Sega Naomi Cab monitor issue

[gratzme]

Hi, I have a sega naomi universal cab, with a sanwa 29E31S 31k monitor in it. The problem i have is that the picture is too wide for the screen. The picture is about an inch too wide each side. The monitor has a seperate control PCB which has some adjustments on it. However adjusting the horizontal pot does nothing except pinch the picture so the vertical lines bow inwards. I do have a schematic for the monitor but not sure where to start looking to fix the problem.

Any help would be great, thanks

[grantspain]

i reckon look at q411,413,414 c423

[gratzme]

Thanks for the quick reply, i have a multimeter but am a newb to monitors. Is there a guide on checking these components and what determins a faulty component? Also im from the UK, where can i get hold of new parts?