HP-1000E PSU

From: Frank McConnell <fmc_at_reanimators.org>
Date: Sun Jun 25 14:50:36 2000

"R. D. Davis" <rdd_at_smart.net> wrote:
> Well, I've made the initial tests... seems that the problem may be
> before the regulators and after the fuse. Since I didn't have a 21W,

Based on the following:

> Hooking up the VOM, I got a reading of about 3.5mV for the 5V supply
> and between that and zero for everything else. So, it's not completely
> dead, but, close to it. And, yes, the fan is spinning.

...I think you may be right. The flowchart goes on to ask: "Is >= 0.6
Volts measured from A3A6TP1 to A3A1TP1? WARNING!! Use VM with
Floating GND". If the answer to this question is no, you're supposed
to replace the preregulator board (A3A1) or the control board (A3A5).
Else, the next question is whether fuse A3A6F1 is blown or missing,
in which case you're supposed to replace the fuse, else replace
transistor A3A6Q1.

Then you go back and look for +5V CPU on the crossover board again.

How to decode some of those numbers:

Leading A3 is the power supply.

A1 is the preregulator control board, which is a vertical board
plugged into the power supply motherboard just behind the terminal
block near the front of the 1000E.

A5 is the control board; it's the vertical board all the way at the
back of the power supply.

A6 is the power supply mother board. A6F1 looks like it should
be a fuse a little bit behind A1, and A6Q1 looks like it should
be the largish transistor closest to that fuse.

> > adjustment is the +5V ADJ potentiometer that is visible on the power
>
> Does adjusting that make a difference with any of the other voltages?

I don't know. The next couple of tests that the flowchart takes you
through are simply "is <some power supply voltage>" in tolerance at
the crossover board?", and if the answer is "no" then you get to
replace a transistor on the power supply motherboard, or in one case
the power supply motherboard.

> What's the difference between M and I/O in the supply v. column?

I think M is the supply that goes to the memory bus, and I/O is
the supply that goes to the I/O bus.

> Something tells me to leave this pot alone at this point.

Yep.

> As I don't have a set of schematics, can anyone tell me what to check next?
> Meanwhile, I guess I'll go poking around and see what voltages I can find
> in various spots.

As Tony points out, there is stuff in there that can knock you on your
hindquarters or worse, and I'm guessing that's why you're supposed to
use a voltmeter with a floating ground in one of those tests above.
Be careful.

That said, sorry to take so long writing back, just haven't had time
or space between my ears to sit here with the manuals and try to
figure things out from them. The curse of gainful employment strikes
again.

-Frank McConnell
Received on Sun Jun 25 2000 - 14:50:36 BST