DE SMALL DMD ISSUE "command overrun". SOLVED

[BallyWilliams suck]

Hi all.

Have an issue on a Hook. The small display keeps going blank, and comes up with "command overrun". Did the basic stuff, swapped the display, ribbon cables, updated all the roms ..... no change.

I read a thread which suggested a bad 6264 on the cpu. Swapped. Still same.

Next step is to swap the cpu, but rather than blindly carrying on swapping - doe anyone have any info on this issue ?

Many thanks.

 

[BallyWilliams suck]

 

[strobey]

Will be watching this thread with interest... Fascinating!

 

[Moonraker]

Which roms Jamie? Display roms or Game roms...?

 

[pinballmania]

Had this issue with a pinled replacement display. Unfortunately didn’t resolve the issue. Pinled suggested replacing the capacitor on the display but made no difference. Not very helpful.

 

[BallyWilliams suck]

Replaced both display and cpu roms.....

Which cap did they suggest andy? Although it's doubtful both the pinled display I tried and the original display both have the same fault.

Only thing left is a cpu issue surely?

I've read several threads with this issue. No one seems to be able to solve it

 

[pinballmania]

The one on the pinled power input. I don’t think they really had any idea/interest.

 

[Moonraker]

What's the area under the batteries like? Looking at the manual, under the batteries is blanking, CPU and clock. I'd suggest any corrosion in that area would probably give an error message like that...

 

[BallyWilliams suck]

Cpu is clean. I can swap it out, but would of liked to have heard from someone who's found a solution. I'm sure andy would have done all these things already - so I'm not hopeful.

 

[BallyWilliams suck]

Update. I've found several threads with this issue (as already stated). NONE have come to any sort of conclusion.

Swapping cpu boards has sorted the problem, so although I have no idea what is causing the issue on the pcb without further investigation - this should help any future folk with this fault .....

It only seems to be a problem on the small 128x16 dmd, so I'll wager the faulty pcb will run in a later game without this issue. Possibly......

 

[BallyWilliams suck]

Update - I checked all the resistor arrays and caps connected to cn22, which is the alphanumeric segment driver socket. All checked ok, apart from some bad readings on ra23. Removed and checked ok outside the pcb. Then noticed some of the caps c32-39 were shorted to ground. Lifted one end, and now reading ok. Going further back, they connect to outputs of pia 7b.

Removed and tested in my boardmaster 8000 and surely enough it's bad.

I don't think this pia being faulty in this way would affect the dmd system as it has its own driver pcb. So this fault, caused by a dodgy 6821 pia would probably only affect a small dmd DE game

Hope this helps everyone.