I found two resistors next to the keyboard header on the CPU board. One was about 130 ohms to Ground, the other was about 120 ohms to +5V.
The other end of both resistors next to the keyboard header was connected on the PCB to the TX pin from the keyboard.
I unsoldered the end of the 130 ohm and 120 ohm resistors on the opposite side from the keyboard header.
I inserted a 1K ohm resistor into the hole where the 120 ohm resistor was connected to +5V and connected the other end of that resistor to the end of the 120 ohm resistor.
I didn't have to remove the CPU board for this operation.
This allowed my Parallax USB to TTL serial to work. This converter has female pins and I used Arduino breadboard jumpers to connect the serial interface to the LEMO pins.
From the front panel, the top left LEMO female socket is Ground - and was connected to the Parallax Vss pin.
The bottom left male pin on the LEMO is the TX pin from the keyboard and I connected it to the Parallax TX pin.
I could now type on the PC Realterm application (4800 8N2) and see the output on the red LEDs on the front panel.
I then typed two commands - from maddisassembler in 2016 "RE: 4041 basic program for redirection", but left off the line numbers and typed in immediate mode:
SET DRIVER "COMM0(BAU=9600,FLA=BID):"
SET CONSOLE "COMM0:"
I got an error message on the second command. The operators manual shows "SET CONSOLE "COMM:", so I typed that and that text stayed on the LED display - but my serial console was then enabled.
I guess COMM0 is needed if you have the second COMM port option. The 4041 I was using has only one COMM port.
I uploaded a photo of my simple mod. I left the two original resistors if I wanted to restore to original later.
/g/TekScopes/photo/247590/0?p=Created,,,20,2,0,0
Monty
