(Topic ID: 204481)

Help me identify a DMD problem

By Bsquared

3 years ago


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  • 15 posts
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  • Latest reply 3 years ago by j_m_
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    #1 3 years ago

    Bought a DMD clock awhile back and I absolutely love it, but the DMD has an issue.

    Basically I have a very faint vertical line that is always semi-lit (it's in the P in the photo). It's very hard to see and almost goes away if it's powered off long enough. I've done the test and no pixels are out, everything looks fine, and all the animations display OK.

    I'm sure you experts can help me to diagnose the issue!

    Thanks IMG_0143 (resized).JPGIMG_0143 (resized).JPG

    #2 3 years ago

    I assume this is an LED DMD and runs off of 5 or 12V. I think you are seeing a tiny gap in between the 8X8 (or 10x or 12x) led segments that is illuminated by light reflected from the inside of the panel. I think painting the gap with a sharpy or black paint will help minimize the issue.

    Of course you'd have to take the clock apart to do it.

    #3 3 years ago

    If that's one of the LED DMDs, then I've seen that before. I can't tell you what causes it. I've seen it mostly in new Stern games. The course of action was to get Stern to send a new DMD.
    --
    Chris Hibler - CARGPB #31
    http://www.ChrisHiblerPinball.com/Contact
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #4 3 years ago
    Quoted from Cheddar:

    I assume this is an LED DMD and runs off of 5 or 12V. I think you are seeing a tiny gap in between the 8X8 (or 10x or 12x) led segments that is illuminated by light reflected from the inside of the panel. I think painting the gap with a sharpy or black paint will help minimize the issue.
    Of course you'd have to take the clock apart to do it.

    That seems like it would be a relatively straightforward fix, but on close inspection it is actually a line of dots and not a blank space. If you look closely at the picture and count 3 dots over from the left side of the P in PM you'll see that it lines up.

    Quoted from ChrisHibler:

    If that's one of the LED DMDs, then I've seen that before. I can't tell you what causes it. I've seen it mostly in new Stern games. The course of action was to get Stern to send a new DMD.

    Hmmph, I suppose a new DMD will be in order if it gets really bad then.

    #5 3 years ago

    Look closely at the line. Is just one dot in the line not lit? If so, you can replace that square of leds and the line will go away.

    #6 3 years ago
    Quoted from CadillacMusic:

    Look closely at the line. Is just one dot in the line not lit? If so, you can replace that square of leds and the line will go away.

    Yes that looks to be the case. It's funny though because when hit the power switch (but leave it plugged in), that unlit dot lights up to full brightness. It also works fine during animations.

    #7 3 years ago

    Yeah, it's just a thing LED DMDs do. But the good news is a replacement square is like 9 bucks. The bad news is there's a lot of pins to unsolder, so get someone skilled to do it.

    #8 3 years ago

    just to add fuel to the fire (or information to help you out
    you'll need to contact stern for a replacement block. for some reason, they are using a different 8x8 block than what can be sourced from places like aliexpress (if you get one from somewhere other than stern, there's a 99% chance that the red will not be the same color

    you'll want to use something like a hakko FR300 desoldering gun to remove the block. there are a total of 16 pins on each block. additionally, you may or may not have to remove a minimum of 2 blocks if the offending 8x8 block is nestled in rows 2 or 3 due to the fact that they are tightly packed and hard to remove otherwise.

    when I've done this (I've repaired about 4-5 displays to date), I've used the face of another 8x8 block against the pins of the block that you're attempting to remove to push the desoldered block outwards evenly. getting the new one inserted can be a pain as well

    it's a shame that you don't live closer or I'd fix it for you

    #9 3 years ago
    Quoted from j_m_:

    ust to add fuel to the fire (or information to help you out
    you'll need to contact stern for a replacement block.

    Good to know as I have a DMD with a line out and haven't embarked on the repair. Call Chaz at support? In all the times I've worked with support Chaz makes it sound like they really don't sell directly and only ship parts when it is a warranty item. Is there someone else I should talk to or just call tech support?

    #10 3 years ago

    If its over 6 months old stern wont fix it, save your quarter. Just emailed them about 1

    #11 3 years ago
    Quoted from ccbiggsoo7:

    If its over 6 months old stern wont fix it, save your quarter.

    Oh yeah, it is over 6 mo. old, it is a Star Trek Pro from years ago. Soooo, what do we do?

    #12 3 years ago

    without derailing this topic too much...

    what I never understood is why stern didn't insist that during the manufacturing process (eg. when they wave pool soldered the 32 8x8 blocks), that they didn't use a jig or form to hold all of the blocks in place so that they went through the wave pool, they were all soldered nice and tightly together, all uniform and right next to one another instead of the gaps that are present on every single panel that I've seen

    #13 3 years ago

    If you talk to stern, make sure you read them any identifying info you have about the display. The colors can be deceptive."Amber" blocks look pretty darn red to me.

    As to why they didn't insist on a jig? Probably saved them $50. That's manufacturing for ya.

    #14 3 years ago

    FWIW I have seen no indication that the display in question is a Stern display. If this is a full sized DMD clock, then the LED display is a RGB display; have you tried changing colors? I run mine with the DIP switches set for Cyan and it looks fantastic.

    DSC00266 (resized).JPG

    #15 3 years ago

    Pin_Guy
    holy crap, you're right and I didn't even bother to notice that. I read the title of the thread, and read the issue but completely glossed over the fact that this was a clock and not a pinball display issue (I do sell a kit which uses the stern displays, but you're right

    it may be one of the clocks (which I do not sell) that only display in red and still use the 8x8 blocks (just those of a larger type than what a pinball dmd uses

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