Anyone good at fixing TVs?

I picked up this Philips colour CCTV video monitor for really cheap on eBay, and, as expected, it’s got a slight problem. The picture appears fuzzy in parts. Not grain, but it’s got a horizontal zig-zag distortion going across the screen. The distortion isn’t consistent throughout… there are some bands of clear picture, mainly towards the center of the screen. Adjusting the brightness/contrast makes the distortion change - making it brighter makes considerably more distortion, and it seems to be less distorted when darker (but far from perfect).

I’ve tried connecting it to a few different sources and it produces the same results.

The seller said “it’s something to do with the high-voltage power converter, but be careful fixing it”… helps a lot.

Help?

EDIT: It’s a Philips LTC2910 9" colour CCTV monitor (using it as a poor-man’s video editing reference monitor)
PDF information sheet here: http://www.lvw.com/LTC291090.pdf