Re: Testing PC (ATX) PSUs...

"Bubba" <nickname@xxxxxx> wrote in message
news:Xns97D29769D2E39bubbachipsetone@xxxxxxxxxxxxxx
Greetings to all,

I don't see the original post, so posting follow-up to this and
editing out instead.

I just can't seem to figure out what am I doing wrong. Are these, so
caller brand PSUs really so bad that they can't hold few amps of bulb or
there is something else at stake? I even tried to let the PSU heat up a
bit and connected bulbs afterwards but there was no improvement. I must
also add that 5V and 3.3V are connected to Socket A MBO with few PCI
cards, just to keep the balance (some PSU's won't start unless they have
some load on all rails).

If we ignore the properties of the light bulb and just on amps, a few
amps on 5V/3.3V drawn by the motherboard would be enough for modern
ATX 2.03 PSU to put out a decent +12V.

But as mentioned by Ralph here
Lamps are sometimes a poor load for electronic circuits as the resistance is
very low to start with and as they heat up the resistance goes up. In some
cases the cold resistance will be so low it will not let a power supply
start up or will cause it to go into an over current protection mode.

A fews years ago, friend and me attempted the exact same thing and was
similarly advised that bulbs are a BAD way to try this with.
Subsequently, we used resistors network to create cheap (relative to
an actual load tester) but still controllable load testing system.

Then we tried to use mosfets switches and such to create a more
demanding test environment but unfortunately never completed that
project as other real life things intruded.

Lastly keep in mind that the ATX spec allows +/-5% regulation so 11.4V
is still "acceptable". IIRC, the spec also allowed up to +/- 10% under
really high load conditions.

--
A Lost Angel, fallen from heaven
Lost in dreams, Lost in aspirations,
Lost to the world, Lost to myself
.

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