Diagnose this Missile Command problem

[RayB]

OK So my brother in law sold a working Missile Command cabaret to someone, and the buyer had it one for a few hours only to have the game end up flashing a white screen.

BIL helps out by buying a tested working board off me and after checking the voltages, installs it. Bit later, that board ends up the same. We tested the board in my own machine and its flashing white, meaning it got damaged.

Test mode makes a continuous "raspy" noise which according to the manual is VBLANK failure. THe screen is flashing solid white or red during this.

Any ideas as to the cause and what parts to look at? I don't have an ocsilloscope.

I suggested that perhaps the Big Blue needs replacing.

[Level42]

My bet:

+5V drifting off on the AR2 because of bad edge connector. Check R.....what was it again, anyway, check resistors near the connectors for burns.


Anyway the story is like this: Atari included a self-regulating +5V circuit on the AR-2. Great idea. But after 25+ years the contacts between the PCB and the edge connector becomes poor. This results in the resistance increasing. Because of this, the AR-2 "senses" that the voltage drops so it increases it a bit. This process runs off when things get worse.

Incidentally (or not ?) my MC cabaret had the loosest edge connector I've ever seen on any cab. I replaced it.
Here's a video that shows it:


Some people mod the AR-2 so the 5V regulation gets disabled. I'm strongly against it because it's fighting the SYMPTOMS instead of the CAUSE.

[RayB]

I would never bother replacing a connector like that, but your video convinces me otherwise.

 

[Kevin Mullins]

Check R.....what was it again

Like R29, R30 or something.

Of course troubleshooting the now damaged pcbs may be a whole nother story.

[SirPeale]

R29 and / or R30.  It may be burned.  Good telltale sign.

[Level42]

I would never bother replacing a connector like that, but your video convinces me otherwise.

 

Believe it or not, I could SEE the difference on the monitor ! The colors were just that bit brighter after replacing the connector. Proof of the difference !

Glad I convinced you