maple classic™ 
so yesterday i got a 7915 power regulator (negative 15 volts, 1 amp) as a last resort attempt to rectify the PVM's power supply. after discussing the problem at length with the guy in charge of an electronics shop (he was very kind and patient to dissect the supply's schematic with me) we couldn't come to a good conclusion as to what's happening with it. so in the end i'm gonna try regulating the -15v (which is outputting anywhere between -17v to -22v) and seeing if that fixes it.
if the image stays good on the monitor, that confirms the problem was the -15v line on the PSU. if not, it might mean it's something else entirely in the monitor.
if the PSU is indeed at fault, i should probably find a more reliable solution than adding a regulator to the faulty PSU, but i'm not sure what that would entail.