300 W computer power supply

There are two kinds of PC power supplies. The original or "AT" supplies which turn on and off by a switch and the newer ones called "ATX" which turn on and off by the computer.

If the power plugs for the motherboard are seperate, you have an AT supply, if they are one 20 or 24 pin plug, you have an ATX. Some have both.

In order to turn on an ATX power supply, you need to short two leads on the plug. This is well documented, STFW for "testing ATX power supply".

I have not done this with ATX supplies, but I have used AT supplies as

5 and 12 volt power supplies. Most of them require a load on the 5 volt side, when I used one to power a 12 volt radio, I put an automobile tail light bulb across the 5 volt leads. It drew enough current to keep the supply active.

Note that while the DC voltage is quite clean, it is a switching power supply and many of them have lots of RF noise on the DC leads. I had no trouble using it for a VHF rig in a mixed HF/VHF environment, but many people have complained about using them on HF rigs.

Geoff.

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Look up ATX pinout and you should find the info you need to fire it up. Connect the power on wire to the standby wire and that should do it.

On most you'll need to load the primary output before the secondary outputs will regulate. On old AT PSUs it was the 5V, but on yours it's probably the

3.3V output. A power resistor or automotive lightbulb will work.

" snipped-for-privacy@yahoo.com" hath wroth:

It's amazing what you can find with Google:

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Thanks a lot for finding this for me! I really appreciate it. Lenny.

On Sat, 27 Oct 2007 19:50:21 GMT, "James Sweet" put finger to keyboard and composed:

No, connect PS_ON* to any ground wire.

See

IME most PC PSUs regulate by sensing a weighted average of the +5V and

+12V rails.

I believe this example is typical:

- Franc Zabkar

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On Sat, 27 Oct 2007 14:52:10 -0700, " snipped-for-privacy@yahoo.com" put finger to keyboard and composed:

You can convert your AT or ATX PSU to a tightly regulated 13.8V supply by changing the +12V sense resistor and removing the +5V sense resistor. You may also need to modify the overvoltage sense zeners, or whatever circuit is used to monitor this condition.

- Franc Zabkar

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