I cleaned this QDI EXPLORER II motherboard :
It was already working, but it was full of grime and it seems something corrosive leaked on its back (probably a dying 486 sitting on it). Thankfully that stuff cleaned quite well and left only a few dull looking solder joints, but traces and vias weren't damaged.
Then I wanted to clean some more boards I had laying around (all boards came off a big lot I had bought in october 2019) :
this pcchips m577
(With some greasy looking stuff on it ...)
this 286 motherboard
Again there was some kind of greasy stuff on it
Also the two RAM slots at the top used to be green because of some battery leakage that also probably came off another board stored in the same box it's been sitting in for a decade or two ; but it cleaned quite well as you can see. The previous owner also took off two crystals off the board 🙁
And finally this GMB-486SG v1.1 486 motherboard which suffers from a battery leakage (its own this time)
After the cleaning they came back like this 😀
After further testings :
the PCChips don't seem to power the CPU at all, but I noticed that some capacitors got removed (and also it may be misconfigured)
the 286 came back to life after I installed a 24MHz crystal 😁
the 486 doesn't POST even after installing a new keyboard and AT connector (the old ones were corroded). I also fixed two dead traces, but the rest seemed ok ... I'll have to investigate some more to figure this out (I'll probably take a look underneath the KBC socket)
Edit :
ah now I see why the pcchips doesn't turn on the CPU, look at Q18
The transistor seems to have blowed up (probably a lack of cooling considering it's a super socket 7 board with no cooler installed for these ...). It's a PHD45N03 LT transistor ... I'm going to try to find a replacement for it !