I have now
got the CPU up and running, but it was a bit tricky. Someone had already been
working at the board and socketed the Z11, Z12 and Z13. When measuring the
logic levels round these IC’s the levels was far too low, about 2,5-3v and it
turned out that the fellow working at it had put back the faulty IC’s in the sockets.
After changing these three chips I did still had too low levels at some signals
and except for the first three chips I also had to change U4, Z14, Z15, Z34 and
Z35. Then it booted properly and the switch matrix worked in the test. But it wasn’t
possible to start a game, nothing happened when pressing the start button. I
found out that when the ball wasn’t at the outhole switch it was possible to
start a game and when dropping the ball back in the outhole everything worked
as it should, until it was time to start a new game. The cause for this was the
diode at the outhole switch, it was shorted and messed up the switch matrix
when it was closed.
It’s still
a question mark why all these chips was faulty, I haven’t seen so many broken IC's at
the same time before. It might have been caused by an accidental shortage to a
higher voltage somewhere at the playfield or something wrong with the 5V supply. The
5V measures Ok now, but I will take the supply board apart to check for any
cracked solders or anything else wrong, just to make sure.Right now I have taken out the playfield to clean up the inserts and go through all the lamps and mechanics at the underside.
I will replace the battery with an external battery before returning the game
Someone seems to have rested the playfield at these lamp holders causing them to get bended. The holders was also loose from the bracket and I had to solder them in place to get them properly grounded.
