(Topic ID: 251156)

Party Zone Row 2,3,4 ground short


By patrickvc

5 days ago



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  • 12 posts
  • 2 Pinsiders participating
  • Latest reply 1 day ago by patrickvc
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#1 5 days ago

I was working on a couple things on my PZ and after turning back on now I get this message on my dmd. After I disconnect the harness going to the mpu all the switches in the rows clear on row 2,3 and remove the cabinet switches harness it clears 4. When I activate any other switch when everything is hooked up the entire row shorts. Could the 2803a chip have gone bad? I checked every wire, switch, lamp. I can’t find anything touching

#3 5 days ago

I did and the entire row would activate when I would test. I changed the 2803 chip and got the ground short problems to go away but now I lost any registering on column 7. The ball troughs slings and a couple switches are out

#4 5 days ago

Which lm339 chip controls column 7 on a WPC mpu. I’m not seeing it in my manual

#5 4 days ago
Quoted from patrickvc:

Which lm339 chip controls column 7 on a WPC mpu. I’m not seeing it in my manual

none; the LM339s read the rows, your column pulses are generated by U20 (ULN2803A) this chip can be damaged by working on your machine with the power on. Just use the same matrix test procedure from pinwiki...and substitute column 7 (J206/207 pin 7) instead of the column 1 pulse at pin 1, if you have a logic probe (everyone should) then use that to determine if the column pulses are being generated.

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#6 4 days ago

Awesome thanks Pin Guy. I realized after reading a bunch I was wrong about the lm 339. Up the chain should be u14 as a possible culprit

#7 4 days ago
Quoted from patrickvc:

I did and the entire row would activate when I would test. I changed the 2803 chip and got the ground short problems to go away but now I lost any registering on column 7.

Quoted from patrickvc:

Up the chain should be u14 as a possible culprit

Please dont take this the wrong way as I don't know your board repair abilities, but it's more likely you damaged the thru hole at U20-13 than a failure of U14.

You can easily prove me wrong by measuring the resistance from U20-13 to J206-7. A reading <1 ohm is good, anything above that is not a good sign.
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#8 4 days ago

It was a socketed chip to begin with. I can see that u14 has already been changed by someone in the past. I will test just to make sure

#9 4 days ago

I just looked at the socket that had been replaced in the past and the hole for the chip looks questionable. I’ll pull the board tommorow and check points for continuity

#10 4 days ago

I really appreciate your help

#11 1 day ago

I have continuity between chip leg 13 and 206-6

#12 1 day ago

I changed the chip at u14. Everything is now working

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