[Kantronics] HELP - Kantronics KPC-2

[John Hagle]

Hi. I am trying to re-establish my packet station circa 1990. And after 
a month or so, the KPC-2 has stopped communication back to the computer 
in terminal mode.

The screen did display the TNC power on message, but no computer keys 
would send anything to the TNC. No <ctrl C> response, or response to any 
of the Kantronics commands. I did a hard reset internally, and now I get 
only the expected power message of "press (*) to set the baud rate - 
with no results. There is still no communication from terminal to KPC-2.

I swapped out the serial cable. Same trouble.

I have checked the internal TNC voltage regulators (+5 and -5 VDC) and 
both voltages are present without any significant ripple.

I have checked the logic gates in the SN74HC14 chip and in the TC4030BP 
device and the static (with voltage applied) conditions agree with what 
I would expect from looking at the truth table for the devices.

I am not too sure of my understanding of the DTR, RTS, TXD and DSR 
signals between the computer and the TNC.

Is anyone familiar with common failures in TNCs of this vintage, or 
could help me with trouble shooting techniques so I can repair it at 
home. PS: i have not ruled out problems in the computer serial port yet 
either.

Thanks in advance

John R. Hagle
de N2JH
Ripley, NY