You're currently viewing posts by Pinsider barakandl.
Click here to go back to viewing the entire thread.
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
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.
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.
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.
You're currently viewing posts by Pinsider barakandl.
Click here to go back to viewing the entire thread.
Wanna join the discussion? Please sign in to reply to this topic.
Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!
This page was printed from https://pinside.com/pinball/forum/topic/wpc-98-cap-id-please?tu=barakandl and we tried optimising it for printing. Some page elements may have been deliberately hidden.
Scan the QR code on the left to jump to the URL this document was printed from.
Forest Hill, MD