qw3858 is a power chip
1. The qw3858 can be replaced with UC3842, UC3842A, etc.
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2. The package type of these chips, each pin function and parameters are exactly the same, can be directly replaced. In general, directly replace a uc3842, ensure that the mos does not break down, disconnect the gate, power on, multimeter test the uc3842 pin 6 has a swinging voltage, so that the basic installation is successful.