Genesis 1 video encoder

[gumbyandpals]

On every model 1 Sega Genesis I've seen, there are these bands of interference. This picture is what it looks like without a game in. It's usually not this noticeable. This only happens through composite and RF outputs (both come from the same pin on the encoder ultimately).

Does anyone know if this is an artifact created by the encoder chip (CXA1145)? If that's the case I would try to replace it with its clone the MB3514 which was used in the CDX and doesn't have these bands.

I'm hoping someone has some ideas.

http://img518.imageshack.us/my.php?i...sc01662bj1.jpg

[omnedon]

Are you using the original and correctly rated AC adapter? The Genesis is very tolerant of improper AC, but you will get some nasty video banding like you describe.

[gumbyandpals]

Yes, I am using the original AC adapter. I don't have it to look at right now but it's the 9v 1.2amp or something like that, not the 10v for the Sega CD.

[extrarice]

I have that same problem with a Model 2, but it goes away when I have the 32x attached, regardless of if I'm playing a 32x game or standard Genesis game. I'm pretty sure I'm using the proper AC brick, but I'll check.

[gumbyandpals]

Yes, it does go away with the 32x because the 32x takes the RGB signal from the genesis and has its own video encoder to create the composite signal. That's what make me think this is an encoder problem.

The RGB signal straight from the genesis is free of this banding btw.

[omnedon]

I've never seen this, except with mis-rated AC adapters.

?

[gumbyandpals]

If you want to look for it, play a game with a solid background color. The example below is sonic 1. If you look you should see that the "solid" blue background is not so solid. It has bands. It's easier to notice when playing the game because the picture moves through the bands.

Like I said earlier, it's strange because this only happens through the RF or composite video output.

[extrarice]

I've never seen this, except with mis-rated AC adapters.

?

I'm using the proper SEGA-brand AC bricks. For what it's worth, the banding is terrible on my model 2, and is barely noticable on my model 1. Both using composite.