Vanguard pcb problems

[Belike]

I have a strange problem with my Vanguard pcb, when I switch the cab on, everything works great until the first game you play is over.
After the "Game Over" sign the screen collapses and I can see only vibrating lines.
If I switch it off and on again, I can play 1 game again, but after it acts the same way.
Any ideas what could be the problem?
Otherwise if somebody have a working spare Vanguard pcb, I'm up for it!

[level42]

Uh first check if it's a monitor or a PCB problem ?

Otherwise, the first game that's REALLY Game Over 

[Belike]

LoL!
If I leave it in demo mode it doesn't collapse.
Could it be a monitor problem in this case?

[level42]

Wonder how it looks like. Can you post a video (youtube).

If it happens exactly at the same time every time it could also be a ROM problem.

[Belike]

Wonder how it looks like. Can you post a video (youtube).

If it happens exactly at the same time every time it could also be a ROM problem.

Voila:
http://www.youtube.com/watch?v=OMJ90cCiMZI
It's starting to be interesting from 1min.16 sec.

[level42]

Looks like a PCB problem to me. Looks like bad ROM code making it crash. Is there a test menu to check the ROMs ?
If not try to re-seat the (EP)ROMs carefully.

[Laschek]

That's not a monitor problem, the game itself crashes. Like André suggested it might be a ROM Error. Did you try first aid: removing, cleaning, and reseating all socketed Chips, esp. the Roms. Also check and reseat all ribbon cables (if any), and check the voltages. Increasing +5V slightly might help.

[Belike]

I reseated everything in the pcb, and I have another nonworking board, so I could swap all the chips one by one, but it was worse than the original situation.I think if the +5 V wouldn't be correct, the pcb wouldn't start and play only 1 game.
There is no test menu and as I'm an electric noob, I don't know which roms are the "game" roms.
Maybe an eprom burner and a working pcb could help in this situation.

[Laschek]

The game roms are supposed to look like this if it's an original board (which I assume):



Sound Roms should be marked "VGS".

Ok, increasing +5V is something like a shot in the dark, quick'n dirty means of first aid, but I've seen many boards behave in all kinds of strange ways when +5V was too low (or too high, for that matter). I'd give it a try, can't hurt (at least if you don't increase to 10V ). Remember that for some boards +5.0 is too low.

[Laschek]

double post - please ignore

[level42]

and be sure to measure on the board and not on the power supply !

[Belike]

Thanks guys, I will try what you advised!

[Belike]

I swapped only these game roms again, but nothing changed, the game running until 1st game over:

When I swap this big one next to the game roms, there is just a white screen:

There is also a big one on the lower pcb, if I swap that, it also doesn't work:

There are also 2 golden mostek chips, if I swap one of them, the game running partially in white:

I couldn't try to set the 5V yet, I think the game roms are ok, I have a feeling, that one of the big ones or the mosteks is defective.

[level42]

The 6502 is the processor (the big one).

[Belike]

The 6502 is the processor (the big one).

Is it possible, that the processor causes this problem?