(Topic ID: 322718)

WPC-95 (Scared Stiff) Power Problems At Boot

By D-Piddy

6 months ago

Topic Stats

  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 3 months ago by D-Piddy
  • Topic is favorited by 1 Pinsider


Linked Games

#1 6 months ago

I have been trouble shooting this by reading posts here and on PinWiki, but am running into a dead end. If I should post this somewhere else my apologies.

Here is what I am experiencing:

-I found discontinuity between the 5 big caps at C9 on the power/driver board (PDB). When I removed it, I found that the trace had been repaired previously. I rebuilt the trace and now have continuity between the caps. However, the problem persists.

-I have good voltage on all the test points, even though LED 02 is not lit.

-Coils, GI, and Lamp Matrix are affected in both the playfield and backbox.

-I have reseated all plugs on PDB, including the ribbon cable between the CPU/MPU board. I also wiggled the ASIC. Things on that board look good.

-I am not experiencing resets or weird artifacts on the DMD. I get the bong at boot up and an instant credit dot when it cannot initiate the spider. That is the only item on the error report - “Wheel Error.”

If I let it go long enough it will eventually even out and play just fine. I can even complete the wheel test in the service menu and clear the credit dot and then the spider works fine too. If it is working fine and I turn the game off and back on quickly it will still work fine. If I leave it off for more than half an hour it will go back to this unless I leave it on long enough to even out again.

I have tested just about every diode on the board against each other, of the same type of course, and am getting comparable reading readings on them.

Should I apply power on my bench and check the processors with a logic probe? Start pulling diodes off the board to test them that way? I want to check the other large caps, but am reluctant to take them off unless I absolutely have to.

The fact that it appears to “warm up” leads me to think that I still might have a cap issue though. Especially since the time the machine is off will dictate how long it does this flickering before evening out.

Really just looking for thoughts and or direction on what to check next. Thanks in advance for any ideas.


#2 6 months ago
Quoted from D-Piddy:

I found discontinuity between the 5 big caps

Through hole plating messed up ?

LTG : )

#3 6 months ago

It may be time to replace those caps on the power board

#4 6 months ago
Quoted from LTG:

Through hole plating messed up ?
LTG : )

Thanks, Lloyd. The through hole looked good on C9, the trace repair was for the trace that runs under the cap.

I haven’t pulled the other big caps yet. I see one more that had obvious repairs, but continuity goes all the way through those caps now. My thinking was that would have covered the plating, but admit I could be wrong in that thinking.

I should probably just ease those caps off, make sure nothing isn’t obviously damaged, and test the caps once they are off the board.

#5 6 months ago
Quoted from Purplecheesemonk:

It may be time to replace those caps on the power board

Thanks, I agree that may be it. I think that taking those off and testing them all and checking the traces is my next stop.

2 months later
#6 3 months ago

Just to close the loop on this.

It ended up being the CPU board. I suspect unneutralized acid damage. The batteries were removed in 2017 and NVRAM installed, but there are components in that circuit with corrosion that must have still been active.

Replaced with a PinLED board and it fired right up. I hope to send out my original boards to have them serviced so I have functional spares.

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