TKR-720/TKR-820 – How to Disable the Internal Controller - By Mark Tomany N9WYS

Remove the internal signaling unit. (I'm looking at the TX/RX Unit in the service 
manual, Page 83, and the Signaling Unit, Page 76.) Unplug both cables from the 
signaling unit and add the jumpers to the connector.

On CN6 of the repeater TX/RX Unit, or at the cable connector end for CN1 of the 
Signaling Unit, apply jumpers to pins 2+3, 8+9, and 10+11. Here are the signals:

Pin 2 = PTT, Pin 3 = KEY; Pin 8 = AFD, Pin 9 = DET; Pin 10 = AC, Pin 11 = GND
 
If the external controller crashes, you can plug the internal one back in and 
still be operational. If the external controller is wired CORRECTLY to the 15 
pin accessory plug, it WILL work properly.

I've used solid copper 24ga telephone wire to short the connections, secured 
with black tape. My personal preference was to insert the jumper wires into CN1 
connector at the Signaling Unit end of the cable. To reverse the modification, 
all one needs to do it remove the jumpers and plug the Signaling Unit back in.

NEVER use the internal controller with an external controller. You are just 
asking for problems.