Help needed with Old PC PSU conversion

[Reflex1]

I offered to convert a PC PSU for use with a Li-Po charger
for a friend, if he supplied the PSU .

I have converted a few ATX units before,so no problem was expected :rolleyes:

However, the unit he has supplied I think is an AT model
with PS1 and PS2 connectors.

Has anyone converted one of these or have the pinout info?

[Malc C]

The July issue of Everyday Practical Electronics has a feature on how to convert a AT type PSU into a 13.5v 17A bench supply.

http://www.epemag.wimborne.co.uk/

Not sure if it's of any use to you, but might be worth popping into WH Smiths to see if a copy is still available

[Trevor_G]

Conversion of AT supplies is easier than the ATX. I don't worry about pinouts just hack the connectors off. Red is +5V,Black is OV and Yellow is +12V connect directly to wires of the correct colour.

Of course you may need to put dummy loads across the +12 and +5 to make the regulation work correctly. But this is the same as with the ATX suplies.

[Reflex1]

Thanks guys

It may be faulty,It's not starting up or turning the fan with mains applied.
Not tried a dummy load yet.
I'm guessing there is no "Power On" wire for AT supplies
Please correct me if I'm wrong.

(No helpful info label on this PSU case )

[Trevor_G]

It could be faulty but it is more likely you need the dummy load. What happens with some supplies is that with some supplies they come up so fast they create an overvoltage spike and trip the overvoltage crowbar.

The load is not critical but try to take at least 1A from the 5V and 0.5A from the 12V.

There is no PS_ON on an AT supply which is why they are easier to use.

[MatC]

I've used an old AT supply like this. I just plugged an old hard drive into the normal power outputs. This fooled the PSU into working, plus the project made a nice "spinning up" sound.

[Reflex1]

I got it working :)

Checked the PS1 connector and found a 5V supply present
from this I deduced it was in Standby Mode.

I removed the case cover and luckily the PCB was marked with the cable functions.

Connecting the White (PS_ON ) cable to ground
The Fan kicked over then shut off.

Using a H.D. as a temp dummy load, I turned it On again.
It now stays on and is working fine :)

The 12V line is a little low so I'll need to fit a suitable load to the 5V line.

If anyone else sees an ASTEC AA20290 PSU now you know how to sort it.
Thanks for the help all :cool: