TK RD-II SR intermittent operation

[trammd]

Got an RD-11 SR that is starting to not power up the Microprocessor and cab mounted remote control. There is Power to the Interface board, all fuses good, Fuseable link good etc.
After changing all the units drive belts upon powering on the Microprocessor switch I would receive no power to the remote controller when trying to start the unit.
I cleaned the terminals on the corroded switch and the switch harness plug and thought that fixed it, Unit started and ran fine for a couple days. No alarms USC good etc.
Now I go to turn on the unit and same trouble. No power to cab controller.
Any ideas on how to further troubleshoot?
I checked interface board for any loose harness plugs etc but all looks good except for the fact that no power to processor and cab control when the switch is cycled on.
Any help is appreciated.