Magnetek PSU

[Billie]

Hello to All,

I'm new here and also fairly green when it concerns electronics.
I've been playing around with arduino's and other small stuff, but want to grow and learn more

I've got a couple of Magnetek HPR4915 PSU which came from a couple of old Tally printers from work and since these got multiple DC outputs I thought I could use it as a base for a adjustable bench power supply.
One of the outputs is interesting since it has 40V 3.3A. So this should be more then enough to create a adjustable bench psu. But when I connect it to the mains and start measuring the output wires the maximum voltage I get is 20something Volts...
Could it be that I need to attach some load to get the full 40V?












Regards,

Billie

[ocset]

Maybe you have to put fan on, or make it think the fan is on to make it work properly.
Or does it have an enable pin.
Or a standby pin?

[Cliff Matthews]

See if you can find a service manual for whatever MT model it came from. It won't likely give you schematics but it will give you enough voltages and block diagrams to go on. I have 2 load tested PSU's from Lexmark 24xx forms printers and they also produce 40v (a 2.5a). I got mine to work by putting a resistor on a power save pin. One day I'll pull these from storage and use LM723's and 2n3055's for a split supply.

As has already been said, it may require a load like a fan to work (some clues may be in the trouble-shooting section).
Also, keep in mind switching power supplies sometimes have >300v DC on the bulk input caps... depending on what novice skills you have, I might recommend shelving the unit and buy something like this for now: https://www.banggood.com/GOPHERT-CPS-3205-0-32V-0-5A-Portable-Adjustable-DC-Power-Supply-110V220V-p-934530.html

[Cliff Matthews]

Is this the unit? (looks totally enclosed..) Have you identified voltages with respect to the black wires?