KM-11 (was RE: help needed: problem with UNIBUS access on my PDP-11/70)

From: Gooijen H <GOOI_at_oce.nl>
Date: Fri Jul 12 03:58:00 2002

Hi all.

> BTW, how much did that KM-11 replica PCB cost? I wish I
> could find hobby-level PCB vendors that _could_ do
> gold fingers, but for as much as that card would be used,

I did a quick check in my cards stock.
I guess that the simple M105 address selected is a cheap
candidate to get a new life as KM11. Just remove the few parts
and, to be sure there are no interconnections, cut the trace
a bit after the fingers.
Then solder a flat cable to the traces that are used for the
KM11. ** Do not extend the length of the flat cable too long!

Stray capacitance between the wires can induce a voltage
in the wire next to it. I had that problem a few years ago.
The thing worked nice, but after a few months it died on me
and I could not figure out what went wrong at first.
With the oscilloscope the problems became visible: due to
crosstalk/induction between the wires, the signal voltage on
some wires went negative, more than -0.6 Volts.
TTL circuits really hate that!

- Henk.
(with a busy weekend ahead...)
Received on Fri Jul 12 2002 - 03:58:00 BST