Gottlieb operation Thunder, single switch not firing

[dudeyds]

Hi everyone,

I've been working on my first Pinball machine, and I'm finally up to my last issue before I make a big parts order from America,

The left Pop bumper doesn't seem to be firing, I went into the relay test mode, and manually firing it works fine, so I went into the switch matrix test mode, and it looks like the switch isn't beign regsitered.

I used a multimeter to check continuity and the switch seems to work (compared to the right pop bumper)

I have the repair manual and have watched several videos on how switch matrixes work, I understand the basics but I'm a little lost reading the schematic.

The switch has continuity up to the board I've pictured, which is the Diode board for the switch matrix

I've tried bridging pins 11 and 12 of the matrix, so that when the right pop bumper is fired, the left one should trigger too ,but that doesn't seem to do anything.

Honestly I think I'm slightly out of my depth, most of the issues I've googled have been around entire strobe lines being out, or when one switch fires another does. I assume just one switch not working means it should be something isolated and simple to fix.

Could anyone give me any advice as to how to isolate the problem?

Thanks so much.

 

[Jay Walker]

Hello,

As I see the schematic for the switch matrix, the return wire from the bumper switch doesn't venture onto the circuit board with diodes; it wouldn't need to, as it's common to all the switches on that return. There are five other playfield switches shown on that line, the up-kickers, left outlane and top left ramp. I'd check for continuity of the return (colour '600', which I read as Blue-black-black) among those switches or even back to the main control board, A1 J5 pin 8 (unplug the connector from the board though). If that's okay, I'd wonder about the diode for the bumper switch, but your link between pins 11 and 12 of the diode board seems to have eliminated that. The link would supply a known source of 'Strobe 1' to both bumper switches. But even then, each switch would only operate its own bumper, since they're on separate returns.

I'd agree that just one switch not reading, while others on the same 'Row'/Strobe and 'Column'/Return do, isn't likely to be anything major. A failed open-circuit diode, broken wiring, or the actual switch contacts themselves are the usual suspects (even sealed microswitches aren't immune, there was a spate of bad ones at Williams during the 90's).