Model 1 sega cd has sound but no video

Hey I have a model 1 sega cd that powers on flashes the bios screen for a second and goes to a black screen. It plays the music as well. I have replaced all the capacitors and it still has the same symptoms. The only different result I got was when I left the cd drive unplugged for trouble shooting. The system powered on and it froze on the bios screen with no music. I have tried 3 different genesis and cleaned all of the contacts. I have also tried different power supplies. I'm hoping it's not the Cpu or something. Has anyone else had this issue?

 

Hmm... Possibly a parcially corrupt BIOS? Did you check that everything was plugged in?

 

Just to make something clear in your trouble description.
Do you have any evidences that the game runs or it freezes on a black screen.

 

Seems like once it turns off, it shows for a split second then the screen goes black. That's my theory.

 

Hate to revive a dead thread, but I'm having this exact same issue. I just got a Model 1 in yesterday, I hooked it all up and when I turned on the Genesis, the screen flashed and then went black, but the BIOS screen music still played. This seems to be an issue that very few people have written about. Aside from my post at Atariage (which no one ever replied to), this is literally the ONLY other post I've seen about it.

Did you ever find out and/or fix the issue?

 

Have you tried cleaning the contacts for the Genesis<->CD connection?

 

Yes I did. I also found a clump of hair in the spindle of the CD drive and removed it. I put it all back together and now the CD doesn't power on at all. The power LEDs flashed and then nothing. There's still continuity in the fuse on both the Power Board and the Motherboard. The ribbon cable appeared to have a little tear, but I don't think it goes all the way to the wire as there's still continuity in all the contacts on the cable.

 

The video disappearing could be due to traces being cut to the RAM chips on the CD board. Check the board for corrosion.

The video is stored on the CD board RAM and transfered to the video processor on the Mega Drive through DMA. If the RAM empties for whatever reason, the CD CPU will crash but the process still running on the main CPU (in the Mega Drive) would still transfer the now emptied RAM to the video chip, making the image disappear.

It's a matter of checking what is going on with the CD CPU board.