Genesis/SMS with av mod has bouncing/scrolling screen

[beigemore]

I've done composite video mods for my Genesis and my SMS, but when the screens go black and come back with something on the screen, the screen always bounces once. During normal gameplay the video is fine, it's just kind of annoying to see this in places such as in-between levels, or during cut scenes.

So, for example, it would happen where like the Sega logo comes up (both systems), then screen goes black, then when the title screen comes up, the video scrolls up very fast exactly one screen and then the video stays... then I start the game, screen goes black, then when the first level comes up the screen bounces/scrolls again, and is fine until the next black screen.

Any ideas as to what could be causing this? This is also now occurring when I use the built in AV out ports on both systems, which is wear I'm pulling the video and ground signals from. It's not a major issue, it's just kind of annoying.

[indianknightrider]

Have you got a NTSC system? I have 1 ntsc ps1 and it scrolls the screen on bright scenes like logo's and cutscenes, you need to check if the grounding is done properly, I have done this composite video mod to my MDII successfully http://www.youtube.com/watch?v=u_32EiHhr34, I have ground wires set up to each single Rca piece, just like the man said.

If you don't have the cables securely taped, there might be some interference, I also tape mine and checked Pal mode to have perfect picture.

[ooXxXoo]

Make sure you have a good "Ground" source to the connectors.....

...

[beigemore]

Everything is properly grounded. I just tested both systems on a CRT TV and they don't have that problem.. it only occurs with my plasma. Oh well. Looks better on the CRT anyway.

[beigemore]

Just in case anyone else comes across this, I found the cause behind my problem. I was using an av switch that supports composite and s-video. Apparently the switch automatically converts any composite video signals it receives to s-video, and something was funky with the converted signal it was outputting. I pulled the switch and plugged my system directly to the plasma tv and it worked fine, which is also why it worked fine when I used it on a regular tv without the switch...