Debugging item: PR-8208

Countermeasure analysis and solution description

1. Shield the transformer with copper foil and link it with primary earth wire. 

    Add a small ferrite bead to every pin of the bridge rectification, the middle pin of Q2/Q3/Q6, as well as each of the two pins of D3.

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2. To AC input end, add a filtering circuit consisting of a 0.33uF X capacitor + two 200uH differential inductors.

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3. Contact a 151T ferrite bead in series to each of the five diodes shown in the picture, 

    and add a 100pF capacitor between earth and each signal wire of the output terminal.

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4. Add a ferrite core to each of the two AC lines, threading directly.

    Add a ferrite core to each of the two signal lines, winding one turn.

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5. Contact a 221T ferrite bead in series with negative pole of the diode shown on the display board.

Testing data after debugging

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