My Sharp LC-40FG2241KF with a TP.MS6486.PB711 mainboard has a failed LED boost converter. The FET (AOD458) was s/c and the rectifier/blocking diode (SR320) was also s/c. Both were changed as well as the input and output caps.
On powering the TV we get 55v on the LED rail. Immediately we take the TV out of standby the controller (OB3350CP) starts to trigger the Gate of the FET and it dies again (with smoke no less). The inductor is incredibly low resistance at 0.09 Ohms and I suspect it is short and so the FET is directly grounding the 55v supply, but I may be mistaken. Scoping the Gate without the FET installed reveals a pulse of a few uSecs so I think it is been driven correctly.
Additionally, the SR320 also dies again so maybe it isn't the inductor as I can't see why that would kill the diode when the current is flowing through only the FET.
The TV's had valves when I first started repairing them so things have changed a lot and I would appreciate any advice on the new wizardry. I can't find the correct schematic online and that would be a great help.
Thank you everyone...
On powering the TV we get 55v on the LED rail. Immediately we take the TV out of standby the controller (OB3350CP) starts to trigger the Gate of the FET and it dies again (with smoke no less). The inductor is incredibly low resistance at 0.09 Ohms and I suspect it is short and so the FET is directly grounding the 55v supply, but I may be mistaken. Scoping the Gate without the FET installed reveals a pulse of a few uSecs so I think it is been driven correctly.
Additionally, the SR320 also dies again so maybe it isn't the inductor as I can't see why that would kill the diode when the current is flowing through only the FET.
The TV's had valves when I first started repairing them so things have changed a lot and I would appreciate any advice on the new wizardry. I can't find the correct schematic online and that would be a great help.
Thank you everyone...
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