Peter do the
usual's:
Check SRAM voltage is above 2.8VDC
Continuity check RS232 cable.
Check RS232 IC has not entered sleep mode. See the FAQ's #11 for this.
I replaced a RS232 IC (as well as many others) on David's Gemini so it can be done easily, cheaply, as
a Last resort. It's more than likely the IC is in sleep mode.
Brendan