WG U3100 - picture shifts/flickers vertical

[Carsten Carlos]

Just moved my cab one room further - the last time I played I notices my monitor (Wells Gardner U3100 -arcade vga monitor) has a little vertical flickering!  

Somehow the picture moves/flickers up and down, barely noticable, but still driving me nervous! It flickers only less then a pixel height up and down, but it's definitely there!

Anyone an idea where I could start to look at?   I've all circuits diagrams here -would be easier to find the fault when the picture would be dead instead of this!

I tried other plug-sockets in the house as well, also I turned of the marquee-lights, no changes there. In windows it's still a standard vga-monitor, switching from standard to optimum in the graphics-driver doesn't change anything. I made no changes in my configuration anyway.

[tom61]

Jiggle your V.Hold knob a bit.

[Carsten Carlos]

Good idea - would love to, but it seems that is has none!   At least it's not in their servicemanual/pdf-file I got here.

[tom61]

Odd. There should be a Vertical Hold knob.