I have fixed a few of these same power supplies - they are used in several HP models. In all cases, the solution was to replace ALL the electrolytic capacitors since they are quite prone to leakage. Remove them all, scrub the board with alcohol, scrub it again, scrub it again, then replace the caps with new (non-Chinese) ones, say from Nichicon, Panasonic, etc. If you find electrolyte on the board, also check the trim pots as I had electrolyte get into some of them. Unfortunately, you will need to spend about $25 (US) to buy the couple of dozen new caps.
Even if the problem with your power supply remains and requires further diagnoses, it is still worth the effort to replace the caps because if they aren't leaking now, they soon will be.