On 6/9/2020 11:51 AM, Glen Slick via cctalk wrote:
On Tue, Jun 9, 2020 at 9:04 AM Bill Gunshannon via cctalk
<cctalk@classiccmp.org> wrote:
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.
As long as we are talking VXT-2000, I have this on file, figure it would
be useful for future googling of the list if
this were here as well. May be a repeat of info from an earlier post,
or maybe elsewhere.
I didn't save the source of the info, but looks like someone named Matt
Millman did it.
The setup is as follows: HP Envy laptop running MOP boot daemon,
connected to Lantronix LTX-C twisted pair
ethernet to AUI converter (not the same as a twisted pair MAU). This is
then connected to a cabletron coax
MAU with a 10BASE5 vampire tap. The coax runs over to another MAU, which
is connected via an AUI cable to
my VXT2000. I didn't think of it, but it would have been nice to have a
real DEC MAU on the VXT2000, I've
got several DEC h4000's I could have used.
https://www.youtube.com/watch?v=A5T2GlAN2N4
http://tech.mattmillman.com/projects/10base5/
