On Sun, 18 Jun 2000, Tony Duell wrote:
> HP were fond of suggesting that you do this :-(, even on machines where
> the PSU could easily fail in a way that the 5V output went up to a very
> high level (like 30V!) I often wondered if it was to sell more CPU boards
> ;-).
Zog! Why can't they build power supplies with a dummy load built in, or at
least a dummy load and a "test" switch so that the dummy load isn't attached
to the output when the computer is?
> > Just to be on the safe side, I'll try it out of the computer first if
> > it will work with no load just to make sure that there aren't any bad
>
> Be warned that a lot of HP PSUs of the early 1970's vintage (at least)
> don't like being run with no load. I normally load them with a 6V 5W or
> 6V 21W bulb (depending on the rating of the PSU) before turning them on.
I'll try to find a bulb to use. Is it only the 5V supply that has to be
loaded? I've got a resistor that was used for loading a Sun shoebox with
a tape drive and no PSU; I wonder if that would work. I'll have to see
what value it is; about a 10W resistor, IIRC.
Of course, if the PSU has no lose bits in it, and has already been
turned on by someone else before I got it, hasn't any damage that's
going to be done already been done? Hopefully I'll not get LARTed for
asking this, but, how likely am I to do any additional damage at this
point by turning it on attached to the sytem and checking the
voltages?
> Some service manuals warn (in bold printing) against running the PSU
> board with no load (it may even imply that the only load you can use is
> the CPU board!). I have never tried to run a PSU like that unloaded, so I
> have no idea what would happen, but I can't think it would be a good idea.
Thanks for the warning!
> really going on and work out my own set of tests. Mainly because I then
> understand what I am measuring and can make valid deductions if (for
> example) I see a very odd voltage or waveform at a particular point.
Makes sense; after all, that's what schematics are for, or, don't
people know how to read them these days? Alas, I don't have a set of
schematics, and will have to settle for whatever info. I can get from
someone who has any troubleshooting information - within reason, of
course.
> For much the same reason I've never found signature analysis to be a
> particularly useful technique.
What's signature analysis?
--
R. D. Davis
rdd_at_perqlogic.com
http://www.perqlogic.com/rdd
410-744-4900
Received on Sun Jun 18 2000 - 14:34:26 BST