I'm going to ask another question here - similar topic, hopefully someone will help me understand. The LED for this power supply stays on all the time, but I think its supposed to be related to the current limit function. Someone on a different thread had posted a link to the manual, which had a schematic for this power supply,
R19 is 2.2K, R20 is 10K. I've looked at pin6 of the opamp U3 - when the power supply goes into current limit mode - this pin is pulled to less than 0V (-20mV), but when it is not in current limit mode, this pin is high (around 35V). From what I understand, R19 and R20 would form a voltage divider for the Q3 base, and what I measure is 0V at the opamp pin 6, 35.6V at the Q3 base, and 36.4V at the +ve rail in current limit mode. When I'm in voltage mode, I measure 26V at pin 6, 35.8V at Q3 base, and 36.5 at the +ve rail.
I guess I don't understand what the LED and the Q3 transistor are supposed to be doing. If they wanted the LED to be on all the time, I would have thought that there would be an easier way to accomplish that.
What should I try next to diagnose what is going on?