Newbie weird settings T.V. out NTSC

[MRHooked]

 

Hi.
Just finishing software setup for my first mame cabinet & wondering if someone could help. I have done a lot of research on this problem & can't find similar problems or solutions.

I am using a G400 in linux to drive 2nd port tv out NTSC to a TV. Using advance menu and advancemame.

I seem to only get results at settings   5-150 / 60 / 60 in advmame.rc

if I try the ntsc standard setting of 5-150 / 15.73 / 60 won't work.

Any ideas would be appreciated on fix or reason for such high hclock.

Thanks

MRHooked