Dying VaxStation 4000 VLC - help?

From: Mark Tapley <mtapley_at_swri.edu>
Date: Wed Nov 13 14:59:01 2002

John Allain wrote:

>Get the PSU part number and I'll look it up,
>or check:
> http://pages.prodigy.net/ppsjm/PART+ACU-20NUMBER.htm

Prodigy says that URL is not found. However

http://pages.prodigy.net/ppsjm/PART%20NUMBER.htm

works....Oh. I get it.

AAARRRGGHHHH! ;-) But no H7109 listed.

And Antonio supplied:

> The PSU is an H7109-00.

Google for H7109-00 turns up nothing.
Google for H7109 turns up two dealers (the cheapest in Irving, TX(!), at
http://www.jtcomputer.com) which list an H7109-C as a "VAXSTATION 4000 VLC
POWER SUPP". This is the same thing, yes? Anybody have experience with, or
opinions on, that dealer?
There are also multiple other H7109 (-A, -B) listed, which look not to be
what I'm after.

---
Tony Duell wrote:
>Most DEC machines have at least one power-OK line from the PSU.
I want to figure out which that one is.
>OK, how many pins is the connector between the PSU and the mainboard?
Will count, but order of 9.
>You've identified +5 and +12 (and ground) -- presumably on the disk power
>connector.
Exactly. It was an informed guess - Orange insulation for +12, and red for
+5, and Black for Ground.
>Can you find those on the mainboard connector?
There were similar colors on wires from the mainboard PS connector to the
Power supply. I actually measured the voltages on the Power-supply side of
that connection, not on the mainboard or the disk-drive connector. I
checked that the resistances between what I thought were the corresponding
pins on the mainboard PS connector and the mainboard disk-drive connector
were 0 (with everything unplugged), just to be sure. Probably I should
double-check voltages on the disk-drive connector, to rule out connector
problems at the mainboard-PS connector.
>What's left?
>Probably at least one -ve voltage. And maybe a power-OK line.
Oh, I also found -12V (found by accident - needle swung the wrong way) and
it was about -11.5 V (I think). That was a blue wire. Forgot to report
that. There were about 5 wires I did not check. I'll look at them tonight;
if I'm lucky, the power-OK indicator, if present, will switch from one
state to the other while I'm watching it. Hopefully it'll stay in each
state long enough that I can see the needle move.
>One of the few components that gets better when warm is a faulty
>electrolytic capacitor.
I have not figured out correlation between temperature and working status.
Yesterday morning it worked for a long time when booted up from cold, then
failed. Cycling power did not make it work better.
>It's a pity you don't have a 'scope (to look for
>ripple on the PSU lines) or an ESR meter (to check all the electrolytics
>on the secondary side of the PSU).
I've been thinking that, but unlike my wife's hobby (sewing) my hobby does
not turn a profit (or rather, displace household expenditures). Though I
might claim some credit if I ever get around to fixing that $%^&*
Stylewriter....
Anyway the o-scope and ESR meter budget is zero at the moment. Sigh.
>This does sound like power trouble. If not, then maybe gently warming
>(hair dryer) and cooling (freezer spray) the components on the mainboard
>will identify any that have gone thermally intermitant.
Ooo, neat idea. The hair dryer I have. Don't have freezer spray, but maybe
I can use a bike tire or something. Is there any reason (other than the
possibility of slowly fatal electrocution) not to try the same trick on the
power supply? I'd have to run it opened up and avoid touching the
heat-sinks, etc, but I don't recall any reason it shouldn't run that way.
								- Mark

Received on Wed Nov 13 2002 - 14:59:01 GMT