19 Dec
2015
19 Dec
'15
10:31 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Robert
Jarratt
Sent: 19 December 2015 17:20
To: 'General Discussion: On-Topic and Off-Topic Posts'
<cctalk at classiccmp.org>
Subject: RE: VAX 4000-500 PSU Overload?
test
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Mouse
Sent: 19 December 2015 16:09
To: cctalk at classiccmp.org
Subject: Re: VAX 4000-500 PSU Overload?
good
But getting something in series to measure load
is going to be
really awkward, [...]
As in, you don't have any such thing to put in series, or you don't
see a way to get it in series? I've got a couple
of 0R1 resistors which
work
nicely for
that in conjunction with a voltmeter that can
handle millivolt
measurements;
you might be able to get something similar. Mine
are 10W, and, while
they are designed for bolting to a heatsink, they can probably handle
at least
2 or 3
watts, which means some 5-6 amps, in free air.
(Though that then
drops about half a volt, which can be a problem when you can't put it
on the
input
side of the
regulation.)
I think the suggestion was to put an ammeter between the PSU and the
backplane. That would be awkward to make all the connections with the PSU
out of the machine. Also difficult is to make a dummy load for a bench that draws enough current to test that it can sustain
its rated output at
full
load (or some decent proportion of full load at any
rate).
Regards
Rob
Rob,
Seeing as it already seems to have over current sensing, I guess it has some
small resistors in there so perhaps it is possible to measure the current. I
notices one looks like this:-
http://uk.farnell.com/welwyn/oar1-r020fi/resistor-1-0r020/dp/1200359
Dave