9 Jun
2020
9 Jun
'20
4:04 p.m.
On Tue, 9 Jun 2020, Bill Gunshannon via cctalk wrote:
For the unlabeled white wire this must be -9V return, such as say with
the H7109-AA PSU used with the VAXstation 4000 VLC, the H7819-AA used with
VAXstation 4000 60/90/etc. and storage expansions or the H7821-00 PSU used
with several systems, where the -9V supply circuit is isolated and used, I
believe, for serial line drivers/receivers. It might be worth checking.
Maciej
For the
VXT-2000 with an H7109-B the rated voltage and current values
are printed right on the power supply label:
+5.1V, 7.81A
+12.1V, 0.62A
-12.1V, 0.46A
-9V, 0.2A
Fixed width character pinout diagram:
+=================+
-9V | Yellow | Orange | +12.1V
+--------+--------+
??? | White | Black | Gnd
+--------+--------+
+5.1V | Red | Blue | -12.1V
+--------+--------+
+5.1V | Red | Black | Gnd
+--------+--------+
Gnd | Black | Black | Gnd
+=================+
The mystery is the White wire. The power supply label only lists 4
output voltages. The White wire appears to be routed to the Ethernet
daughter board. The measured voltage appears that it might be floating
slightly negative, somewhere around -1.5V when the Ethernet daughter
board is installed and around -5V when it is removed. Maybe it is a
high impedance earth ground connection? It appears to be connected to
the shield of the Ethernet BNC, which measures around 1M-Ohm to the
chassis ground when the power supply is disconnected from the main
board, and around 0.75M-Ohm when the power supply is connected.
Thank you for that. Mine has no labels or anything. It is PC Board
with Digital, Side 1, Side 2 and a number I don't recognize on it.
I guess the -9V is the only odd one but you could easily get that
from a -12V line. I may get to fix it yet.