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Switches on column 4 fire all other switches on column 4

No I don't think so, the game would just show it as a closed switch but it does sound suspiciously like something in that area is intermittently shorting, possibly when the pops fire. Have you checked the full range of movement of the pops from underneath (game off)?
 
Ped said:
No I don't think so, the game would just show it as a closed switch but it does sound suspiciously like something in that area is intermittently shorting, possibly when the pops fire. Have you checked the full range of movement of the pops from underneath (game off)?
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Yeah I've looked at that area so many times.

I removed two of the pops to investigate but saw nothing untoward, and that was before u20 went earlier today.

It really seemed like the bottom pop getting stuck on caused the issue. Nothing else noticeable happened, I'm stumped.
 
Try putting the game on switch test the thump various areasof the playfield to see if vibration is activating the switch matrix.
 
So thinking this through, if it was a coil power shorting to the switch matrix then it would certainly blow the U20, but would probably also blow the switch matrix power fuse on the driver board. If the pop was mechanically stuck (rather than the coil being being energised) then the switch would be closed but that wouldn't harm the switch matrix, it would just see it as closed and ignore it.
It works when you replace the U20, so its unlikely that anything else on the CPU board is broken

It could be a short from the GI to the switch matrix - can happen if a light socket is touching a switch somewhere (or touches occasionally when the pops activate), then this could also blow the U20

Take a closer look at the wires coming from the GI light in the pop bumpers - any chafing against the switch, missing insulation etc?

Edit : @Moonraker said this on Friday, I should have read the previous responses!
 
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It went again yesterday...
I am stumped, I have looked time and time again for any GI close to the switch wires and found nothing 😔

Got 6 chips left....
Other than looking again is there any other way to assist with diagnosing it?
 
Leftfield suggestion here - get someone else to look at it, and I don't necessarily mean a pinhead, or even anyone who has a clue about electrics. Just a fresh pair of eyes to look at the things you've already checked numerous times, who's happy to ask daft questions (like 'should that really go there?'). Dunno if there's a Mrs David_Vi, but that could be a good place to start. Just an idea (& maybe not a good one, I'll let you decide ;))
 
Silly question perhaps but have you checked all the switches in column 4 for possible shorts, not just the ones in the pop bumper area? the fact that you were working there may be just a coincidence
 
Judderman said:
Leftfield suggestion here - get someone else to look at it, and I don't necessarily mean a pinhead, or even anyone who has a clue about electrics. Just a fresh pair of eyes to look at the things you've already checked numerous times, who's happy to ask daft questions (like 'should that really go there?'). Dunno if there's a Mrs David_Vi, but that could be a good place to start. Just an idea (& maybe not a good one, I'll let you decide ;))
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Just me here atm unfortunately! And lockdown has made it a lot harder to get people to take a look.

Ped said:
Silly question perhaps but have you checked all the switches in column 4 for possible shorts, not just the ones in the pop bumper area? the fact that you were working there may be just a coincidence
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I've had a similar thought already and have looked about but nothing of note.
I've tried shaking the machine and all sorts to try and make it blow.
It seems to happen out of nowhere!
 
I played a game with the glass off as I was testing if the canon was level enough , was a real good game...
Then I noticed.

U20 gone again 😔 I am at a loss.
I tried to replicate it by playing a good game with ball in hand, put it all the places it can end up, touched it against switches... Shook the machine.

How do I eliminate it being a short? Could it be the board still?
Was it a coincidence I was playing a good game and sunk some ships? (I did replicate it and didn't get a new chip to blow).
 
David - I think if it was a board it would not last as long as it lasts before taking out the U20

I would suggest something under the playfield touching, maybe even a couple of strands of wire.

I just looked at the start of your thread and found that you adjusted the pop bumpers, so I would wire up a bright light and have a good look under those positions initially and work out from them. It sounds like a flasher/solenoid wire is near a switch matrix. Do this with the game off. Do not be afraid to wiggle a few wires to make sure the connections are good.

Have you had the machine long? If you have not then it may of been sold with this fault, you do not know.

I would also check GI lamp holders. Basically anywhere there is a solder connection.

This is one of those faults I could find in 10 minutes or 10 hours !

(Legally) as I run a pinball repair business I could come and (hopefully) repair, but with a 3 hour / 175 miles drive it wont be cheap. I would suggest finding someone more local (or bringing it to me if you wanted me to look at it).
 
Pick Holder said:
David - I think if it was a board it would not last as long as it lasts before taking out the U20

I would suggest something under the playfield touching, maybe even a couple of strands of wire.

I just looked at the start of your thread and found that you adjusted the pop bumpers, so I would wire up a bright light and have a good look under those positions initially and work out from them. It sounds like a flasher/solenoid wire is near a switch matrix. Do this with the game off. Do not be afraid to wiggle a few wires to make sure the connections are good.

Have you had the machine long? If you have not then it may of been sold with this fault, you do not know.

I would also check GI lamp holders. Basically anywhere there is a solder connection.

This is one of those faults I could find in 10 minutes or 10 hours !

(Legally) as I run a pinball repair business I could come and (hopefully) repair, but with a 3 hour / 175 miles drive it wont be cheap. I would suggest finding someone more local (or bringing it to me if you wanted me to look at it).
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So it can't be a board issue at all? It just appears so random considering you can play it for a couple days before it happens. The most frustrating thing is there's no fanfare when it happens (I only notice when I hit a target or the pops and notice they aren't working, and I don't get to the pops that often). It would be wonderful if I could see when it happens, at least I'd get an idea of where the problem might be.
Makes it so difficult to find the issue!

I did think I could unplug the GI for a couple days and see if I can narrow it down to being the solenoids as you can't really play with them deactivated.

I only noticed the issue since adjusting the pops and having the driver board repaired (capacitor had leaked).
So i don't believe the problem was there before.

I do have some local options that I'll look into.
 
Also, it's a good idea to check the top of the playfield as well as underneath - GI lamp holder close to a switch that potentially gets knocked by a pinball and touches momentarily? ramp switches in column 4 close to GI anywhere?
 
Just to eliminate something... The only other thing i did around the time of pop bumper fiddling was change the rom to a newer version. That couldn't cause issues could it?

I've played a bit tonight with the GI unplugged and no issues yet. But usually takes a few days to happen.
Been some really violent games too.

MajesticPinball said:
No doubt you'll rope me into looking into this on Friday then? 😂
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For Peshwari naan?
 
I am sorry!

It seems its fixed now, probably a coincidence that it hasn't happened since @MajesticPinball came over a month or so ago... He fiddled with something that appeared unrelated (a lamp socket near some switches, which I swear wasn't on the same column as was blowing, so I'd have never noticed)... And it hasn't died since!
 
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David_Vi said:
I am sorry!

It seems its fixed now, probably a coincidence that it hasn't happened since @MajesticPinball came over a month or so ago... He fiddled with something that appeared unrelated (a lamp socket near some switches, which I swear wasn't on the same column as was blowing, so I'd have never noticed)... And it hasn't died since!
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Mate you are so useless, the lamp socket was touching a bank of switches that was in the collum of the matrix that was part of the issue. Thanks for having faith in me mate 😂
 
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