Cross-talk square-wave?

[dwight]

270K is not a transmission line load.

As I recall ribbon cable is around 100-150 ohms

impedance some place.

The signal does look nice and square.

I doubt is is inductive coupling, with that high a

load, I'd say it was capacitive.

inductive coupling requires current flowing.

Dwight


________________________________
From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Al Kossow via cctalk <cctalk at classiccmp.org>
Sent: Wednesday, March 29, 2017 2:35:54 PM
To: cctalk at classiccmp.org
Subject: Re: Cross-talk square-wave?



On 3/29/17 2:14 PM, David Bridgham via cctalk wrote:
> And I think this picture is the smoking gun.
>
> http://pdp10.froghouse.org/qsic/pic_24_2.gif
>
> Again, the bottom trace is the CS signal in question and the upper trace
> is now one of the QBUS DAL lines (after the bus transceiver and level
> converter) that's running across the ribbon cable near the CS signal.
> It does appear that induction can make a fairly clean square wave.
>
>

simple thing to try is split the ribbon cable between the two signals