Running an ATX PSU with no mainboard long term? (damages psu?)

  • Thread starter Thread starter wolfestone
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wolfestone

I've read about how you can short pin 14 & 15 on an atx psu to test it,
but I've also read somewhere that doing this repeatedly can damage the
PSU, since the atx spec. calls for a TTL circuit to pull pin 14 low.

Is there any other way without using a motherboard that I can get my
ATX psu to run, without fear of damaging it?

Thanks for any help!
 
wolfestone said:
I've read about how you can short pin 14 & 15 on an atx psu to test it,
but I've also read somewhere that doing this repeatedly can damage the
PSU, since the atx spec. calls for a TTL circuit to pull pin 14 low.

Don't worry about it. TTL level essentially means 0-5 volts, with low
being 0-.8V and high being 3.3 - 5.0V. Grounding the green wire to a
black will give you a TTL low. If you're really paranoid about causing
excessive current flow because of undershoot or overshoot (you
shouldn't be), connect the pins together through a 200-300 ohm
resistor.

If any damage will occur, it won't be from shorting pins 14 & 15
together but from operating the power supply without any loads, but
that's also highly unlikely. You can provide loads with power
resistors, each connected between ground (black wires) and the output
voltage (+5V red, +12V yellow, +3.3V orange). Some supplies don't
regulate well with less than 0.5-2A loads (or even run). Remember:

amps = volts/ohms
watts = volts x amps

Each resistor should be rated for at least 2-3 times the calculated
watts through it or it can easily exceed 100 Celcius.
 
Thanks very much for the info, it'll have a load on it, at least on the 12v
rails anyway.

Your advice is much appreciated!
 
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