Atex PDP-11/34

[cruff]

If you have an oscilloscope, that would give you a lot of flexibility in problem solving. If not, can you get ahold of some type of RS-232 breakout box with LED indicators, or something like I bought years ago RS-232 CHECK TESTER, that could work to determine if there was some signal activity on a port. The only problem would be if the amount of data being written to the port was small, you might need a slow motion video to detect the LEDs blinking

 

[KC9UDX]

Instead of LEDs, a connection to a dumb terminal can be very helpful.