Strange 'cut-off' across top of monitor screen.

[ckong]

OK, I'm running Groovymame with an Ati radeon 4550 HD card and CRT Emudrivers on a Windows XP PC, spitting out 15 Khz through a homemade VGA > RGB Scart cable (including 5V + 100 Ohm resistor and 12V from the PC power supply).

I'm testing this setup with 3 European 21" RGB Scart TV's (2x Philips and 1x Sony) and 1 true 15K 27" Barco DCD2740 monitor, and I'm having a particular issue with the Sony TV and the Barco monitor. Where the 2 Philips TV's present a good overall picture and geometry, the Sony TV and the Barco monitor show a 'cut-off' section across the top of the screen, see the picture of the the Barco displaying a test screen in 640x480 resolution.

What causes this and how can I solve it?

[Dochartaigh]

I suck at MAME settings, but generally speaking you need to change your front porch in the timing settings to adjust the image. OR go into the service menu and move the image down and/or a little less tall (or if the TV is older you might have to open it up and adjust the pots inside to do these adjustments).

Every TV has the image centered and adjusted a little different. Every source also gives a slightly different picture. On old CRT's there just isn't one perfect setting which works for everything 100%.