MINIMUM load on a power supply.

_PD_ · 17 Apr 2006 at 15:27

Hi all,

I want to run a power supply seperate from my system, by attaching the two wires on the motherboard header.
However, apparently I need to have a certain amount on the power supply. I've been told that with only a couple of cathodes on there, it will turn itself off.
What is the minumum load required for a power supply to stay on, then?
If it helps, it's an X-connect 400W.

BONES__69 · 17 Apr 2006 at 16:38

Well some do and some don't and from personal experience most PSU's don't actually need a load to stay on. Just pull the PS_ON# low on the ATX connector (ie connect Green --> Ground (Any black cable)

P.S) Using a separate 400W PSU to power a couple of cathodes is ridiculous tbh!

Joe42 · 17 Apr 2006 at 16:42

I've been looking into using old pc psu's as bench powersupplies for various projects, and they all turn on ok but apparently some do need a load in order to regulate the voltage rails properly, so you might find that some of the voltages are a bit off without a load or with a very small load.

semi-pro waster · 17 Apr 2006 at 16:50

You could also stick a couple of fans onto the PSU to give it something more worthwhile to do but as BONES__69 says it is a bit over the top using a separate PSU to power a couple of cold cathodes

_PD_ · 17 Apr 2006 at 17:48

Yeah, it isn't powering them in a PC though. It's for on a desk, as an external jobby - but need some cathodes for lighting.
Cheers for the advice - at least I know I can try it without it going bang!

Stupido · 21 Apr 2006 at 02:50

you can run these via a dc adaptor i.e an adaptor powered by a wall socket plug .A lot safer and much more quiet than a psu .probably cheaper to run also .

I cannt provide a link unfortunately as i not sure if its against the rules .

fornowagain · 21 Apr 2006 at 04:33

BONES__69 said:
Well some do and some don't and from personal experience most PSU's don't actually need a load to stay on.

If you run a transformer secondary without a load the winding voltages can increase and kill components. Always put a small resistive load like a bulb on the load side. Electronics 101.