I am trying to track down a switch matrix issue on a JD, before I burn it as firewood!
Having researched switch matrix issues, I have managed to draw a rectangle around the ‘rouge’ switches and I think it’s a diode issue, but tracking it down has been thus far been impossible.
What is happening; is when SW18 3 Bank Targets is hit it also activates the SW14 Tilt-bob, also when the SW38 Subway Enter 2 is activated it triggers the SW34 Inside Right Return. Thus making the rectangle on the matrix.
So I have replaced a diode on the first of the three SW18 3 Bank Targets (others tested fine so did not do these), the diode on SW34 Inside Right Return & SW38 Subway Enter 2.
All of the diodes taken out tested fine, so they clearly were not the issue.
Looking over other switches all diodes look to be on the correct way round, added to this I have tested a number in place and the appear fine.
I have put in a known working coin door interface to eliminate the tilt diode and other coin door and front buttons.
SW58 Drop Target ‘E’ is flaky as it flickers on and off, so I plan to reflow the solder. But I did simply disconnect the connector to that board and still had the switch problem.
Some switches in column 1 and row 4 are optos, do these have diodes if so where and how do I test them?
Any other suggestions as to what to do, test or how to work through this issue, its driving me mad!