So I picked up a JP that needs some work. I would like to get the DMD fixed before I put too much effort into cleaning it up. Anyway, I power up the machine. The DMD comes on, IIRC it states the ROM version then goes blank. I decided to play a game to see if anything else was broken. At some point during the game I looked up and saw an image on the DMD. I was playing for quite a bit and even had multiball going but the score was way too low to be my current score that is when I noticed the DMD was froze.

I did install the v6.0 software as well as the req'd display ROMs but the problem persists.

Any tips? I re-seated cables already, I may try to replace cables but I'm not sure which ones I have and I don't intend on buying any new ones since I don't think that is the problem.

Yes

I'll take a look... I do have a bunch of spares.

If this turns into rebuilding the HV section... I'm in trouble. I failed miserably on my LAH HV rebuild, sold the game with no display but new owner went the Stern display route which I may do and get myself a colorDMD for Met

Good stuff here. I will report back after I work on the game this weekend.

Fuse clips and voltages check out fine. If I unplug the little 5v connector and reattach it I get the display ROM version screen and blank again. I played a few games and could not get anything past this screen.

I don't have any DE games to swap parts from

I replaced the ribbon cables and fuses (they seemed corroded).... Still the same problem... I see the ROM version at startup then nothing. If I pull the 5v and reconnect while powered up then I get the same result.

The higher voltages are withing a volt of the spec below. The lower voltages are within a couple tenths of a volt.

1: -110 VDC
2: -98 VDC
3: Key
4: GRND
5: GRND
6: +5 V
7: +12 VDC
8: +68 VDC

I tried a new ribbon cable from the MPU to the display without any luck. I'm not sure if this is a re-import but I can take a look at this tonight.

Yes, that is what I meant but I did replace both ribbon cables.

My bad... Testing at the 5v plug, I see 4.9V. I don't see any test points.

And I am tempted to send you the boards but I would really like to be able to do this stuff myself. I failed miserably on LAH when its display went blank.

I did a little bit of probing last night with a mini o'scope (Clay's recommended tool). Some signals looked good and others I was not sure about. I will poke around again tonight now that I have a bit more knowledge (may have to watch Clay's videos again).

On another note... Do you think my DMD is good? On someone else's recommendation, I replaced the DMD with what I thought was a good one but I got nothing. I then checked voltages and the 98v was missing, when I swapped DMDs back again the 98v was back. Interestingly enough, this was the DMD from my old LAH that I failed miserably on when fixing the HV side of the Power Supply. Maybe that was not the true issue?

I likely have a laptop power supply, nothing from a desktop though.

Another note about this game... there is a ton of corrosion all over it. Not battery acid damage but rust. Everything metal near the playfield is rusty. Seems like the only thing rusty in the backbox is the springs on the battery holder though.

OK... I probed U17 & U19 and got nothing from any of the pins. I assume this means my DMD controller is bad. What is the trick to fixing this?

OK... I'm a dumbass. I get some activity on the U17 & U19 chips. Seems pretty one sided though for both chips. I'm going to assume that is bad.

OK.. finally got some time to start looking at this again. I started poking around under the playfield as I know that have at least one issue under there and maybe it is contributing to the DMD blanking. Under the playfield, I fixed a couple issues. 1. Coil wire for ball launcher was cut and loosely spliced with tape, I soldered and heat shrunk the wire back to one piece. 2. one of the wires (jumper to the other switch) for the slingshot switch was off, I soldered that back on. 3. diode strip with nothing on it (see pic), I don't know what should be attached to this.

I lower the playfield and power the game on..... Now the DMD is completely... BLANK. I don't get the startup flash any more, I used to get the ROM version info.

I'm sure that I did not mess up (1) from above. (2) looks exactly like the other switch, but I pulled the same wire off to check... DMD completely blank. I likely moved some wires around under the playfield looking for issues but nothing too far that may have pulled a wire off. I inspect all wires again and don't see anything out of the ordinary. Side note, my T-Rex does not grab the ball when he dips down (I don't see anything obviously wrong with him but it is not fixed yet either).

Any new tips? My DMD is completely blank now

IMG_20161007_213904126 (resized).jpg

Ribbon cables have been replaced, wiggled, jiggled, and flipped and nothing seems to change. For the record... The game boots and plays but the only thing on the DMD is the initial boot up screen with the Display ROM info. Nearly everything seems to work during game play aside from the TRex does not scoop up the ball. I'm guessing there is a switch problem there but I think it would be easiest to troubleshoot once the DMD is functioning.

Toying around with this again last night.. a bit after the ROM version display I got a "command 80" message on the DMD.

Turns out it is NOT the DMD controller.

No idea... Still working on it but getting discouraged quickly.

New Rottendog board. Display ROM version comes up when game is powered on but then goes blank and usually stays blank. The game will play fine though. One time "Command 80" flashed on the screen and another time I got some display but it froze and the game played on. But 98% of the time it goes blank and stays blank. I'm using the latest ROMs, but the game did the same thing with the previous ROMs. I think it says V5 for the display ROMs.

Well... I got it down to the CPU board. Swapped boards and the game works.