I have 2 HP ESP120 Power supplys and one of them I use on my 2m amplifier in the upstairs shack.
This only because I do not have 3 phase outlet in that shack for a Delta SM70-45 power supply which I use for the 70cm EME amplifier.
Have made some study of how others are enabling the ESP120 and I am a bit puzzled how they do.
The most used way seems to be published by N4GA where he advice to short out 3 pins without any description of their functionality.
I read the only datasheet I could find on a similar power supply that looked like a drop in replacement for the HP supply.
This shows that when connecting these three pins together you short out Power on, PSKILL and the present pins.
PSON is the remote control input connector.
PSKILL is a emergency kill pin that switch the PS off if it looses connection to the 5V rtn.
Present pin is an indicator for the system to show that a PS is inserted in that slot.
Connecting these pins do not seems correct and I am actually surprised it works but it does.
Only reason I can se is that if the Present pin have an internal path to ground.
In my mind I would connect the PSKILL to the 5V rtn constantly and switch the PSON to 5V rtn to enabel the PS output and I tested to do so and it worked perfectly.
The reason for all this was that I wanted to remotely control the PS from the amplifier and when connecting the Power on switch of the amplifier between the PSON to 5V rtn it works great.
I have occasionally seen some noise from the PS on 2m. but I placed capacitors on the output connections to PS outer cover and also placed a copper braid screen around the two 10 mm Square cables to the amplifier and grounded that in the outer housing as well.
This seems to fix the worst noise but its important to ensure the cables are routed in a specific way to totally get rid of any noise.
This is most likely caused by the fact the 2m antenna is placed only 4 meters above the shack where the PS is located.
Got a half promise that a friend with an excavator will come this or next week to fill the whole for the concrete base and to dig down the anchor points for a 22m mast I have laying to use for tropo and a HF beam.