Look for "bulging" electrolytic capacitors in the secondary stage.
Ensure the chip is receiving its dual or single supply rails (usually +14V and -14V , or a single +24V rail coming directly from a secondary pin of the Flyback Transformer). panasonic tc-21rx20c circuit diagram pdf
You can find the Panasonic TC-21RX20C circuit diagram PDF through various sources: Look for "bulging" electrolytic capacitors in the secondary