Printed circuit board with mounted electronic components

TV power supply board

The power supply board makes a standby voltage that is always on, then switches on the main rails when the main board sends a power-on signal. Check standby, then the power-on signal, then main rails. The primary side holds a high-voltage charge.

Cross-checked ~45 min advancedBrands: All

Before you start

The large primary filter capacitor charges to roughly 1.4 times line voltage (about 170 V DC on 120 V); discharge and verify before touching
Live-voltage tests: use a CAT III-rated meter, insulated probes and one hand; keep the other hand away from the chassis
Keep one hand away from the board; primary side is not isolated from the line

Diagnostic steps

Unlock all 5 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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