Gensis Mk1 Problems

Hi Guys, i'm new here. I found this site when I was searching for help fixing my dead Megadrive/Genesis Mk1. It's a 1990 VA4, which just stopped working one day several years ago.

I've dug it out, recapped all the electro's, and cleaned the cart slot, but the problem is the same. I'm running into an LCD tv using an RGB cable that works perfectly on my spare Megardive and MasterSystem mk1's.

When it has a cartridge plugged in, the music works, but the picture just displays vertical blue and white stripes with the typical blue borders. It doesn't boot the MegaCD either (also a mk1).

Does this sound like a typical failure mode of something I can fix?

The console has great sentimental value so i'd like to fix it if possible.

 

You get a display, but it's only the border color that works?
Sounds like either a trace near the VDP is bad, a VDP pin has no connection, or the VDP is dead.

 

I get a display, mine is the PAL 50Hz model, so it has borders. The outside border, surrounding the area where the game is displayed is light blue. The actual game screen area is a series of vertical white and blue lines.

I guess that if I have sound from the AV port, the video encoder is working ok.

The image is the same using composite, so it's either the VDP or the VRAM?

 

Yep, sounds like it. Of course it could always be an obscure CPU or bus error, but I'd start with the VDP and its connections.

 

So if it's the VDP it's a 72pin chip, and that's not really fixable

 

If it's the IC itself, you can only replace it. This isn't easy, as you probably know
Oftentimes it's just a trace though, so you need to do more debugging to close in on the problem.

 

Sounds like vram gone.