MicroVAX II Console Garbling Characters

Rob Jarratt robert.jarratt at ntlworld.com
Thu Aug 25 03:08:24 CDT 2016

> -----Original Message-----
> From: Paul Koning [mailto:paulkoning at comcast.net]
> Sent: 24 August 2016 17:59
> To: rob at jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
> <cctalk at classiccmp.org>
> Subject: Re: MicroVAX II Console Garbling Characters
> > On Aug 24, 2016, at 12:21 PM, Rob Jarratt <robert.jarratt at ntlworld.com>
> wrote:
> >
> >> Incidentally, the terminal and the machine *were* plugged into
> >> different sockets, but now they are connected to the same wall socket
> >> and the problem persists.
> >>
> >
> >
> > Actually, since connecting terminal and machine to the same wall
> > socket, the garbling seems to have much reduced, but I do get lots of
> > dropped characters all the same.
> Check that the shield ground and signal ground are both connected.   If
> are, then the fact that it depends on power suggests your RS232 interface
> inadequately designed.

It turns out the problem was the cab kit. I replaced it with a spare and the
machine worked great. On closer inspection I found some corrosion and
possible evidence of a previous battery leak, so I am going to take it
apart, check it and clean it up.

The other thing that made me suspect the cab kit is that the act of pulling
the serial cable out (not unplugging the terminal) would cause the machine
to reset. MicroVAX II does this if you switch off the console terminal while
the terminal is connected.



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