Look for cold solder joints around the deflection yoke connector.
Test the B+ voltage (usually around 110V–140V) to ensure it is stable. How to Use the Circuit Diagram Effectively panasonic tc-21rx20c circuit diagram pdf
Use this for a bird's-eye view of signal flow from the tuner to the CRT. Look for cold solder joints around the deflection
If you have an oscilloscope, compare your readings to the printed waveforms to find signal distortions. panasonic tc-21rx20c circuit diagram pdf