hng64 graphical glitches

I run my hng64 on a supergun via rgb cable and all games (ss64, sswr, buriki1) show graphical glitches - missing pixels / distorted picture (e.g.: character portraits, some special move effects, crows in ukiyos stage, buriki one logo, etc.).

what could be wrong - defect board or carts?

If it is doing it with all games, I would look at cleaning the contacts on the motherboard (and the carts while you are at it.)

i second that.