Turn off AC power to Transmitter and install the control board on an extender card; once completed, turn on the AC power to the transmitter. With a DC Voltmeter check U19 pins 1, 2, and 8; all should be <1 VDC.
a) If pin 1 is >12 Volts, then either power supply #1 is defective or removed. Replace power supply #1.
b) If pin 2 is >12 Volts, the exciter is either defective or muted, the internal cabinet interlock or external interlock is open, the external failsafe is open, or the antenna interlock jumpers are set incorrectly. (If Pin 2 indicates the exciter is muted, check on exciter card TP5 with a scope for a saw tooth wave form using TP6 as ground. The PWM saw tooth wave form might be missing or is <5 VDC. If the PWM saw tooth wave form is <5 Volts, increase the level by adjusting R62.)
c) If pin 8 is >12 VDC, an external transmitter RF mute is applied to remote terminal.