In the PDF I created, I show pertinent sections from two schematics: one drafted by Apple and another reverse-engineered by BOMARC. Both schematics are electrically the same. They are just drawn differently. I highlighted the relevant traces in yellow on both schematics.

Click to expand...

Victory! I got the problem fixed. The schematics got me started scrutinizing the motherboard and I found out that capacitors C6,C9 and C10 had been leaking.

I replaced the 3 of them and, miracle, the reset is now fully working again.

Thanks for all the pointers and the schematics, it helped.

I'll look into replacing all the other capacitors. However I must say my motherboard is pretty butchered, I'm glad the Mac is still working. My soldering iron I think is way too big, a generic Radioshack 64-2070 25W. I really made a mess desoldering the old caps.

Anybody has a suggestion for a budget soldering iron ($20-ish) more appropriate for motherboard work?