In this video you will see a 900w class d repair tips. this types board are came with inbuilt bias arrangement. but when bias control zenner diode get fail{open}, it will kill all ic, MOSFET and it's related components. if you are going to repair it by blindly replacing the burn components.it will burn again and again .
the result will be only financial loss only.
![](https://i.ytimg.com/vi/aLpfkFSXDSM/maxresdefault.jpg)