(Topic ID: 293738)

WPC95 Junk Yard - All switches close when fridge VUK fires!

By Scrimmbo

8 months ago


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  • 13 posts
  • 7 Pinsiders participating
  • Latest reply 8 months ago by Crash
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#1 8 months ago

Hey guys, did a little hunting around for a similar thread and couldn't find anything, so I figured I'd start a new one and see if anyone has seen something like this. I installed an led light kit on our junk yard, after I was finished I played a game, made it to the second ball and all hell broke loose once I hit a ball into the sewer! Basically if the fridge VUK fires all the switches on the matrix close. If I unplug the coil the switch problem disappears, but as soon as I plug the coil back in, it fires and all the switches close. Tech alert says all rows are shorted to ground. I unplugged the switch rows and columns at the CPU board and the problem persists. I checked the transistors and diodes in the power driver circuit relating to the fridge vuk, and everything seems okay.

Any Ideas?

#2 8 months ago

Did you install the LED kit with the power on ? If so I suspect you did some damage to the CPU.

If U20 on your CPU is socketed I'd replace it and see if things improve.

LTG : )

#3 8 months ago

You have damaged U20 on the MPU. Get that mod OUT first, then address the fault. Leaving the mod in place is going to compound and confuse your fault finding efforts IMO.

#4 8 months ago
Quoted from pins4u:

You have damaged U20 on the MPU. Get that mod OUT first, then address the fault. Leaving the mod in place is going to compound and confuse your fault finding efforts IMO.

Get the mod out? Like take all the led lights out??? I don’t think that’s necessary in this case. May have caused damage installing while powered on but now that they’re all installed, it no different than going back to the incandescent ones. Rest of advice seems like a good place to start

#5 8 months ago

I did indeed have the power on while doing the LED kit. I had never heard that this could cause problems. With as much of a pain as the wedge led replacements can be (having to fuss with the wires to get them to make good contact) I've always changed them while in lamp test mode. Well, good to know anyway. I will look at U20 in the morning, thanks for the replies!

#6 8 months ago
Quoted from Scrimmbo:

I did indeed have the power on while doing the LED kit. I had never heard that this could cause problems. With as much of a pain as the wedge led replacements can be (having to fuss with the wires to get them to make good contact) I've always changed them while in lamp test mode. Well, good to know anyway. I will look at U20 in the morning, thanks for the replies!

You should never work on any electronic device with the power on. Even very experienced electronic technicians exercise extreme care when they do so.

#7 8 months ago
Quoted from pins4u:

You should never work on any electronic device with the power on. Even very experienced electronic technicians exercise extreme care when they do so.

How can I do a lick test with the power off?!?

just kidding, you are correct, and in most cases I do, but it never occurred to me that an led kit could damage a game.

#8 8 months ago
Quoted from Scrimmbo:

How can I do a lick test with the power off?!?
just kidding, you are correct, and in most cases I do, but it never occurred to me that an led kit could damage a game.

LED kit will not damage a game per say, but unscrewing a GI bulb socket and shorting it to something metal on the playfield most definitely will damage something. When changing wedges to led, I always have the game on. But with the GI unscrewing from the bottom of the playfield, should be done with the game off. I too have learned the hard way...

#9 8 months ago
Quoted from Scoot:

LED kit will not damage a game per say, but unscrewing a GI bulb socket and shorting it to something metal on the playfield most definitely will damage something. When changing wedges to led, I always have the game on. But with the GI unscrewing from the bottom of the playfield, should be done with the game off. I too have learned the hard way...

I did all of the gi bulbs from the top, the game needed a good cleaning anyway, but what you said got me thinking, and you know what? I had to unscrew a couple of the gi bulbs from the bottom to get the subway track out, one of those could have easily touched something.

#10 8 months ago

I would definitely check all the bulbs and switches related to the sewer / fridge, since you said hell broke loose when you hit the sewer.. It sounds like the short happened when you hit that switch because otherwise hell should have broken loose on ball 1. Make sure no bulb sockets are touching nearby switches..

I'm a bit confused by your explanations. You say with the coil unplugged, the switches problem goes away, but then you said you unplugged the column / row connectors and the problem persists? If you are in the switch test with the column and row unplugged and you see a row full of closed switches, there's definitely an issue on the CPU board. If it only closes when you plug the connectors in, then that row wire is shorted somewhere.

#11 8 months ago
Quoted from Roamin:

I would definitely check all the bulbs and switches related to the sewer / fridge, since you said hell broke loose when you hit the sewer.. It sounds like the short happened when you hit that switch because otherwise hell should have broken loose on ball 1. Make sure no bulb sockets are touching nearby switches..
I'm a bit confused by your explanations. You say with the coil unplugged, the switches problem goes away, but then you said you unplugged the column / row connectors and the problem persists? If you are in the switch test with the column and row unplugged and you see a row full of closed switches, there's definitely an issue on the CPU board. If it only closes when you plug the connectors in, then that row wire is shorted somewhere.

Let me clarify. On our junkyard there is a molex plug right by the fridge coil, not sure if that's like that from factory or if it was added by us for some reason. When that plug is unplugged, I do not have the problems with the switches shorting out, when I plug it back in it starts freaking out. Separate from that, when I unplug the switch rows and columns from the cpu board, I get the same reaction, which leads me to believe my problem is on the boards and not coming from a short in the playfield wiring.

#12 8 months ago

Hey everyone, swapped U20 and that took care of all my switch problems, thanks to those that chimed in!

#13 8 months ago

Sounds like you shorted high voltage to U20, very common issue if a coil lug touches a switch connection. Glad it's fixed.

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