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(Topic ID: 100968)

Need Help - WPC-89 CPU not booting

By hiho

9 years ago

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9 posts
4 Pinsiders participating
Latest reply 9 years ago by hiho
Topic is favorited by 1 Pinsider

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#1 9 years ago

HIH

Ok, heres one I haven't seen before - a WPC-89 CPU that isn't willing to boot and displays continuously lit D21 (5v, ok) AND continuously lit D20 (Diag). Blanking D19 NEVER comes on. The board has been hacked around that area (u5, u21) but I measured continuity from the IC's and, while not looking pretty, continuity seems to be good. Also measured continuity on data lines A0-A15, D0-D7. Also tried multiple known-working game roms. Also tried different 68b09 and ASIC.

Lacking a logic probe, is there anything I can do at that stage? I didn't really find anything documented at for that condidtion.

Cheers,
Georg

#2 9 years ago

MAT

The_Director

Carolina Pinball Repair

11y 94,450 3,769 9 2

Have you tried booting with just the power cable run over from the power drive board with no switch matrix or ribbon cables plugged in? If it boots properly with just the power line, then you can eventually isolate what connected board might be dragging it down.

#3 9 years ago

HIH

hiho

Pinside member

Elsarn

10y 41,050 58 7

Yep, forgot to mention - CPU is already isolated with only the power connector being connected.

#4 9 years ago

HIH

hiho

Pinside member

Elsarn

10y 41,050 58 7

Bump. Any ideas welcome.

#5 9 years ago

JWJ

johnwartjr

That Pinball Place

Columbus, IN

12y 77,400 6,479 14

One thing that's worth looking at - how is the CPU jumpered?

If it's a board that was originally in a FH or BOP, it's possible that it's jumpered incorrectly for the newer games. This is a good first thing to check

http://thatpinballplace.com/documents/rejumpering_wpc_cpu.htm

No luck there? Get the logic probe. Check the data and address lines, and see if they are running. Check them at a few places on the board. ROM, RAM, Processor, the chips that have been socketed.

You could also try the test listed here on the various 74xx chips on the CPU:

http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit

It's not a silver bullet, but it has helped me find a few bad ones.

1 week later

#6 9 years ago

HIH

hiho

Pinside member

Elsarn

10y 41,050 58 7

Thanks for that - CPU jumpering is OK. I identified one more bad 74xx IC, U14 - but that didn't change anything.

Got myself an oscilloscope. The board shows no clock signal at U9 and U5. I'm also getting nothing on U9 Pin 37 (reset pin), which should be high but always stays low.

I suspect my next culprit is U10?

Cheers
Georg

#7 9 years ago

HIH

hiho

Pinside member

Elsarn

10y 41,050 58 7

Bump!

#8 9 years ago

DOC

doctor_pinball

Doctor Pinball

Bucharest

11y 54,150 557 57 34

RAM is an easy fail so swap ram 6264 first !

#9 9 years ago

HIH

hiho

Pinside member

Elsarn

10y 41,050 58 7

ok, I ordered a bunch of these. cheers

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