(Topic ID: 287358)

WPC-98 Cap ID please

By darowla

10 months ago


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  • 15 posts
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  • Latest reply 8 months ago by G-P-E
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#4 10 months ago
Quoted from darowla:

thank you
Going thru that area, scoping also gave me crazy results and thought I would try and tidy that side up. Currently got a non-booting (two top and bottom LEDs on only) setup.

I built a wpc89 MPU without the RTC stuff installed and it ran fine, so these are not likely the cause of a total lock up

#9 9 months ago
Quoted from darowla:

thank you
Going thru that area, scoping also gave me crazy results.

Seems like the probes can crash out crystal oscillator circuits like these. Parasitic capacitance?

I am not sure if it is exists with this RTC but usually look for an external clock on the CPU. It is a better place to check if the clock is working.

#11 9 months ago

In this case it is all external. With the CPU chips like a 6802 U21F gate is built into the CPU chip. Probe at U21 P12 for clock pulse would be a safe place. If you stick the probe around C29 and C30 is where you may crash out the crystal and it stops oscillating.

1 month later
#13 8 months ago
Quoted from darowla:

hi, ended up putting some replacement parts in that area, ended up with a different xtal that rated at 32.768 Khz but scope is now givinig a strage sine wave are 1.5Mhz... The over message said it is not critical so i will leave it for now.
My Boot doesn't happen, if I remove all chips the Top and Bottom lights remain the same, regardless of Watchdog.
My next goal is to tackle the ASIC, if I remove that I get 3 lights on start-up.
The Asic has had small amount of corrosion, I haven't considered it a 'right off yet'. I ordered a different socket as I seen pins not gripping very well so thats my next move.
This ASIC, I seen it for sale by some pinball repair sites, I presume its programmed or custom made in some way?
I been studying around the processor, seeing what it needs, I have now got some activity on the data/address lines, so I made some progress

The ASIC is a special, custom made chip but it does not need to be programmed. Hopefully it is just ASIC socket.

I would expect to see the 32 khz at U21 P12 like Pin_Guy posted above. Maybe check it again while you have the ASIC out of the board.

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