This is what I found so far, I have to leave it for a while, but there should be enough if anyone wants to pursue it further.
The RS232 connection is:
P6 ---9pin Dsub
1 -----2
3------5
5------3
The original Tandy100 was set up just as a dumb terminal mode.
I tried some of my Modem programs and found that Telix had the VT52 emulation.
I did not try all the others, I think if I spent time I may get one of the others to work.
I did get some spurious characters on the screen but it did not seem to affect anything, it takes a bit of practice to change the variables.
Only change jumper P10 when the power is off.
The protocol has to be set to 9600 N 8 1.
I tried ANSI.SYS in the Config.sys file, but it did not make a difference.
I had nothing connected so when I switched on the amp, the Status screen stated that the thermal switch was open.
After jumpering it out, the two red status LED's went out.
The status screen only registers on power up.
You will probably need a Win98 or earlier PC and run at the DOS prompt.
I did not even try Hyperterminal, I have found it pretty useless anyway as a Modem program.
Nosmo.