these monitors are known that they solder out their "line transformer" (hope it is the correct word )
Yep... Line transformer, high-voltage transformer, flyback, whatever you want to call it... Bad solder joint, most likely.
And, of course, it goes without saying... Be careful. Even after leaving the thing unplugged for a day or two, and following discharge procedure, it can still have some voltage trapped in it..... (Not that I've ever blown up a monitor while working on it.... no.... not me.... [whistles innocently] )