Depends on the original CRT monitor signal format, and horizontal/vert sweep rate, If standard analogue VGA and up it should be no problem, The lower sweep rate monitors or older EGA TTL types will pose a problem.
Also, if built in CRT monitor on OEM dedicated systems the signal pin out as well as the standard has to be known or 'scoped to document it.
Al.
I just noticed its Fadal Forum, but the above will still apply.