First post, by quicknick
Ok guys, so i had this board arrive to me a few days ago. It was seriously corroded - thick and dark green stuff covered many of the traces and vias around the battery on both sides of the board. I decided to try and repair it, since it's my only 386SX board and because... why not?
I tested it as it was - of course it was completely dead. No beep, no codes on the POST card, nothing.
(Photo from the seller. So small you couldn't see the extent of the damage. Or the bent pin on the 387SX 😠)
It took me a few hours to do the following:
-remove all components from affected area
-clean the board, (water/vinegar/isopropyl), use fine sandpaper to remove all corrosion and solder mask, use needle to clear the vias from gunk
-reinforce a grand total of 43 vias using legs cut from scrap ICs, bent and soldered on both sides
-reinforce all affected traces using solder, and thin copper wire where needed
-replace the components, using new diodes, resistors and capacitors. I had to reuse the transistors and inductors because i had no replacement for them.
After the attempted repair, and using the original (Award) bios, the board seems as dead as before. On very rare occasions the POST card displayed some codes (EC, C4, FA, FF) - but i got no beeps and no video initializations, and the FF code seems a bit nonsensical as it was displayed only once, right away at power on.
Searching the net i found another bios (AMI) for the 386SX / OPTi 82C291 / 82C206 combo. Burned this one on a fresh EPROM, and using this i get the following behaviour at each power on: POST card cycles through a few codes (04, 05 ... all the way to 13, and then 35 where it gets stuck). The thing is that it seems rather slow at this, it takes quite some time to get to code 35 (around 20 seconds, or 40 if i short the Turbo pins), so i left it for over an hour to see if it moves past 35, but it doesn't. According to the book, code 35 stands for Display mode set complete. BIOS ROM data area about to be checked.
Memory below 1MB calculated..
So, at this point i'm open to any new idea, as i'm out them...