17 Jun
2012
17 Jun
'12
5:02 p.m.
I am making progress testing the power supply for my 11/04 (BA11-K chassis)
and so far have worked through the power control box, transformer, fans and
the 15VDC regulator/Power Line monitor but have one question for the
group....
I am seeing in tolerance output voltages from the 15VDC regulator but I
haven't loaded tested it. Is this something I should do or if the unloaded
outputs are within tolerance then it is safe to use (once the other
regulators are done)?
If the votlage drops on load, the machine might not work correctly, but
in general no damage will be done.
It is rare, but possible [1] for the output of a regualtor to rise on
load. It's therefore always safest to do a load test [2] but it's less
importnat than chackign the PSU off-load in the first place.
[1] The normal casue of this is an swithcing regulator -- the H744, for
example, but not IIRC< the +15V supply in the BA11-K -- where hte output
capacitor has got a high ESR. You can get some spikes on the output
several times the correct outptu votlage,adn they get worse asnm the laod
increases. I had a suppy in an HP device that would work fine off load
but where the crowbar would trip as soon as you loaded it. A newer
capcitor solved the problem, once I'd worked out what was going on.
[2] Car bulbs are nominally 12V, but car electricak systems run at 13.8V
or so when the engine is running. Such blubs should stand 15V for a short
time -- long enough to test the supply.
-tony