(Topic ID: 220288)

WPC: U20 caught fire


By futurepinhead

1 year ago



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  • 15 posts
  • 9 Pinsiders participating
  • Latest reply 3 days ago by rotordave
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#1 1 year ago

My new Shadow has had more headaches than any other purchase to date ugh. But was playing a game and it reset. I turned it off and on and it sound Grounded Row 1. I pulled up the switch test and almost every switch was locked on. When I pulled out the MPU, U20 was in 4 separate pieces and was melted to the socket. I pulled the socket out and replaced it and a new U20 chip. I also noticed R72 was fried. So I followed R72 down to J207 and it was connected to Pin 6 which is Column 6 on the Switch matrix. I followed the wire to all the switches and I did not notice any loose wires on the switches or any nearby solenoids. I also looked at any solenoid tabs, GI tabs, and lots of other things.

Any other suggestions on what to look for?

#2 1 year ago

That’s pretty impressive!

What’s happened is some serious voltage has travelled up the switch matrix and blown your U20 chip to smithereens. Probably damaged the next one up the chain too.

Somewhere in the machine a coil, or a flasher, is touching a switch matrix wire. Or has worn though a wire.

So now you need to find it.

rd

#3 1 year ago

Don't see that one very often!

#4 1 year ago

I'd check the drop target assay. Seen this before on term 2 . The coil was worn through on the wrapper,unseen until removed. Additionally, the switch lug was grounded out on the drop target bracket.
One of these scenarios by itself is not an issue but both cause disaster.
Also take your meter and see if you have any voltage on your ramps, diverted etc. You could have a flasher,coil etc energizing metal components on the Pf.
An airball just right hitting a switch lug and energized ramp etc. Would cause this failure as well.
Sucks to have this issue esp.if intermittent.

Good luck.

#5 1 year ago
Quoted from pinballplusMN:

I'd check the drop target assay. Seen this before on term 2 . The coil was worn through on the wrapper,unseen until removed. Additionally, the switch lug was grounded out on the drop target bracket

I had a similar thing happen on Champion Pub.

The boxing bag mech in the top right corner is an issue ... the coil rotates with vibration, the lugs touch the metal bracket, bolts flow to the switch which is screwed to the bracket, booooooom goes U20 and at least one other chip.

These things can take a while to find, sometimes.

rd

#6 1 year ago

I should mention that there was a little bit of battery corrosion on the switch pins that I fixed previously this week.

I cant find any switches near any solenoids or flashers. I'm at a total loss on the cause.

I've replaced U18 and a couple resistors that were iffy.

Here is where I have the switch matrix now. When I hit any switch though, the switches light up completely randomly (example: 2 over here 1 over there 3 over hear all flickering very fast).
In the photo, the ones not in the 3 solid rows flicker like crazy the whole time.

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#7 1 year ago

It could have a 8 or 10 opto board under the pf that fried?
If you see the board under there you can unplug it to see if what remains plugged in works ok.
Or even try unplugging all the switches to the CPU, see how it acts.

#8 1 year ago

GOT IT!

So I replaced the 4514 long chip on the MPU and that got the switches all working again in the test. I still could not find the cause. The upper playfield was still not acting right and wasn't allowing me to move the armature. I moved it manually by hand and POW. This time the U20 didn't catch fire, but it definitely blew it. I flipped the mini playfield over and there was a little tiny scrape through the insulation on the coil that powers the armature. The resistor it fried doesn't correlate with the stripped wire, but that has to be it. I need to replace the optos that sense the ball in the upper playfield and I need to replace that U20 again and I hope this issue will be solved.

1 year later
#9 3 days ago

Funny ... after commenting on this thread a year ago, guess what just happened ...

A used Johnny Mnemonic I just landed just blew up in the most spectacular way. Smoke ahoy! Lol

rd

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#10 3 days ago

Hmmmmmm ... looks suspect. Lol

C7DCA8F6-CBEE-4C97-A5A0-C891775B173C (resized).jpeg

Loose Copper winding touches the metal second flipper switch which is right next to the coil ... coil fires ... boooooom goes the CPU.

rd

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#11 3 days ago

That was smoke, then pop!!

#12 3 days ago
Quoted from rotordave:

Hmmmmmm ... looks suspect. Lol
[quoted image]
Loose Copper winding touches the metal second flipper switch which is right next to the coil ... coil fires ... boooooom goes the CPU.
rd
[quoted image]

friggin' butchers!!

#13 3 days ago
Quoted from rotordave:

Hmmmmmm ... looks suspect. Lol
[quoted image]
Loose Copper winding touches the metal second flipper switch which is right next to the coil ... coil fires ... boooooom goes the CPU.
rd
[quoted image]

That’s funny. I had a similar experience. My u20 went out but did not melt. The guy I bought my Johnny broke the lug off the shooter coil and had the wire from coil hanging out and shorted on the second flipper (hand control) switch.

#14 3 days ago
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#15 3 days ago

Yep, burnt up the traces!

Stank out the house too!

rd

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