KM-11 (was RE: help needed: problem with UNIBUS access on my PDP-11/70)
> 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 - 04:29:01 BST
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