Hi everyone. I’m having an issue on my F14 Tomcat where, during gameplay, switch 55 (General Yakov) and sometimes (not as often as switch 55) also switch 47 are being triggered just by hitting the left flipper, switch 63. During gameplay, it happens very often. Sometimes every time you hit the left flipper. In test mode, it doesn’t happen at all for some reason. Ive tried for days to get it to happen in test mode. All three switches are on the same row in the matrix.
I originally suspected an incorrectly gapped switch that was making intermittent contact from vibration. I pulled switch 55 off of the bottom of the table and gapped it properly. The problem remains. I even disassembled the switch stack. There was absolutely no way that the switch could be making contact.
Even with the switch hanging from the table with an inch between the blades, the problem persists. Like I said above, in test mode, it doesn’t show that any other switches are being activated. I’ve tried test 5, switch levels, and test 6, switch edges. Once you start a game, it’s immediately obvious that something isn’t right. The first four or five times I hit the left flipper, it starts scoring points as if those other switches are being closed too. The sounds are activated and in the case of switch 55 for Gen Yakov, the kicker solenoid is activated too. After the first four or five flipper strokes, it happens every handful of times the flipper button is pressed. It seems to be connected to the lower flipper, not the upper flipper. If I push the flipper button gently enough to activate the lower flipper but not the upper flipper, the problem happens. If I hold the left flipper button in and let it out slowly so that the upper flipper is cycled but the lower flipper is held, the problem doesn’t happen.
I have a logic probe, a DMM, and a small o-scope. I tried looking at voltage through connector 1J8 pins 7, 8 and 9 with my meter. Pin 9 is the column with the left flipper. Pin 8 is for the column with the Gen Yakov switch. With my meter on C53 in the flipper circuit, the voltage is steady when the flipper activates and the General Yakov switch doesn’t. When the flipper is pushed and the general also activates, the voltage on the flipper circuit jumps a bit and then settles down after the General Yakov sounds are done playing. It does this when the general switch is physically closed and also when the intermittent issue is happening. I’m not near the machine right now so I can’t give any specific voltage numbers off the top of my head. I also tried my logic probe on U38 and U40 to see if I could see anything going high when it wasn’t supposed to. Unfortunately, every pin I checked stayed low while cycling the left flipper.
The fact that this is so intermittent is my issue. If it was a mechanical issue or a shorted transistor, I could find it and fix it.
I don’t think this is related to switches or the harness but I’m going to build a switch matrix tester to rule those out.
Do any of you have any other ideas? Ive attached a pic of the MPU schematic I’m working with and a link to the manual.