Panasonic Tc-21rx20c Circuit Diagram Pdf [patched] -

The diagram will list specific voltages (e.g., 140V, 24V, 5V). Use these to narrow down which component has failed.

— This is the most complete schematic source for this specific model. Scribd (GP41 Chassis Service Manual)

The circuit diagram is vital for several standard procedures:

If you tell me the your TV is showing, I can help you identify which components on the diagram you should check first.

Trace AC mains input through the bridge rectifier to the switching transistor (usually a MOSFET like 2SKxxx). Identify test points for B+ voltage (typically 110V-115V DC).