82. The phase locked loop circuit in an MF/HF receiver appears to be faulty. What is the most likely cause?

A non-functional Voltage Controlled Oscillator (VCO) prevents a phase-locked loop (PLL) from operating, making it the most likely cause of a PLL failure. The PLL relies on the VCO to adjust frequency; the Automatic Gain Control (AGC), Beat Frequency Oscillator (BFO), and Intermediate Frequency (IF) filter are separate components that do not directly affect PLL operation.