I installed LEDs in a new to me Dr. Who and now it will not play.
The message initially was 'Pinball missing 3' (its a 3 ball game, meaning it can't find the 3rd ball). All 3 balls were in the trough so it was potentially a switch issue - nothing to do with missing balls, so I replaced switch 3. Then, occasionally the slam tilt would engage and the machine would just display 'slam'. The slam tilt is disconnected. I ran switch edge tests and it turns out that ALL switches in that column (column 2 on the switch matrix - Green/red wire) are out. These switches include slam tilt, coin door closed, ticket opto, #24 (doesn't exist; always closed), trough 1, 2, and 3, and the outhole.
I also replaced the U20 chip on the board with moderate success, each of the switches now registers in both the edge test and the single switch tests, but the same message remains and it will not go past 'searching for pinballs'. It now does a 15 second countdown, ejects all 3 balls, then displays 'out of order'. I should note that prior to swapping the U20 chip it did not countdown at all, it just showed 'searching for pinballs' and '15' but never counted down. Progress???
I have searched all over for a shorted wire in that particular column, so unless there is a broken wire inside the insulation I can't see one. Would it be worth replacing all of the diodes on all of those switches, just in case?
The other thing I am considering is replacing the U14 chip as well (not socketed, ugh) because I have read that if the U20 fails the fault could continue on up the board. The board itself looks relatively new and was probably replaced in a previous life.
At this point I'm not sure if I have 100% determined if it is a board vs. under playfield issue; I have only visually and not electronically eliminated the PF as the problem. I have read a few guides on doing this but I'm not sure I understand the 'jumper method' for example.
Any thoughts, advice or info is appreciated.
The message initially was 'Pinball missing 3' (its a 3 ball game, meaning it can't find the 3rd ball). All 3 balls were in the trough so it was potentially a switch issue - nothing to do with missing balls, so I replaced switch 3. Then, occasionally the slam tilt would engage and the machine would just display 'slam'. The slam tilt is disconnected. I ran switch edge tests and it turns out that ALL switches in that column (column 2 on the switch matrix - Green/red wire) are out. These switches include slam tilt, coin door closed, ticket opto, #24 (doesn't exist; always closed), trough 1, 2, and 3, and the outhole.
I also replaced the U20 chip on the board with moderate success, each of the switches now registers in both the edge test and the single switch tests, but the same message remains and it will not go past 'searching for pinballs'. It now does a 15 second countdown, ejects all 3 balls, then displays 'out of order'. I should note that prior to swapping the U20 chip it did not countdown at all, it just showed 'searching for pinballs' and '15' but never counted down. Progress???
I have searched all over for a shorted wire in that particular column, so unless there is a broken wire inside the insulation I can't see one. Would it be worth replacing all of the diodes on all of those switches, just in case?
The other thing I am considering is replacing the U14 chip as well (not socketed, ugh) because I have read that if the U20 fails the fault could continue on up the board. The board itself looks relatively new and was probably replaced in a previous life.
At this point I'm not sure if I have 100% determined if it is a board vs. under playfield issue; I have only visually and not electronically eliminated the PF as the problem. I have read a few guides on doing this but I'm not sure I understand the 'jumper method' for example.
Any thoughts, advice or info is appreciated.
