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DMD problem, help please!

cooldan

cooldan

i like pizza
10 Years
Joined
Jul 21, 2011
Messages
7,099
Location
Ealing, London
Hi all



check this out -it's the DMD from my DE Rocky & Bullwinkle:







it was working perfectly before i took the thing apart to clean behind it. i've taken the Sarge's advice and first checked all the ribbon connectors twice, then i tested the DMD in another game (it worked perfectly) and have checked the fuses in the power board (all good) ..... which leaves me noneplussed.



when i first turn the game on, the DMD is blank, then this occurs, which makes me wonder if something needs to warm up...... but the fact it occurred after being taken apart makes me wonder if everything was put back together properly or not. i did a little walkthrough. so maybe someone can see something out of place?









i suspect that Sarge is probably right that the connections are the problem, but how to test them further? any tips on testing components? advice?



thanks fellas :eek:
 
Looks like bad power supply. Measure the voltages on a dc scale, and again on AC.
 
Thanks Andy ill try to work out how to do that, and report back
smile-1.png
 
DCV-

Pin 1 -118V (from what i've been reading, this seems ok?)

Pin 2 -106V (from what i've been reading, this seems ok?)

Pin 3 key 0

Pin 4 ground 0

Pin 5 ground 0

Pin 6 15mV (from what i've been reading, this should be 5V?)

Pin 7 12V (from what i've been reading, this seems ok?)

Pin 8 32V (from what i've been reading, this should be 68V?)





ACV (i have no idea how to interpret these, as i though all DMD power was DC?)

Pins 1 to 5 read zero

Pin 6 10.2V

Pin 7 26V

Pin 8 68.1V



I also measured at the CN2 where there was 5.0V (from what i've been reading, this seems ok?)



Thanks mate
 
The very low 68v would explain the symptoms. Power supply needs repair
 
oh dear, that sounds like bad news for me but thanks Andy for the diagnosis.



while shopping the game, i dropped the playfield into the cabinet a couple of times, so i was wondering if i'd damaged any of the stuff in the base or sides there, and i suppose i'll have to learn the hard way. sigh. anything further i can do to narrow down the diagnosis, or do i need to try to get you round to fix it? what's the worst case scenario, costwise?



dang!
 
extract the power supply board and post it to me for repair. should cost no more than £40 or so
 
Thanks matey, I probably will after messing about seeing if I can understand it all for myself first, then deciding it's beyond my capabilities.



I've been measuring voltages on diodes D5 and D7. Am I on the right track?



[attachment=1427:ImageUploadedByTapatalk1349304326.513104.jpg]
 
D9 is the 68v diode. If you measure directly across here you souls be seeing around 68v. It may be fixed by replacing this one diode, or there may be other contributing factors.
 
Have you swapped power boards between games. This one is for a small dmd game, and is wired differently, so won't work in a large dmd game unless the original wiring in the pin has been 'adjusted'.
 
Er......

It's the one that came with the game when I bought it a year ago. Worked fine before I interfered. And I think R&B is a standard DMD rather than small or big, isn't it?
 
Big = standard. Not super. The board kind of works in the wrong configuration but has burnt up a bit, and chucks out two right voltages but not the correct 68v. So vaguely works but is not right for the big(not small ) display.
 
Let me have another look and get my head round the differences in the schematics to see what is going on.
 
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