Smart 82" Royal TV - Dead Power Supply Resurrection (September 2025)
Smart 82 inch Royal TV main board showing power supply section
Failed optocoupler location and replacement
High ESR capacitors replaced for stability
Massive 82-inch HDTV. Completely dead. Customer said it just stopped working one day.
These large HDTV models have substantial power supplies. When they fail, there's usually significant component damage.
Initial Diagnosis
Opened it up. Power supply board looked clean, no obvious damage. Started testing voltages. Nothing. Zero volts on all rails.
Checked the fuse. Good. Checked the bridge rectifier. Good. So the problem was downstream.
Systematic Troubleshooting
Started checking components systematically. Found a failed optocoupler in the feedback circuit. These are common failure points in switching power supplies.
The optocoupler provides feedback from the output to the controller. When it fails, the power supply won't start.
The Repair
Replaced the optocoupler (PC817). Also replaced several electrolytic capacitors that were reading high ESR: - 3x 1000µF 25V capacitors - 2x 470µF 35V capacitors
Used 105°C rated capacitors for all replacements.
Testing and Verification
Powered it up carefully. All voltage rails came up correctly. Let it run for several hours under load. Rock solid.
Checked all voltages with a multimeter. Everything within spec.
Lessons Learned
On large HDTV models, the power supply works harder and runs hotter. Components fail faster. Always check optocouplers and capacitors first.
This 82-inch TV is now working perfectly. The customer saved thousands by repairing instead of replacing.