Hello everyone, I'd been trying to fix this model for 2 days .. no short circuit anywhere, replaced NX20P5090 (because they tend to short out) but still 5v not converting to 20v, so I decided to study the PD controller U4201 (RTS5455) circuitry and stumbled upon the VMON line with R4208 resistor open and replacing restored the 20v. I hope it helps someone.