(Topic ID: 148807)

NGG/WPC95 - A/V board Ghost in the Machine

By sd_tom

8 years ago



Topic Stats

  • 9 posts
  • 3 Pinsiders participating
  • Latest reply 8 years ago by sd_tom
  • Topic is favorited by 1 Pinsider

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#1 8 years ago

After the holidays and some travel (so long period off) I turned on NGG that had been working perfectly and it is doing all kinds of random stuff now.

Initially, the CPU board was diagnostic LED'ing a problem with the RAM (anypin DMD+ NVRAM) while simultaneously the audio board was beeping 3 beeps which is a sound ROM issue. Re seating all the connectors didn't do much.

Last night I got new NVRAM and new Sound Roms in and replaced them. Now i'm getting, repeatable at least, symptoms such as the follows:

- If the machine's been off long enough to discharge the caps (30 min or so), the game will come up correctly and DMD will be fine.
- After 30-90 seconds the DMD will start to get garbled; was perfect before that.
- Along with the progressive DMD deterioration, if i wait long enough, random solenoids will fire (like a flipper or something) very briefly.. almost like a ball search but it's not a ball search at all.. just similar random pulses.
- If I turn it on / off again it will just come up garbled vs start good

Any thoughts? I assume something is failing in the power system? Not even sure where to start with walking though weirdo power issues.

#2 8 years ago

I had similar weirdness with my NGG. Turned out to be ribbon cable related, which I'm in the process of replacing.

#3 8 years ago

I guess I will pull the av board at minimun and probably all the boards and look for cracked headers or anything else suspicious over the weekend. And check the ribbon cables.

Wish it was just the DMD acting funny as I could justify a colorDMD

#4 8 years ago
Quoted from NonStopSwagger:

I had similar weirdness with my NGG. Turned out to be ribbon cable related, which I'm in the process of replacing.

This is a good place to start, clearly you are getting incorrect data/addressing on the bus and a bad cable can certainly cause oddness. Once got a TZ that was in great physical shape but would not boot, got a great price on it, $1400 I think, swapped out the ribbon cables and the game was good to go.

#5 8 years ago

Yeah will look. There is something to the fact that it works when it starts cold though.

Also I am nervous as something seems to have taken out the eeprom and nvram as I am not getting any board errors now that I replaced them. Cosmic rays I guess.

#6 8 years ago
Quoted from sd_tom:

Also I am nervous as something seems to have taken out the eeprom and nvram as I am not getting any board errors now that I replaced them.

Unfortunately if you had some type of a short to the address/data bus it could do that, and also damage other chips associated with the bus.

#7 8 years ago

Where's the best / detailed board interconnect diagram? Is it with the game schematics (not home right now) or somewhat separate. I own a logic analyzer and oscilloscope but I am still a newbie at using them to diagnose things (a new secondary but related hobby for me).

#8 8 years ago

answering my own question here, WPC-95 Schematics here:
http://arcarc.xmission.com/Pinball/PDF%20Pinball%20Misc/Williams%20WPC-95%20Schematics%20Manual.pdf

I'm going in

#9 8 years ago

K so poking around and CPU board, has only between 1.2 kOhm and 3.2 kOhm between VCC and Ground (depending on DIP switches). Presuming that is too low / short somewhere.

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