26 Jun
2023
26 Jun
'23
2:28 p.m.
Hi!
As I'm preparing to setup my old hardware, I fetched two VAXstations
(4000/90 and /96) from storage and cleaned one of them throughoutly.
Then I gave power (to both of them), but both won't really start:
all 8 diag LEDs are on (--> power available but CPU didn't start
executing instructions.)
I took the PSU (from the cleaned /90), a DEC H7819-AA, and measured
it. Unfortunately I didn't find pinouts or schematics at a first
search. The plate states that there should be 3.3V, 5V, 12V, -12V and
-9V. I found most of that:
+------------------------------------------------------------------+
| o |
| DEC H7819-AA PSU 10 +---+ 1 |
| (view at the bottom side) | | |
| | | |
| | | |
| 18 +---+ 9 |
| o |
| +-------+ +-------+ |
| | Fan | | Fan | |
+----------------+-------+----+-------+----------------------------+
With above pin numbering, this is what I could find / measure / deduce:
3V3 brown 10 1 blue 12V
3V3 brown 11 2 black GND
GND black 12 3 red 5V
GND black 13 4 red 5V
GND black 14 5 black GND
5V red 15 6 black GND
5V red 16 7 white -12V
5V red 17 8 blue (0.78V)
(4.91V) lilac 18 9 brown (-1.65V)
Most values look plausible, except those three in parentheses. At
least one of them should probably be -9V wrt. GND I guess, but that's
totally absent. And what's the other two? (If I got the colors wrong:
Please forgive, I'm red-green blind.) That could be some "power-okay"
indicator, or external switch-off?
Maybe anybody has faced these issues and can point me to some docs
or "well known to be failing" capacitors? I'd be quite grateful for
any hints! :) ...and hope that maybe the above drawing/measurements
will be helpful for anybody else later on.
Thanks,
Jan-Benedict
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