How to get a PC/server PSU working?

[NeilP]

I have a selection (and more all the time) of various PSU's from servers. I want to load a few of them up and see what sort of current they put out and compare to spec.

When plugged in to the mains, without a mainboard connected, they do not power up...I believe this is because is there is a signal wire that needs shorting out/feeding with a switching voltage to fire the beasts up....any one tell me how this is done?

I could just play around but thought I would ask first

Cheers

Neil

 

[liveforphysics]

Pin's 6 and 8 hook to pin 10 (ground) and it turns on. (at least for the extremely popular HP power supply)

http://www.rc-monster.com/forum/showthread.php?t=27554

 

[AussieJester]

I can tell you for certain a 'standard' PC PSU you must connect the green wire on the atx plug to any any black wire on the plug to start the PSU->

View attachment Capture.JPG

Small loop of wire or a paperclip does the job if you don't want to cut the wires and twist them together or
get fancy and install an on off switch LoL

KiM

 

[amberwolf]

Note that some power supplies may not regulate properly if you start them up with out any load on them; even a small load of a few hundred mA would probably be enough; a separate one on each 12V line it has (some only have one, some two or three), one on the 5V, and one on the 3.3V. Sometimes only a load on 12V is needed and the rest stabilize from that. Sometimes no load is required.

 

[NeilP]

Ok, thanks

I'll probably solder a switch in and can find something to load up the pack with, cheers

Since there is a -12v line shown on the jpg, would it therefroe be possible to run an ATX supply as 24 volt? -12 to +12? or is the -12 v line not as good for current as the +12 v line.

Obviously need to be careful with regard to the chassis earth , so insulate the case, but otherwise...is it a possibility?

 

[x88x]

One to three things you'll have to do, depending on the age and design of the unit. For all but the oldest models, pull the 'power on' (green) line to ground. The other thing you'll have to do is put a constant load on the 5V (red) line and possibly the 3.3V (orange) line as well. Without those loads, you won't get full voltage or current on the supply rails. In mine, I use 10Ohm 10W power resistors for the load (warning, they get quite hot). Worklog here if you're interested.

 

[NeilP]

Ok, cheers

I'll start playing with this in the next few days

 

[x88x]

Whoops, that should have been the 5V and 3.3V, not 12 and 5. Original post is edited to be correct now.

 

[def215]

thanks x88x,

that tutorial was helpful. i just recently acquired a 12v computer psu to convert into a bench power supply for testing and i coulnt get it to fire up. all i need is to load my 5v output and it should power up. for my 3.3volt supply, should i just use the actual ground when i use it since there was no specified ground for it?

 

[x88x]

thanks x88x,

that tutorial was helpful. i just recently acquired a 12v computer psu to convert into a bench power supply for testing and i coulnt get it to fire up. all i need is to load my 5v output and it should power up. for my 3.3volt supply, should i just use the actual ground when i use it since there was no specified ground for it?

In a PC power supply, everything shares a common ground, so any ground wires will do just fine.

 

[regmeister]

deleted

 

[texaspyro]

A lot of CPU power supplies don't like being connected in series with another supply.

And you almost certainly cannot connect their individual outputs in series since they are not isolated from each other (they share a common ground). You can usually get intermediate voltages (like 7V from across the +5 and +12 outputs) as long as you are aware of the current and grounding issues.

 

[NeilP]

Well you can...supposedly...according to many posts...but you have to isolate the ground first, so each pack is floating...So then you must ensure the individual packs do not touch..and you do not touch them...so mounted up inside another case