Differential Diagnosis Dreamcast

[Blaine]

Okay people...

Female Dreamcast of French descent. Approximately 9 years old. Complains of garbled video:

Hi everybody !

I'm new here, and I hope I won't ask for something you already answered...
I buyed a VGA Box here (thanks RacketBoy, I received it in 4 days in France, I was really impressed !), so I happily tried it and it appears that all I can get are "funny colors" (see screenshot). I assume it doesn't come from the VGA box (since I tried SVHS output too, assuming it doesn't go through the little chip, and same result). My original black SCART cable wasn't working anymore and I used to use a white RGB cable (which I've lost, so I can't test again). The last time I tried (some years ago), my Dreamcast was working properly.
Has one of you encountered the same problem ? Is the Dreamcast RGB output faulty ?

It's not Lupus.

Seriously though, I saw this post on another forum and it's WAY over my head. Any ideas at all?

[l_oliveira]

Few things I can think of:

Video DAC is damaged.
VRAM is faulty
PowerVR chip is faulty
PCB is faulty and at least one of the connections from PowerVR to VRAM or Video DAC is broken.

I had a motherboard with similar problems here. I tried to swap the ram chips and it didn't fix the problem. Then finally I gave up from repairing it and removed it's Video DAC which repaired another Dreamcast with no video but with sound symptoms.

[Tiido Priimägi]

Funny colors = H sync is not at correct level, none of my LCDs like DCs H sync when its not buffered, all of them will display same funny colors !!! My old CRT monitor works fine though....

[l_oliveira]

Blaine:
Did you try that Dreamcast on a CRT TV ?  (I have no LCDs here...)

Having a test run on a VGA monitor using a VGA box is a good idea too.