26" jamma display problem arcadevga

[mogse]

Hi

i've just got a 26" monitor jamma cab but can't seem to get a sharp display.
when i hook up my arcadevga mame PC, the display seems to be out of focus dispite adjusting the focus on the back of the monitor?the text have a fuzzy outline etc..
can anyone please tell me if this is the symtoms of a faulty monitor on the way out or is it just I have to adjust the settings in the software?

I'm used to a 19" jamma  and did question myself if it was just because of the size of thing (being bigger & closer to it you see more imperfections)

maybe its my jpac set to the wrong setting

i'm pretty new to mame and jamma cabs currently both jumpers are on 31k & 15k (default)

thanks for the advice