Quoted from Jenk540i:Game started losing the pinballs. After doing as much as I know to do I have determined that I have a column of opto switches (#31-38) issue. Switch #31 registers but not the other 7 switches.
My skills are limited but Iām willing to try more diagnostics. Next step(s)?
This is either going to be a broken wire or a failing 16-Opto board, obviously checking for a broken wire is going to be easier than troubleshooting the board, so lets start there:
Each switch contains a pair of optos, one LED board (transmitter) and one Photo Transistor board (receiver). All of these optical switch board pairs are part of a larger assembly (Borg ship, VUK, Gun, etc...), these assemblies all contain Molex type connectors as they were designed to be dropped in connected to the main wiring harness with no soldering. This is important because any single wire that would effect large portions of the column would have to be broken at the molex connector on the wiring harness where they daisy chain to the next connector; there are two daisy chained wires that can do this, these are the Ground (BLACK) wire to the Photo transistors and the +12V (GRY-YEL) wire to the LED assemblies.
On the 16 Opto PCB assembly, do a visual inspection of C6 to look for bulging or leakage, this can also appear as a darkening of the PCB around the capacitor; failure of this capacitor can cause many opto issues and is something that should be replaced if its still the original.
Mechanicsville, VA
