The Aiwa Mega-CD CSD-GM1 is doing something rather interesting with its video output. Unfortunately, interesting isn’t necessarily a good thing! I’ve been getting these strange wavy lines across the picture while running it from my external power supply. Actually, they’re more like dotted lines, and they’re quite noticeable when you look closely at the screen.

It’s not just the camera playing tricks on us, either. The interference is visible on the CRT itself, although I’ve also got to allow for the rolling bands that appear when filming a television. I only like grains in my wheat, thank you very much. I certainly don’t need them all over the picture!

The curious thing is that the interference seems to disappear when I run the same hardware from what I believe is an original transformer. The picture looks considerably cleaner, which is encouraging, except that the original power supplies have been giving me trouble of their own. That’s the reason I’ve been experimenting with this external supply in the first place.

For comparison, I’ve also shown composite video from a Mega-CD II. That picture looks beautifully clear, apart from those rolling bands caused by the camera. Then I switch back to the Aiwa using the external supply and the wavy interference returns. It’s a fairly convincing demonstration that the way I’m powering this machine makes a difference to the picture.

I’m particularly interested in this result because even the damaged Aiwa mainboard can produce a clean picture when connected to the original-style transformer. That makes me suspicious of the external supply arrangement, although I haven’t worked out whether the issue is insufficient voltage, electrical noise or something else.

So if anyone has any ideas, I’m all ears! The Aiwa is at least running well enough for me to worry about video quality now, which is a considerable improvement over having a completely dead machine sitting on the workbench.