Date   : Fri, 20 Jul 2012 20:34:52 +0100
From   : walker_matt@... (Matthew Walker)
Subject: RS423 won't transmit. Dead 6850?

Interesting development. I've replaced IC 75, and that didn't fix the
problem although the new chip doesn't get mad hot like the old one.
Interesting thing is, after trying JHG's 'very very dumb terminal'
program the keypresses were echoed to the VDU. They were echoed to the
VDU even without the loopback, and even without the serial ULA in place.
Now I'm confused.