(Topic ID: 279523)

Twilight Zone DMD problem - corrupt ROM?

By adeysolaris

1 year ago


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  • 26 posts
  • 8 Pinsiders participating
  • Latest reply 1 year ago by ChrisHibler
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    #1 1 year ago

    This is a recent purchase with some issues. I replaced all playfield bulbs with LED
    Power mini playfield was dead - tracked down to blown fuses
    Clock works with the exception of one OPTO has failed - will replace that; the bulbs replaced by LED

    There has always been intermittent lost lines on the DMD and very slow to update, so I replaced both leads. The DMD driver is a new looking XPin.
    The new leads have not resolved the problem, in fact things have worsened as the pictures will show, the animations occasionally do play but they are soon frozen when they do

    Sound and everything works fine

    I have no other machines I can swop out parts with to test them

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    #2 1 year ago

    If you haven't done so. Please reseat ribbon cables from CPU to DMD Driver board to DMD. Both ends.

    LTG : )

    #3 1 year ago

    Display test threw up a load of paging errors...

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    #4 1 year ago

    Well there you go. RAM error.
    Remove, socket, replace.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    http://www.PinWiki.com/ - The new place for pinball repair info

    #5 1 year ago
    Quoted from LTG:

    If you haven't done so. Please reseat ribbon cables from CPU to DMD Driver board to DMD. Both ends.

    Believe it or not, I have seen this ribbon cable cause page errors and same missing lines before. Reseat it a couple of times at each board connection. When the lines are missing every 8th column, page errors happen. When every 8th column is stuck on, no page error happens. Either way, I seen the ribbon cable connections many times cause the problem. Not always, but most times. 2019-02-02 14_20_45-WPC ribbon cable to reseat - Paint (resized).png

    #6 1 year ago

    I've had a similar experience with the ribbon cable connector (data lines).

    I was asked to look at a DMC (dot matrix controller) exhibiting page errors. Sure enough display test shows page errors. I took the board home.

    Put the board on my bench. Passes display test perfectly. Weird. Put the board in a machine and it passes the display test perfectly. Put the board back on my bench. Passes display test perfectly.

    So I give the board back to the owner and well ... it works perfectly.

    I call it "pinball voodoo".

    #7 1 year ago

    The ribbon cables are new but the fault persists - so I am guessing the cable headers maybe a loose solder joint?

    #8 1 year ago

    If you have re-seated the ribbon cable and you know it's good (likely is but is not guaranteed to be due to being brand new) then take Chris Hibler's advice. It is very likely you have a problem in the digital logic section of the DMC board. If after replacing the SRAM the page errors still persist visit the Pinwiki page for WPC and you will find some more information on DMC page errors.

    #9 1 year ago
    Quoted from adeysolaris:

    The ribbon cables are new

    You know that because you replaced the one I am referring to in the picture?

    #10 1 year ago

    I really like confirming a board is at fault by putting the suspect board in a known working game.

    #11 1 year ago
    Quoted from PinballManiac40:

    I really like confirming a board is at fault by putting the suspect board in a known working game.

    Good advice if the potential problem is in the digital logic section (as it is for this problem). I concur that you should try this if you want another data point.

    For other higher voltage problems it can pose a risk of damage to the machine that is being used for testing. It's often safe but not always safe.

    #12 1 year ago

    I took the CPU board out - took photos and gave it a clean with a brush. It looks in very good condition.
    20201016_112033 (resized).jpg

    20201016_112055 (resized).jpg
    Problem with the RAM seems to make sense, I don't see how a faulty ribbon cable would lead to a report of a RAM error in the Test utility...?
    Now
    I am assuming the RAM chip is this one (number 2)
    CPU board (resized).jpg

    #13 1 year ago

    Number 1 is the ram. 2 is the game rom and 3 is the cpu

    #14 1 year ago

    The RAM being talked about, referred to several times, is on the DMD controller board, not the MPU.

    Since you have the MPU out, press on all the sockets ICs, just as I had previously mentioned. You will hear a lot of crunching as you press on them.

    This is the DMD controller board.

    pasted_image (resized).png
    #15 1 year ago

    A seeming RAM error can be reported because the MPU board couldn’t accurately communicate with the RAM. This can be caused by the MPU, ribbons, or the dot controller logic. But most often, the RAM is the cause.

    Not knowing which Board the RAM is on leads me to believe you should send the board to a pro.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    http://www.PinWiki.com/ - The new place for pinball repair info

    #16 1 year ago

    I have no idea about the ram, but I've had the ribbon cables themselves go bad as well. Swaped the cable with STTNG, ordered a new one and all the problems went away. My poor TZ is so old...

    #17 1 year ago

    I’m in the US but my advice is to send the MPU and the dot controller at the same time. Install NVRAM on the MPU and get rid of those batteries. Use the 6264 RAM on the MPU to (socket first) replace the RAM on the dot controller.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    http://www.PinWiki.com/ - The new place for pinball repair info

    #18 1 year ago

    The DMD controller is X pin
    someone from X Pin read my post and showed me how to run a diagnostic of their controller - which brought up the DMD working perfectly
    So I think we can discount the dot matrix controller (unless the ribbon socket has a problem?)
    Also I am in the UK so sending to the States (well - I am not against it) but I seem to recall that I still have to pay duty on these items incoming

    #19 1 year ago

    Okay here is what I gather from the feedback (thanks to everyone so far)

    I need an (AnyPin) NVRAM anyway, to avoid the risk of leaking batteries
    and it may solve the problem if it is the RAM chip on the processing board

    #20 1 year ago
    Quoted from adeysolaris:

    I need an AnyPin NVRAM anyway

    AnyDMD+ NVRAM is better in this case and cheaper. The AnyPin has switches on it that would not serve any purpose once it is set, unless you plan to use it to troubleshoot older games, which use 5101.

    Never seen the MPU RAM cause this issue to the DMD.

    Again, press on the IC's that are in IC sockets. Only takes one data line to have an issue.

    #21 1 year ago

    If re-seating the ribbon cables does not help, quite often the problem is with the U28 data bus buffer (74LS245) on display controller board.

    #22 1 year ago
    Quoted from Tuukka:

    If re-seating the ribbon cables does not help, quite often the problem is with the U28 data bus buffer (74LS245) on display controller board.

    Not in this case since it is not an OEM board.

    Quoted from adeysolaris:

    The DMD controller is X pin

    #23 1 year ago

    Fault located. something was wrong between the IDC header and the logic in the DMD board. I found slight pressure on the board caused the problem to disappear - it is a weird one - maybe weak traces or solder

    #24 1 year ago

    Dicey solder joint. Glad you found it.
    I still advise replacing the RAM on the MPU with NVRAM.

    Chris Hibler - CARGPB #31
    Http://chrishiblerpinball.com/contact
    http://www.PinWiki.com/ - The new place for pinball repair info

    1 week later
    #25 1 year ago

    Thank you Chris - I will need to find someone in the UK to do that job - can you recommend anyone?

    #26 1 year ago
    Quoted from adeysolaris:

    Thank you Chris - I will need to find someone in the UK to do that job - can you recommend anyone?

    My network of known good techs doesn't extend across the pond.
    However, I'm always up for a trip. I promise to keep my expense report as reasonable as possible.
    --
    Chris Hibler - CARGPB #31
    http://www.ChrisHiblerPinball.com/Contact ... for board repairs
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

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