. Luckily, battery had been removed before any damage.

First thing I noticed when gathering list of caps I need to buy, is that nobody mentions physical sizes. This is also required information, to make sure cap fits on the pad.

Also, Audio part needs bipolar(non-polar) caps. Originally A4000 has regular caps, which is not right.

I found original cap map from amibay, but can't find it anymore. :/
Cap map with my size remarks is here:
http://www.suikka.net/~pauli/amiga/smd/a4000d_motherboard_revb_capacitores_rev2.png

Also, here is some cap replace photos. Last photo should be with flux cleaned.. i will post it when all caps replaced.

note pcb need cleaning. After cleaning with alcohol, it will look like new.

 

[hese]

Also, Audio part needs bipolar(non-polar) caps. Originally A4000 has regular caps, which is not right.

Is that so?

The audio is centered around 2.5V on the primary side of those caps, and around 0V on the secondary side (AC coupling), so they are constantly charged to around 2.5V, and will never see any negative voltages, which is why they don't need to be bipolar.

http://eab.abime.net/showpost.php?p=846291&postcount=12

 

[pauli]

Could be .. In my a4000 most badly leaked caps were those four I marked to need bipolar caps. I guess it doesn't hurt to use bipolar even if it's not really required.

Anyway. My point with this thread is that capacitor lists need to mention physical sizes too.

BTW, just installed hdd to my repaired a4000 Everything works perfectly. Even audio is now fine.. it originally had some major pcb damage.

-Pauli