Vertically rolling image with S-video - not composite.

[existensmaximum]

My friend is having a problem with some video game consoles. He's got a 32" computer monitor for gaming, and it does not have a SCART-input (since it's not a TV) so he connects video games via composite, component or S-video depending on what's available. This is the monitor he's using:

http://www.hdtvsolutions.com/Samsung-SyncMaster_320P.htm

I've got a PC-Engine that I've modded for RGB, and I've tried it at my friend's place by tapping composite video from the SCART pins of my RGB cable - no problem, it plays fine on his monitor.

But recently, he bought himself a PC-Engine of his own, and I performed an S-Video mod using this schematic:

https://s16.postimg.cc/fqc3c5ct1/Turbografx_16_S_Video_Schematic.png

The only difference is that I used a 200Ohm resistor on the Luma out. This works great at my place, but with his monitor, we get a vertically rolling image. What can be the cause of this, and how can we solve it?

He's tried many different consoles on his monitor: N64 (50 Hz), Wii (50/60 Hz) and Gamecube (50 Hz) has been working fine with composite video, but recently we also tried to connect a Sony Playstation (50 Hz) (the first model, not PSOne). Everything looks fine in the startup menu, but once we get into a game - the image starts rolling vertically. I've tried the same Playstation with two different TV's at my place, no problem.

Any ideas what's causing this?

[Keith Courage]

Hmm that's an odd one. Did you maybe accidentally tap V-sync instead of the actual composite video pin? I did that once on accident and had a scrolling image when I was performing a component mod but only on some televisions.