> -----Original Message----- > From: Paul Koning [mailto:paulkon...@comcast.net] > Sent: 24 August 2016 17:59 > To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts > <cctalk@classiccmp.org> > Subject: Re: MicroVAX II Console Garbling Characters > > > > On Aug 24, 2016, at 12:21 PM, Rob Jarratt <robert.jarr...@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 they > are, then the fact that it depends on power suggests your RS232 interface is > 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. Thanks Rob
