Board booted to 'backup ram read error 5555-5500' message.
Found battery corrosion, once cleaned up saw damage to pin 9 of a surface mount 74HC32A;
After scraping off the corrosion, touching a scope to this pin caused the board to boot. When in test mode all seemed well other than missing inputs on coin and service buttons. Scoping the damaged pin caused these inputs to work again... even though the scope trace itsself didn't move.
I suspected the chip may have been earthing slightly to the scope probe, as it was the contact rather than pressure.
There was no visible trace from the pin , so it was either under the chip or tied to a hidden layer.
I fluxed and tinned the pin and the board worked, must have re-established the bad contact. Just need a neo cart now
Found battery corrosion, once cleaned up saw damage to pin 9 of a surface mount 74HC32A;
After scraping off the corrosion, touching a scope to this pin caused the board to boot. When in test mode all seemed well other than missing inputs on coin and service buttons. Scoping the damaged pin caused these inputs to work again... even though the scope trace itsself didn't move.
I suspected the chip may have been earthing slightly to the scope probe, as it was the contact rather than pressure.
There was no visible trace from the pin , so it was either under the chip or tied to a hidden layer.
I fluxed and tinned the pin and the board worked, must have re-established the bad contact. Just need a neo cart now
