10 Aug
2026
10 Aug
'26
9:27 a.m.
On Sun, Aug 2, 2026 at 8:44 PM Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
The ground was the problem. For some CRAZY reason,
pin 5 of
the 9-pin serial connector of the KA630-AA and cabinet kit
has a 1K Ohm resistance to system ground.
I don't doubt that you had a problem with ground, but on a MicroVAX
console port, Pin 5 is not ground. Ground is Pin 7.
There are pinout similarities with a PC DE9 serial port, but AFAIK
it's not intentional.
1: Protective Ground
2: Transmited Data
3: Received Data
4: Request To Send (RTS)
5: Data Terminal Ready (DTR)
6: Data Set Ready (DSR)
7: Signal Ground
8: Shorted to pin 9 on MicroVAX and VAXstation 2000...
9: ...series systems, otherwise left floating.
BCC08 cable has 8-9 shorted because it was the standard console cable
back when "real" serial ports were on DB25s. I forget which machines
actually use it to detect if a serial console is attached.
-ethan