(Topic ID: 172023)

Dirty Harry - DMD Mystery

By dfsays

6 years ago

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  • 12 posts
  • 5 Pinsiders participating
  • Latest reply 6 years ago by dfsays
  • Topic is favorited by 1 Pinsider


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#1 6 years ago

I've been having trouble with my DH DMD and have exhausted all my options.

The photos show a couple examples of the issue.

Random rows on the DMD light up and images are often garbled or refreshing slowly.
The DMD also hums quite loudly, especially when I screen test the rows. Columns don't hum.

The backbox includes brand new boards for MPU, Power Driver, and DMD Controller and all have been tested to be working.
I've swapped all serial cables and the DMD with my Judge Dredd, and everything works fine over there.

The game "thumps" pretty hard when I turn it on and it kind of lets out a short buzzing "whine" when I turn it off. The game plays as normal. The issue only shows up on the DMD. And the loud sounds when turned on and off.

Beyond my very limited troubleshooting capabilities at this point. I've had a couple technical friends chip in, but they're stumped too. A grounding issues was suggested, but don't know where to go with it.

Any help, advice, ideas would be greatly appreciated.

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#2 6 years ago

Have a read through this. It may have a solution


#3 6 years ago

Thank you, I did try the applicable recommendations and everything seemed to check out.

I skipped the tests on the DMD controller, MPU, and power driver. The DMD controller and power driver work fine in JD and a friend tested the MPU in his DH and it worked okay.

The vast majority of recommendations revolve around those three boards, but they're not the issue

#4 6 years ago

Added a video to show the problem and you can hear the buzzing of the DMD.

The knocker even seems to jump slightly when the machine is turned on.

Measured the voltages going into the DMD and they check out.

#5 6 years ago

My first thought is bad/slow ram on the dmd controller. Does anyone else have expirence with xpin controllers?

#6 6 years ago

I have a new rottendog dmd controller and it produces the same problem.

#7 6 years ago

I just re watched the video. all the problems are in the same column. They are also NOT stuck pixels from a previous frame that are hanging they are phantom pixels. You can tell because the underline on E in "REPORT" Just shows up.

DMD Theory is that the DMD controller sends over a Frame and the dmd displays it. Being that they are all in the same column its most likely a Display RAM or Bad Display.

You can test the display ram in test menu.

Also given that the display is humming I think you might want to replace the display. Does the display from JD work in DH with no problems?

Anyone else have thoughts on this?

#8 6 years ago

The DMD works perfectly with no errors in JD.

The same applies to the MPU, power driver, and DMD controller. They all work perfectly in JD. (A pleasant unplanned benefit of owning two WPC-S pins.)

It has to be one of the other boards or something else altogether?

#9 6 years ago

AC ripple in one of the DC voltages? Also, try JD's ribbon cables in DH.

#10 6 years ago
Quoted from metallik:

AC ripple in one of the DC voltages? Also, try JD's ribbon cables in DH.

Thanks! I did swap the ribbon cables, but the problem still persists.

Someone suggested that I put the JD DMD into DH. I did put the DH DMD into JD, but the DMD worked perfectly in JD.

I don't know much about testing for AC ripples... any pinball related links to learn more? I googled around but didn't find anything helpful.

I have tested all the voltages that I could on the power driver and DMD, but they all checked out.

#11 6 years ago

A bad thing I notice on the video is many solenoid firing at the start. It's not just the knocker, but many flashers, and DMD start without its reset/blanking pin up. It's something on the CPU board (the CPU start resetted, top led is on at start). Also, a Flasher seems always on (near the ramp, upper left). I ask other people, is this normal?

#12 6 years ago

That aligns with my concern...

The machine "thumps" pretty loud at the start and it seems get a power surge every time the machine is turned on.

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