12 May
2001
12 May
'01
1:31 p.m.
Would a "modern" switching supply ie: a cheap, generic PC supply
have enough output to run a vintage machine? I had considered doing that
with some totally fried HP supplies I've got hanging around. For the HP
1000 series machines ... huge modular aluminium boxes with plenty of
room inside to hide a modern supply. As I recall [from a frequently
faulty memory] the HP drew about 20 amps or so on the +5 line. Shouldn't
be too hard to pull a couple of the faulty cards to make room for the
much smaller [physically] supply. Might be a problem with lack of decent
air circulation for cooling though.
Again from memory ... even the CE's really didn't want to fool with
repairing the PS units on these. When I bought a bunch of HP gear there
were 8 or 10 dead supplies that had been stashed away to maybe fix
"someday'.
Craig
Tony Duell wrote:
Forgive me if this is a silly question; it never got covered in my digital
electronics classes :-).
Is a modern switching power supply a suitable replacement for an ancient
(and dead) linear power supply in a classic computer (PDP-11, FWIW)?
Electrically, it should work. Most modern SMPSUs do have a minimum load
current (if you don't give them enough load they may not work, and may
even be damaged), but any classic computer should be enough load for any
reasonable PSU.
However, I personally perfer to keep my computers as original as
possible, and in particular I don't like replacing well-documented,
repairable sections (like PDP11 PSUs, for which full schematics are
available) with an undocumented modern part (and to be honest, the DEC
PSUs are a lot better made than, say, 'generic' PC PSUs).
I've never seen a PDP11 with a linear PSU (and I've worked on many
models). Many of them did have a mains-frequency transformer, but it was
followed by _switching_ regulators, at least for the main outputs (+5V,
-15V).
What is the machine, and what is the PSU? It's likely somebody here has
the schematics for it.
-tony