/vr/ - Retro Games

So i've been getting together bits for RGB on all my consoles for awhile now. The other day I bought a thing called a 'Joytech model JS965 AV Control Centre' which basically is a powered RGB hub where I can plug my PVM into the output socket and all my console's RGB cables into one of 4 inputs. My PVM (a 2042QM) looks fine with just a RGB cable from a console (i'm testing my Superfam and MD1) to an RGB - RCA breakout adapter with cables going to the monitor, no problems. When I add the Joytech hub in between however the picture is wobbly at the top 2-3 inches of the screen. I thought it was the joytech box at first but I just used the same system with a 9 inch PVM and it worked fine. Any ideas people?