monitor se-m21c 25 inch

[peterbe]

some time ago i bought an arcade cabinet to use for Mame, there was still a monitor in it but is  was broke. I found out there was a capacitor and a diode blow up and replaced that. I wanted to check if the monitor was any good and started paying around with advancemame for dos. But until now i wasn't been able to get a real usable image so now i am wondering if the monitor still has problems, i made a wrong cable or it is a advancemame problem. So maybe the first question is if someone has experience with the monitor i have, i have the follwing information about it:
on the board it says  segai se-m21xx , on the schematic i have se-m21c 25 inch and 28 inch (mine is a 25 inch). I found some information on the net about a se-m21xx but it are only 13 and 19 inch.

[grantspain]

how do you mean usable image,scrambled?

[peterbe]

i experimented with the advcfg utility and tried allot of the video modes cga ega vga
and only in ega i got something that looked like the test image of this utility
what i got is an image that is flickering and that is the testimage like 3 or 4 times and overlapping a bit so instead of the one triangle you have top and below i got 3 and not next to each other but overlapping a bit

[grantspain]

your monitor is getting the wrong frequency from the pc

[peterbe]

yes but what frequency would be wrong the ega? 25 khz if i try cga or vga the picture is even more bad

[grantspain]

have you tried your horizontal hold pot?
if you get more than one picture on the same screen the freq is wrong full stop
i guess this is mame,i am not up on mame(fake arcade)stuff but i have seen things about powerstrip in this forum helping with frequency problems
maybe its worth looking at those threads first
i can't find that monitor anywhere how do you know its set on 25khz

[grantspain]

yes i can its a happ controls monitor that is 15khz freq,try setting the output at cga and adjust the horizontal hold pot

[peterbe]

experimented with the horizontal hold and cga 15 khz got a much better image but i couldn't get it totally steady so i tried extended 16 khz and then the horizontal hold and got a stable picture looks good and tried several resolutions only missing some red colour i think have to look into that
anyway much tanks have been a big help