(Topic ID: 196900)

Tech: WPC-95 CPU

By DocRotCod

6 years ago


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  • 20 posts
  • 7 Pinsiders participating
  • Latest reply 6 years ago by noflip95
  • Topic is favorited by 4 Pinsiders

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#1 6 years ago

So picked up an NBA Jam recently and I had no video/audio. I tracked down issue to CPU board. Game boots up and plays, just no audio/video. Put in CPU board from my Totan and everything works perfectly.

Upon further examination on the 'bad' CPU board, the battery holder has been removed and u1, u2, u3, and u5 have been replaced. I also tested ASIC, CPU, Game ROM, Security chip, and RAM.

There was some minor battery damage (yes I know it can be misleading how bad it really is). I replaced and socketed u5 and there was some corrosion on the legs, and I repaired a trace next to the chip.

Overall the board looks great, just can't figure out what to look for now. u1, u2, and u3 were replaced as per the schematics it looked like those directly affected the I/o and audio connector.

I'm competent with testing, troubleshooting, soldering, etc. so if someone would like to assist me I am up to the challenge.

Thanks!

#2 6 years ago

On the bad CPU are the connector pins in good shape?Might need to reflow some solder on those header pins

#3 6 years ago

What do the 3 leds do?

#4 6 years ago

The pins are in good shape. Re flowed them to be safe.

#5 6 years ago

The led lights are normal. Bottom light solid, blanking light blinking. Game comes up and lights go into attract mode. You can coin it up and start a game. All coils and flashers work. Just no sound or dmd. Led on a/v board does not light or flash.

Put in different CPU board all works normal.

#6 6 years ago
Quoted from DocRotCod:

The led lights are normal. Bottom light solid, blanking light blinking. Game comes up and lights go into attract mode. You can coin it up and start a game. All coils and flashers work. Just no sound or dmd. Led on a/v board does not light or flash.
Put in different CPU board all works normal.

Hmm that's an interesting one. Ribbon cable headers look good? Tarnished?

Otherwise I'd get out the multimeter and start testing for continuity on the traces. Some components need to make their board connection on the top. Check that where the damage was.

#7 6 years ago
Quoted from dudah:

Hmm that's an interesting one. Ribbon cable headers look good? Tarnished?
Otherwise I'd get out the multimeter and start testing for continuity on the traces. Some components need to make their board connection on the top. Check that where the damage was.

Pins look good. I'll start checking traces tomorrow. Luckily damage isn't too bad so hopefully i'll track it down quickly.

#8 6 years ago

Mind posting a picture of the board?

#9 6 years ago

Ok here are some pics. This shiny part is where the board was sealed when the battery pack was taken off.

IMG_0616 (resized).JPGIMG_0616 (resized).JPG

IMG_0617 (resized).JPGIMG_0617 (resized).JPG

IMG_0618 (resized).JPGIMG_0618 (resized).JPG

#10 6 years ago

From my pics I can see u25 and u27 have some corrosion.

#11 6 years ago

When you plugged the HV board in. Did you get a flicker...then slow blinking from the LED on the HV board? Or was it just out?

#12 6 years ago
Quoted from DocRotCod:

From my pics I can see u25 and u27 have some corrosion.

Left side of C60 and C61 look suspect also, but just could be the angle of the picture.

#13 6 years ago

Looking at the schematics..my best guess is someone tried to fix this probably by shotgunning the Audio and I/O side (U1, U2 and U3)

At this point I would start buzzing traces working backward from J202 and J201 trough those socketed IC. I bet you'll find a busted\lifted trace there. The stuff in the acid zone doesn't really pertain to the Audio and Sound

The good thing is MPU are terribly expensive if you have the ASIC and Security IC

EDIT: Parts of U5 are used by the Audio and a couple of the resisters there also (R120, 121, 124, 125)

Check these for starters:

J202 Pin 33 -> U5 Pin 4
J201 Pin 23 -> R125 -> U5 Pin 2
J201 Pin 25 -> R124 -> U5 Pin 6
U5 Pin 1 -> R120
U5 pin 5 -> R121

#14 6 years ago
Quoted from Monster_Bash:

Looking at the schematics..my best guess is someone tried to fix this probably by shotgunning the Audio and I/O side (U1, U2 and U3)
At this point I would start buzzing traces working backward from J202 and J201 trough those socketed IC. I bet you'll find a busted\lifted trace there. The stuff in the acid zone doesn't really pertain to the Audio and Sound
The good thing is MPU are terribly expensive if you have the ASIC and Security IC
EDIT: Parts of U5 are used by the Audio and a couple of the resisters there also (R120, 121, 124, 125)
Check these for starters:
J202 Pin 33 -> U5 Pin 4
J201 Pin 23 -> R125 -> U5 Pin 2
J201 Pin 25 -> R124 -> U5 Pin 6
U5 Pin 1 -> R120
U5 pin 5 -> R121

I checked all the pins and through the u1, u2, and u3, and in addition did the specific tests above and everything toned out.

#15 6 years ago
Quoted from DocRotCod:

I checked all the pins and through the u1, u2, and u3, and in addition did the specific tests above and everything toned out.

Time for the U25 and U27 to get replaced. For sure U25 would not cause this issue, but I'm curious of U27.

#16 6 years ago

I'd also replace the electrolytic caps while you're at it

#17 6 years ago
Quoted from PinballManiac40:

Time for the U25 and U27 to get replaced. For sure U25 would not cause this issue, but I'm curious of U27.

Replaced both of these, still unchanged.

#18 6 years ago

Ok maybe I found something. Per the schematics, on J201 I/O Extend my pins that are suspect go like this:

Pin 11 -> U2 Pin 18
Pin 13 -> U2 Pin 16
Pin 15 -> U2 Pin 3

Here how mine tones out:
Pin 11 -> U2 Pin 16
Pin 13 -> U2 Pin 3
Pin 15 -> U2 Pin 18

Is there an error in the schematics I'm looking at or have I found something?

Here are the schematics I am referencing:

http://arcarc.xmission.com/Pinball/PDF%20Pinball%20Misc/Williams%20WPC-95%20Schematics%20Manual.pdf

#19 6 years ago
Quoted from DocRotCod:

Is there an error in the schematics I'm looking at or have I found something?

How do these points compare to your TOTAN board?

#20 6 years ago
Quoted from DocRotCod:

Ok maybe I found something. Per the schematics, on J201 I/O Extend my pins that are suspect go like this:
Pin 11 -> U2 Pin 18
Pin 13 -> U2 Pin 16
Pin 15 -> U2 Pin 3
Here how mine tones out:
Pin 11 -> U2 Pin 16
Pin 13 -> U2 Pin 3
Pin 15 -> U2 Pin 18
Is there an error in the schematics I'm looking at or have I found something?
Here are the schematics I am referencing:
http://arcarc.xmission.com/Pinball/PDF%20Pinball%20Misc/Williams%20WPC-95%20Schematics%20Manual.pdf

Warning with the WPC-S and WPC-95 schematics : there is many errors inside

Some noticeable:

On WPC-S : if you look at the Security PIC connections, you can notice that the labels for the pins SW ROW/SW DIR on ASIC are inverted, fortunately the pin numbers are correct. This error has been corrected on the WPC-95 schematic.

On WPC-S, the data bus on U24 (74LS374) is not wired as mentionned: the nibbles D0..D3/D4..D7 are inverted ! Of course, the pin numbers are wrong but the bus is correctly connected to the CPU (D0 goes to D0 ). There is no error on WPC-95, as U24 has been replaced by a 74LS574, with a more friendly pins placement.

About J201 : YES, THERE IS ANOTHER ERROR HERE, not corrected on WPC-95 schematic.
Indeed, for J201 the correct pins connections are:

Pin 11 -> U2 Pin 16
Pin 13 -> U2 Pin 3
Pin 15 -> U2 Pin 18

I have checked this on a normal WPC-95 board and also on the WPC-95 prototype board. Both have the same wiring, so, the WPC-95 schematic has also errors here.

Surprisingly, the WPC-S schematic has no error at this point.
The U2 pin in/out is correct. A7 arrive on pin 4, A6 on pin 17, A5 on pin 2.
And of course... this is also wrong on the WPC-95 schematic (A7 on pin 2...)

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