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DMD Not Working

R

RetroRepair

Registered
Joined
Aug 20, 2012
Messages
125
Location
Essex, Uk
Well I finally got my project, a pretty manky looking Getaway cabinet.

For a start the CPU board wouldn't fire up. I got 2 blinks on the status LED which said the RAM was dead, so I replaced that and the board fired up.

Things seem to work ok but the DMD won't come on. I wiggled some of the wires around and the display came up very briefly albeit with what looked like some garbage around the text so I figured I'd replace the DMD board RAM too. I am not sure if moving the wires is actually what caused it to spring to life though, later it came on with lots of random dots which slowly disappeared over time, with less and less dots each power on.

The voltages seem good at the connector according to the pinwiki guide and it looks like the data output is ok though A12 on the controller board RAM is constantly stuck low.

Does anyone have experience with this sort of issue? Or is anyone local to Leigh on Sea, Essex that can test my DMD or display controller board?
 
RetroRepair said:
I wiggled some of the wires around and the display came up very briefly albeit with what looked like some garbage around the text so I figured I'd replace the DMD board RAM too. I am not sure if moving the wires is actually what caused it to spring to life though, later it came on with lots of random dots which slowly disappeared over time, with less and less dots each power on.
Click to expand...

Sounds like you need to reflow the connector pins of the wires you were wiggling around.

Good luck!
 
I will give it a go but no amount of wiggling does anything now. I think it was a coincidence and it just sprang to life for a short while. It's not done anything at all in several power ons now.
 
Ok tried that and no dice, still dead. Didn't look much like there were any dry joints anyway.

Does anyone know if the logic ICs on this board NEED to be HC components as apposed to LS? I have a ton of 74 LS logic here but hardly any HC.
 
RetroRepair said:
Ok tried that and no dice, still dead. Didn't look much like there were any dry joints anyway.
Click to expand...

The reflow is to repair hairline cracks rather than dry joints. You did do both ends of the cables that you were wiggling around? have you tried wriggling them again?

RetroRepair said:
Does anyone know if the logic ICs on this board NEED to be HC components as apposed to LS? I have a ton of 74 LS logic here but hardly any HC.
Click to expand...

Before you replace chips I'd say you need to find out why the RAM is constantly stuck low...!
 
I did the CPU board, fliptronics board and DMD board.

Yeah I'll get to the source of the dead address line but wanted to know if I was going to need to order parts. Bootleg JAMMA games are a great source of parts and I have loads, but rarely do they carry the HC type (external pullups vs internal) which can behave differently depending on the circuit.
 
So it looks like the data coming from the CPU going directly to the controller board is crap. Just a noisey, weak high signal. I tried swapping the LS244 ICs just before the EXT connector but it didn't help. Does this mean my 6809 is bad? Is the data supposed to look like this or a nice solid strobe?

It's weird because when the data leaves the 6809 it looks ok, though could do with being pulled up as touching it does change the signal. When it comes out of the LS244s though it isn't strobing anymore.
 
You've gone way over my head with pulling things high and suchlike. Have you tried turning the ribbon cable to the display the other way up? That can cause these display problems. Also ensuring that you haven't put the sound and display boards in the wrong places (don't ask how I know!).
Anyway, back to your ls's and hc's!!
 
Do you mean making sure pin 1 is where it should be? Yeah tried that. Also just ruled out the 6809 as I swapped it with the sound board CPU.

The game plays fine (with the exception of a few switches) just can't see the damned video which means I can't do a proper diagnostic test. Makes the video mode pretty hard too :confused:

Bit stuck now to be honest.
 
Definitely not the ribbon cables, just reversed them all both ends.

Guess I'm still down to DMD, DMD Controller or CPU. Less inclined to believe it's the CPU given my trouble shooting steps.
 
Ok, so I checked my voltages again and seems I lost -112v and -110v! Oddly enough I still have 63v.

So anyway, I looked at the board and found Q5 and Q4 read as dead short to ground on the center pin. Q4 actually had all three pins shorted to ground. Out of circuit, sure enough dead short on all three pins on Q4, Q5 was ok. So I replaced them and they shorted again right away.

I'm starting to think that BR2 or BR1 are dead. I've ordered the parts to rebuild the HV section anyway so I guess then we will see what we have.
 
Ok so I blitzed the HV section as I suspected I had blown BR1 or 2 and now I get this:

i58.tinypic.com_2h7gqw1.jpg

This is just garbage, there's no semblance of the correct image in there at all. It does change randomly, but not when I move through menus or start a game etc so it seems to me it's getting no data :confused:

Here's a video too (in the video I'm doing nothing other than power up the cab):

View My Video

Any ideas from here? I have changed out the RAM several times (I socketed it) to no avail.
 
Ah, that's a typical example of a ribbon cable being on incorrectly... check you have pin 1 to pin 1 at both ends and that you're not one row of pins over...

If that's all ok then try an new ribbon cable.
 
I don't think it's the cable as continuity tested ok at the CPU and dmd board. All cables are seated properly.

Unplugging the data cable to the dmd changes nothing btw.

I'm going to have to get the probe back out and see what's going on I guess.
 
RetroRepair said:
Ok so I blitzed the HV section as I suspected I had blown BR1 or 2 and now I get this:

i58.tinypic.com_2h7gqw1.jpg

This is just garbage, there's no semblance of the correct image in there at all. It does change randomly, but not when I move through menus or start a game etc so it seems to me it's getting no data :confused:

Here's a video too (in the video I'm doing nothing other than power up the cab):

View My Video

Any ideas from here? I have changed out the RAM several times (I socketed it) to no avail.
Click to expand...


That's also what a Babcock display will look like if the 12v is missing
 
Well my bet is it's knacked.
Have you not got another you can try in the machine ?
Check that the voltage is correct before doing so.
 
Good call. First (and only) thing I know about a knackered DMD is this:

take it out and try it in another machine - if it works, it's fine so your problem wasn't the DMD.

Alternatively try another working machine's working DMD in the game showing a problem, if it stops working that also confirms the problem is not the dodgy DMD itself but something else in the circuit.
 
Hmm that's a lot to worry about there. I don't have another machine to test and no one I know locally has a pin :(

Still not checked what the output data is doing, will try and do that today.
 
Well here's a nice list, pig in a poke anyone?:

I probably didn't mention before but if you missed the image and video above, it's a HS2.

1. I checked the data coming from the controller board and it looks like it's doing something so I'd have expected the dmd to react somehow untill..

2. Noticed the DMD was getting a bit pink after being on for a bit (still displaying garbage). I checked the voltages coming from the dmd controller. -700VDC??!! This was my supposed -112v. It fluctuated between -500 and -700. As did most of the other voltages, wildly. I know my DMM is fine. I'm glad I didn't borrow any parts to test now.

3. Certain switches have now decided to activate from boot. After a few minutes they stop acting up (I have just completely disconnected the DMD board by now).

4. Earlier, the sound started going mad. Random tracks were playing and sometimes no music at all. This is the first time this has happened in about 20 sessions. Took about 20 mins for it to calm down.

5. The beacon on the backbox is just going all the time now. Before today it was intermittent. Always worked when it was supposed to though. I first got the cab, it worked only when it was meant to.

So I now don't trust ANY board in this thing. DMD issues could be down to power driver, controller and/or CPU board. I also won't replace anything individually as I'll be here from now till doomsday (murdering parts/board along the way) so I will just save up and replace every board to my utter dismay.

Moral of this sad tale? DON'T EVER store your pin in your shed. EVER. This one had spent 5 years in a shed and it shows in both the state of the machine and the electronics.
 
There is no way the DMD controller board can generate 700vdc, that must be a miss-reading

Are you getting stable voltages if you measure the AC taps on the secondary of the transformer?

With all the ribbons disconnected and just the CPU running on it's own, do you get clean data?
 
The data from the CPU to the DMD always sounded muddy, but then I have heared that from the probe before on other systems and the data was fine. Not enough experience I guess with WPC systems. This was tested with the cables disconnected. I did replace the buffers and main CPU but data sounded the same.

I did think the -700vcd was unlikely but on a retest, same deal. It did fluctuate but after 30 secs or so I got correct voltages on the others, but never changed on the -112 output. Could have been a poor connection to the earth braid but wouldn't explain the orange glow of the DMD turning pinkish after a bit.
 
RetroRepair said:
The data from the CPU to the DMD always sounded muddy, but then I have heared that from the probe before on other systems and the data was fine. Not enough experience I guess with WPC systems. This was tested with the cables disconnected. I did replace the buffers and main CPU but data sounded the same.

I did think the -700vcd was unlikely but on a retest, same deal. It did fluctuate but after 30 secs or so I got correct voltages on the others, but never changed on the -112 output. Could have been a poor connection to the earth braid but wouldn't explain the orange glow of the DMD turning pinkish after a bit.
Click to expand...
Power Driver boards are normally pretty bullet proof And fairly straightforward To repair, I would try testing the boards in someone fairly locals game. Or send them off to someone I can't imagine all the boards are at fault it's more likely a transformer issue or ribbon cables.
 
I'm far from an expert here but it sounds like issues with multiple boards (which would be odd). The only thing connecting all the issues is power. I'd go back to basics and check the voltages from the transformer and work forward from there. Check the voltages to the dmd board are within spec as they pass through the power driver board first. If one of them is out then there's a good chance the dmd voltages will be wrong. If they're right, check your work on the hv section. It's easy to get it wrong (don't ask how I know!).

Finally, have you reseated the ASIC on the CPU board? That can cause all sorts of issues!
 
it sounds like wherever you are taking your Ground from is suspect with high readings like that...

Best to check your In Voltages on J605..... Once you know these are good, then it's deffo nothing before the board.... Start easy and get more complex... ;)
 
Well I thought first thing's first, let's check the fuses on the DMD board.. 8 and 4amp?? These are supposed to be 375ma :rolleyes:

So I decided to go through the rest and there's a bunch that were far too high so I'll be putting messing about with this on hold until I get the new fuses in. I'll probably grab a known good DMD controller before then though so I at least know if that's where my issue lies or not when I get the fuses. I'm not spending any more time messing about with that.

Thanks for the advice guys!
 
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