Phase Lock Loop Troubleshooting
If one of the phase-lock error messages appears, a loop has failed. Start the troubleshooting procedure by determining if the malfunction is dependent on Center Frequency, Frequency Span, etc. Next, break the suspected loop and measure the power levels as indicated on the RF Section Analog Block Diagram. Even with the oscillators at the extremes of their ranges, the power levels must be within the limits indicated. The loop frequencies can be counted and compared with the programmed frequencies listed by KSR by inserting a tee connector into the loop.
The Lock Indicator Disable jumper (A12TP2 to A12TP3) may be necessary if the keyboard is locked out. Use the information from the Diagnostic Function and the Start Frequency Tuning Equations to narrow the fault to a single assembly.
