This isn't the most complex of repairs but it was certainly labour intensive. Happy to have acquired this MK2 soundboard. It was highly corroded when received, the orange is obvious but there was also a substance beneath the logic chips.
I decided the only way to go was to do this properly and rebuild the board.
So I removed all the rusty resistors, badly damaged capacitors and the corroded amp. I also fluxed out all around the logic chips to remove the mystery substance around and beneath them. I also cleaned up the ROM chips, however, U2 was shot. I replaced U2 and also replaced the socket (that was shot also).
Here is the board partially stripped back.
After an eternal wait my 10uf axial capacitors finally arrived and I could fully populate the PCB.
First test and it wouldn't boot - so I tested all the socketed components and found they were good. I was getting logic around the PCB but I found there was a weak short to ground on the 74HC541 chips at U21, U22 & U23. I removed and replaced those chips and found a lot of the mystery substance substance still beneath the chips mixed with flux. I heated the board up and removed whatever came out from beneath the chips.
Repopulated the board and was greeted with sound but no LED light. Replaced the faulty LED light and now it's fully working.
Another one saved from possibly going into land fill.
I decided the only way to go was to do this properly and rebuild the board.
So I removed all the rusty resistors, badly damaged capacitors and the corroded amp. I also fluxed out all around the logic chips to remove the mystery substance around and beneath them. I also cleaned up the ROM chips, however, U2 was shot. I replaced U2 and also replaced the socket (that was shot also).
Here is the board partially stripped back.
After an eternal wait my 10uf axial capacitors finally arrived and I could fully populate the PCB.
First test and it wouldn't boot - so I tested all the socketed components and found they were good. I was getting logic around the PCB but I found there was a weak short to ground on the 74HC541 chips at U21, U22 & U23. I removed and replaced those chips and found a lot of the mystery substance substance still beneath the chips mixed with flux. I heated the board up and removed whatever came out from beneath the chips.
Repopulated the board and was greeted with sound but no LED light. Replaced the faulty LED light and now it's fully working.
Another one saved from possibly going into land fill.
