Testing VT101 Power Supply

tony duell ard at p850ug1.demon.co.uk
Sat Jan 17 10:53:30 CST 2015

> In my case of vt100 powersupply test (i hope that i remember corretly) i need to load 5V with a small load.
> With nothing connected, some voltages fail.

>From what I remember, the VT100 and VT101 PSUs are very different. The former is a fairly conventional
SMPSU, albeit one which (as was typical for DEC at the time) has the control circuitry on the output side of 
the isolation barrier and a little linear startup PSU. The VT101 has a large mains transformer and a regulator
board, I think some of those regulators are switchers, but they run from a lowish input voltage (not mains) and
the isolation is provided by the big transformer.

I don't know about running them with no load, although I could well believe the VT101 PSU will work
correctly like that.


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