switch matrix wiring issues

[robm]

I have a FishTales where switches 34,44,54 and 64 don't work - yet 14 (tilt) does and 24 is always closed (as should be).

I've done the tests on pinrepair jumpering across 207 and 209 and they test OK, so this should indicate the problem is on the playfield rather than the CPU (i replaced U20 and 18 anyway).

I can get continuity from the white/yellow wire from switch 14 (tilt) to CPU connector J212, but can't get any continuity to this pin from any of the other switches.  Continuity between switches 34,44,54 and 64 is fine, but none between any of these and 14.

What i have also discovered that may help is that when testing the corresponding diode D21 on the Coin door interface board (just near the tilt mechanism), is that it tests as 0.9V when all the others test OL (when reading the other way for the diode test they all test OK at 0.5V)  If i disconnect plug J1 from the coin door interface board, this diode tests OK (i have replaced this diode as well), so does this indicate a problem with one of the switches or wiring downstream? ie: switches 34 - 64.

I tested each of these switches one by one and they all work OK (continuity when closed, none when open).

What i can't work out also is that the yellow/white wire from J1 on the coin interface board seems to go straight to CPU J212, but can't see where this all joins to the yellow/white wire for switches 34-64.

I'm tempted to jump this yellow/white from 14 to 34 and see what happens - is this a bad idea?

Thanks

Rob

[Strangeways]

Looks like the obvious culprits are covered. I had the same issue on a DR Who and it was a real pain to trace - ended up being a switch was shorted to a lamp socket and it took the entire row out. I had just replaced the globes and then it started playing up.

[MartyJ]

Hi Rob,

Switch matrix issues can be good fun 

As Nino said - you're well on the way - eliminating the CPU board is always a great start.

Me personally, I'd test continuity from J209 (pin 4) - white/yellow to the switch for that row closest to the back of the playfield - most likely 64 or 44 and work your way down from J209 on the playfield.

Also check it hasn't been pinched on anything (including headbox if its been down recently).

[robm]

We have a winner!!

Thanks MartyJ, got no signal from J209 p4, looked in the bottom of the cabinet and the 1st thing i saw was a broken yellow/white wire that must have been pinched with the head down.

Thanks heaps - its funny how so many errors that pop up on machines are so simple!

Rob

[MartyJ]

We have a winner!!

Thanks MartyJ, got no signal from J209 p4, looked in the bottom of the cabinet and the 1st thing i saw was a broken yellow/white wire that must have been pinched with the head down.

Thanks heaps - its funny how so many errors that pop up on machines are so simple!

Rob

Good work!  Enjoy the FT!