Date   : Wed, 18 Jul 2012 21:10:04 +0100
From   : walker_matt@... (Matthew Walker)
Subject: RS423 won't transmit. Dead 6850?

I've a plain Issue 7, which can't transmit anything from the RS423 port.
It can receive fine (just *fx7,6 *fx 2,1 then type stuff on a PC)
Sending however, nothing. I tried sending stuff with *fx5,2 then *fx8,6
but nothing appeared at the PC end. I know it's not the cable at fault
so I tried swapping the serial ULA, which made no difference. I had a
look at pin 6 of IC4 the 6850 ACIA, which is permanently high regardless
of weather the ULA was in place or not. I'm assuming that the 6850 is
dead, but seeing as it's soldered in and will be a pain to remove, does
anyone have any ideas I could try before I have to de-solder the 6850?