Blown fuses or shorted diodes on the output of the standby transformer are frequent culprits. These can be identified using a multimeter in Diode Mode Fluctuating Output: Usually linked to "bad" or bulging main capacitors
Short the green wire (PS_ON) to any black wire (Ground). ps42419ha schematic work
: Includes the fuse, MOV (surge protection), and line filters. PFC (Power Factor Correction) : Active PFC circuitry to improve efficiency. Standby Circuit Blown fuses or shorted diodes on the output