DMD Repair Anyone?

Started 2 years ago by bgrom8 in forum TechTech: Generic.


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DMD Repair Anyone?


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  • Started 2 years ago by bgrom8
  • 12 Pinsiders participating in this thread.
  • Latest reply from Crash

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    2 years, 9 months ago
    #

    I just got a Striker Xtreme with a DMD that works for the most part. The only thing is that it has a couple vertical lines out. Does anyone know how to fix this? Thanks!


    2 years, 9 months ago
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    I have a Friend that HAS drilled thru the Glass and did the Repair. He had 1 line out. I think it was a Vershay DMD.. I've tried,, I didn't have the right drill bit.. but,, it can be done.


    2 years, 9 months ago
    #

    Try this make sure the machine is off and locate the dot matrix board and
    there is a ribbon cable going from the board to the dmd display just reseat
    that cable ribbon from the board.Take out a little bit and put back in.If that
    doesnt work then it could be broken traces on the DMD.


    2 years, 9 months ago
    #

    i had a few lines out on a dmd. think it was a vishay? fixed it fine too.

    just look at the very back of the dmd and check small connections for each line of the dmd. the chances are the outed dmd lines have lost their connection to the controller board, hence they're dead. I simply soldered a bit of wire round the outside of the glass dmd to each faulty line and, hey presto, it bought the dead lines back to life. it's a bit fiddly as each connection is fairly minute. plus, it could be called a bodge job, but it saved me replacing what was essentially a good dmd.

    early vishays have this problem because the connections are too stressed bending round the back of the dmd (i think?). it's mentioned in clays repair guides.

    or, just buy a new dmd


    2 years, 9 months ago
    #
    juleshoddy said:

    i had a few lines out on a dmd. think it was a vishay? fixed it fine too.

    just look at the very back of the dmd and check small connections for each line of the dmd. the chances are the outed dmd lines have lost their connection to the controller board, hence they're dead. I simply soldered a bit of wire round the outside of the glass dmd to each faulty line and, hey presto, it bought the dead lines back to life. it's a bit fiddly as each connection is fairly minute. plus, it could be called a bodge job, but it saved me replacing what was essentially a good dmd.

    early vishays have this problem because the connections are too stressed bending round the back of the dmd (i think?). it's mentioned in clays repair guides.

    or, just buy a new dmd [:-)]

    They lose their connections from vibration from the speakers.Theres a way
    to fix it with epoxy glue but be careful if you are planning on soldering those
    traces are close together.


    2 years, 9 months ago
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    Thanks guys i'll give these a shot


    2 years, 9 months ago
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    pinmike said:

    They lose their connections from vibration from the speakers.Theres a way
    to fix it with epoxy glue but be careful if you are planning on soldering those
    traces are close together.

    To calrify Mikes point a bit you need to use a *conductive* epoxy or paint. Plain ol' clear two part epoxy is an insulator and will defeat your objective.

    I've fixed DMD's with ribbon type connectors using copper window defroster paint available at your local auto arts store *cheap*. The copper paint itself has very little mechanical strength so after I test that all is working I then put a few drops of super glue on the repair to give it some rigidity.

    Others recommend silver bearing conductive glue. This is VERY expensive and is intended for electronic prototypers for quickly adding or modding traces on circuit boards. It does the same thing as the cheaper copper paint but is overkill in my opinion. It also has no mechanical strength and would pop off again easily if not glued down.

    As for drilling, I admire whomever was able to pull this off. Number one, you would need a diamond coated drill bit to cut the glass. Number two, you risk outgassing the plasma wich wold immediately destroy the display and number three, you risk cracking the glass. I have had some luck chipping the edge of the glass away with a carbide pointed metal scribe. I had to use my magnified headgear to do this and still had the same risks as mentioned above. I was unable to expose enough of the lead to solder but was able to use the copper paint to make the connection again.

    In the end, be prepared to buy a new DMD but certainly use the broken one as a learning tool!


    2 years, 6 months ago
    #

    I just managed to fix a DMD with 3 horizontal lines out. I had seen example posted elsewhere on the web of people drilling through the face of the glass to the point which the DMD pins connect with the board pins (which, in theory, are within a space separated from the actual "dot" space by epoxy lines that hold the glass together). It looked kind of risky and while I understood that the repair would generally not be visible, it did seem like the jumpers might interfere with the rubber baffle that keeps in light around the display.

    I assume that my circumstance is pretty common. When I checked the pins coming from the glass, the one with the lines out were broken right at the place where they enter the glass "sandwich" (i.e., there are embedded in the thin epoxy layer). It is important to check to pin numbering so that you don't get confused. The Babcock DMD in my Pinball Magic has the order 32 to 1 top to bottom and 128 to 1 left to right when viewed in place. Thus, if top line is out, you might be confused that when you have the DMD out for inspection, pin 1 seems perfectly solid; you need to check pin 32 instead.

    Anyway, I reasoned that there was less risk, drilling from the side along the path of the pin between the glass. I selected a Dremel diamond coated bit (7144) that was 3/32" max (the width of the pins apart) but tapered such that, given the distance in I planned to drill, the holes for pins next to each other would still be separated enough. I actually found that using a regular cordless drill to be about as effective as using the High Speed Dremel motor - certainly far easier to control when getting started.

    Even though you are drilling from the side, it still important to protect the face of the glass from any slips. You will also want to gently bend the broken lead down the board and out of the way. Also I would start the hole just slightly above the epoxy line rather than right on it. The diamond coated bit chews through glass and epoxy fine but it not the best against the metal of the embedded pin. But in someways that is ok in that if the bit kind of goes in on top of the pin, you'll end up with more metal surface area to bond to. So when looking at the face of the DMD, you can clearly see how far the bit has gotten: there will be a white line coming from the edge through the dark of the epoxy. It is good to look from this view while drilling to make you are going along the path of the pin toward the connection within the glass. Though a little trial and error it seems like going about 3/4ths of the way through the epoxy line works pretty well - there's more space to fill with solder. In any case, you need to be patient as it does take a while to get to where you want to be.

    Once the holes are done and blown clean, I secured the display on its edge I melted some silver solder paste (this is cheap as opposed to the epoxy) into the holes, and then also melted some regular solder into them. I did find that it seemed to improve the likelihood of getting the final bond solid to drill out the soldered holes again, perhaps by pushing solder into the roughened glass surface. But regardless, I first got solder into the holes and then I got some stiff wire of the type used for component leads (I cut mine off and old capacitor) and heated it with the iron while pressing on the solder in the hole until it slid in the length of the hole. It may take more than one attempt but with a little persistence, you'll get your new lead(s) in there nice and solid.

    Once the solder is nice and solid, you should go test the connection. Touch a jumper from the bent down broken lead to the new lead and hopefully your line/column is back in business (if not, try again but I will say that every time I got a solid new lead in place it worked). If all is okay, you can bend the old lead back up into place and trim and bend the new lead down toward the board. The new lead length should take the end to the surface of the board so that you can solder the two of them together further from the glass to not risk softening that connection.

    I think this process might get unwieldy if you had several lines/columns in a row to fix but I did manage with two right next to each other.

    Finally I will say that I did a couple of other simple things that *might* help to prevent future breaks. As per Cliffy's suggestion, I added dabs of super glue to to point where the pins enters the glass for every pin (it didn't take all that long to do all 160). Second, I added thin but flexible spacers between the plastic posts that attach the DMD to the front panel which (only theorized) might dampen some of the higher frequency vibrations coming from speakers, etc.


    2 years, 6 months ago
    #

    One other thing: seems like the DMD was supposed to be attached by six posts, four on the corners and two in the middle. It looks like the middle two were never installed in my machine's case. The pins that cracked on my board were nearest the posts where the board is taking the most stress of the mounting. One wonders if but for the addition of two more 12 cent parts, the $150 DMD would be less vulnerable to these problems...


    2 years, 6 months ago
    #

    I used the silver conductive epoxy as recommended in pinrepair on mine and it works fine now.
    Was $35 for the kit.
    I think the copper epoxy used to fix car window defrosters would work. It is much cheaper.


    2 years, 6 months ago
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    I had a DMD that worked fine except one 3 in verticle line. I replaced the dot matrix board, worked fine after that.


    1 year, 6 months ago
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    Sorry to bump this, but could someone explain where to run the jumper? I would like to try this but will not drill the glass. If I have to live with one line being out I will though.


    1 year, 6 months ago
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    Yes a lot of good information here. The drilling is not for me b


    1 year, 6 months ago
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    I see how the ribbon cable is attached now... hopefully it's not the connection in the glass.


    1 year, 6 months ago
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    If you search back a page or two you'll find my thread where i repaired four broken traces, pictures included. Im on my phone so i cant post a link. "DMD repair worked out." good luck, if you have broken traces to the glass its not an easy repair but can be and has been done by a few people.


    1 year, 6 months ago
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    Thanks for pointing that out, figured it what something along the lines of that.


    1 year, 6 months ago
    #

    Sometimes it's just cheaper to buy a new one.


    1 year, 6 months ago
    #

    Cheaper? Last I checked conductive windshield defroster and jumper wire doesn't cost $140.



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