Yes. In standby. In all modes between 1 and

Yes. In standby.
In all modes between 1 and 2 PIN optocoupler MAX. Forward voltage VF IF = 20mA - 1.4 V
For exampe use rom.by/files/SUNNY_ATX-230.zip


IC4 - standby power - In all modes between PIN 1 and 2 - ~ 1.2v .
IC2 - operate power. In standby mode between ground (black wire) and PIN 1 or 2 = 0v
IC3 - ON/OFF operate mode. In standby mode between ground (black wire) and PIN 1 or 2 = 5v