This Porta monitor had what appears to be common fault. It would sometimes fail to boot, it would boot but the display would turn off while still glowing dimly after few seconds following bootup. Failure was caused by the SMPS LM2577ADJ. It would start passing 15V instead of 9.5V and the display would turn itself into protection mode. It appears voltage is gradually drifting away from the set 9.5V and eventually will lead to failure of the panel itself in certain cases but most of a time it can be caught in time and repaired before further damage is done.

It is the first sort of TO220 ish based chip with 5 legs screwed to the heatsink.

Thanks to somebody at GroupDIY for identifying the voltage issue which helped me find and eliminate the fault