Help with a Power Supply

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Apr 2 17:04:00 2004

> Since I am not Tony Duell, I will just be tossing the old

Since when do I have a monopoly on test equipment ;-)

> power supply. However, before that, I would like to
> know if there is a simple way to test the old power
> supply to determine if that was the actual problem?
>
> Please don't mention anything that requires me to open
> up the old power supply. I only have an old analog
> volt meter and could put a few light bulbs into a test
> circuit, but that is about the limit! It really is not that


Well, that's what you need for the first test. Put bulbs as a
load on at least the main outputs of the PSU (that's the +5V, and maybe
the +12V lines at least). Try to take at least half the rated current
from each rail (so if you have a 5V 10A supply, you want, say, a 6V 30W
bulb, or enough smaller bulbs in parallel to make up the current). Then
measure the output voltages with your meter.

If it passes that test, then you really need to look at the outputs with
a 'scope to look for excessive ripple.

> important, but it sure would be interesting to know if
> that was the specific problem.

It's _always_ worth making sure you've fixed the real problem. Randomly
replacing parts with no proof they had anything to do with the problem is
no way to fix anything. Alas making measurements before changing things
has gone out of fashion ;-(

-tony
Received on Fri Apr 02 2004 - 17:04:00 BST