(Topic ID: 225982)

WPC89 MPU on the bench (reset loop)

By arqpuebla

5 years ago


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  • 31 posts
  • 2 Pinsiders participating
  • Latest reply 5 years ago by Pin_Guy
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    #1 5 years ago

    Greetings great community. I.m having some problems debugging a WPC89 MPU.

    I.m feeding it on a bench with an external power supply, (that I have used it on lots of other mpus).
    The MPU boots perfectly, D19 lit, and go off and D20 start blinking, but after 30 secs or so, D20 goes off and D19 lit and go off and D20 start blinking, and so on and so on.

    What I have tried :

    Reseated ASIC (with a special tool)
    Changed ASIC from other working MPU
    Changed U4 from other working MPU
    Changed game Rom from other working MPU.
    Waited a few minutes, and tested with my fingers each IC on the board, and no one gets hot or warm.
    Voltage across C31 is 5,08V all the time.

    Any ideas what to try next? I got a logic probe.

    Thanx in advance.

    #2 5 years ago

    ...

    #4 5 years ago

    hmmmm I will measure c31 capacitance and ESR , just in case, and why not, just replace it, half of the time they have wrong values on my experience.

    #5 5 years ago

    wow 3450uf and 0,5 ESR , will replace it, and report back

    #6 5 years ago

    Good call, If this is the original (grey) capacitor I always replace them before I event test the board. Its a super easy and cheap replacement.

    #7 5 years ago

    Yes, Was the grey one, not blue.
    Just replace It,

    no luck

    Took it the time until it reboots itself, 10 secs between reboots .

    #8 5 years ago

    Pin_Guy what about a watchdog jumper wire. never did that, or need to do it. That will disable the watchdog.? and let's see what happens

    #9 5 years ago
    Quoted from arqpuebla:

    pin_guy what about a watchdog jumper wire. never did that, or need to do it. That will disable the watchdog.? and let's see what happens

    I've never done that either, but it looks like jumpering pin 1 to 3 will force the low needed to disable it at the ASIC. Are you seeing a low going BLANKING signal coming from U9-35?

    pasted_image (resized).pngpasted_image (resized).png
    #10 5 years ago

    u9/35 ? thats diag led. will check if it is low.

    #11 5 years ago

    No, I meant 34...are you actually seeing it change states?

    #12 5 years ago

    At U9 / 35 the logic probe alternate rapidly between low and high matching D20 led flickering, and when the MPU reset , (D19 stays on for 1 sec) the logic probe stay low when D19 is ON., and so on, and so on

    #13 5 years ago

    U9 / 34 (blanking) Starts low for 1 sec (D19 is on) then when D19 goes off and D20 start blinking, I got high reading and pulsing. Until it resets, and go LOW (D19 is on) etc...

    #14 5 years ago

    Ok, so you know the resets are coming from the ASIC. Are you seeing any changes out of the low voltage monitor U10?

    pasted_image (resized).pngpasted_image (resized).png
    #15 5 years ago

    never tested U10, how do I see changes? How do i test it?

    #16 5 years ago

    Should be able to check it with your logic probe. Low = Reset

    ASIC POR 61 input I assume POR = Power On Reset

    #17 5 years ago

    ok, on pin R (upper leg) or + (middle leg)?

    #18 5 years ago

    or maybe directly on U9/61

    #19 5 years ago
    Quoted from Pin_Guy:

    Should be able to check it with your logic probe. Low = Reset
    ASIC POR 61 input I assume POR = Power On Reset

    OK! I.-m going, and report back

    #20 5 years ago

    I prefer pictures

    pasted_image (resized).pngpasted_image (resized).png
    #21 5 years ago

    U10 / leg 1 (pictures!! ) and U9 /61 , stays HIGH and no pulsing all day long during the reset sequence.

    #22 5 years ago

    Hmmm....

    #23 5 years ago

    I suspect U5, I think I want to change it

    #24 5 years ago

    Socketed RAM or soldered?

    #25 5 years ago

    soldered.

    no problem, got soldering station and electric solder pump, give me few minutes. you vote for yes, change it?

    #26 5 years ago

    If it was socketed I would say to reseat it, soldered in not so much.

    #27 5 years ago

    If it was bad, you would be seeing RAM errors on the diag LED

    pasted_image (resized).pngpasted_image (resized).png
    #28 5 years ago

    OMG !!!!! problem solved, You mention "reseat", so I tought, will start reseating U8 (again). And why not, swap again with another RAM.

    and voilaa!!!!! no more problems!!!.

    #29 5 years ago

    NICE!

    #30 5 years ago

    will reflow that U8 , just in case. THANK YOU Pin_Guy for your time, and for doing WPC MPU therapy with me.

    #31 5 years ago

    Anytime, had a great time I love a good chin scratcher!

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