(Topic ID: 78518)

DMD problems

By marsgnu

10 years ago


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#1 10 years ago

Dear pinsiders, i have had my TS for almost a year now. But there has always been one problem: Two of the rows have always been out on my DMD. A few nights ago i fixed this by linking together some broken copper connections on the DMD using carbon glue. It worked great! But when i woke up the next morning the DMD wasn't lighting up at all. I can play just fine and everyting works exept the screen. I've checked the fuses and they seem to be fine.
Any ideas on what this could be? Thanks.

#2 10 years ago

Check and make sure your getting the right voltage to your dmd.

#3 10 years ago

Ok. I'll have to run to the store and get new batteries for my multimeter. But what could have caused this to happen?
It's so wierd.

#4 10 years ago

I'm not saying its for sure but you have to start somewhere.

2 weeks later
#5 10 years ago

I checked the voltage on the DMD controll board and i don't have any power on the 8th pin (the brown cathode).
I replaced the fuses but still nothing. Anybody have an idea what could have gone wrong?

#6 10 years ago

Yes. Your Dot controller high voltage section has probably failed, which is common.
They are usually a bit toasty to rebuild, buts it's never really beyond repair.
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Testing_DMD_Controller_Power

Ed at www.greatplainselectronics.com sells a nice kit to fix the board. Not sure about sources in Sweden.

--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#7 10 years ago

Thanks Chris! I took out the board and it looks a bit toasted on the transistor responsible for the 62v. I will take a closer look at it and return with my findings.

#8 10 years ago

I found that one of the diodes (D3 the red one) does not stop current from going both ways. Either it's broken or the board is designed to function that way. I can't tell by just looking at the schematics. Does anybody know?
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#9 10 years ago

Performing the diode test on the Zener at D3 should yield open one way, and about .7 or so the other way. It may take a second or two for the reading to settle out as there are caps in circuit.

You may get by replacing only D3, but it's generally recommended to replace everything in that side of the circuit, including Q2, Q3, Q10, R3, R4, R11, R12 and also R6 and R13 too, for good measure. Those 47K resistors fail most often in the circuit.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#10 10 years ago

Thanks man. I will try to get some parts tomorrow.
You guys are always so helpful

#11 10 years ago

Hi again. All the sites with a wpc kit shipping to me seem to be out of stock
Does anybody have a list of the parts needed to rebuild the 62v section? Maybe I can get them from a local supplier.
Thanks

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