Sharp LC-40N5000U Dead No Standby

This TV had no front LED and no standby voltage. The main fuse was not blown but U807 was shorted. R818 also had visible damage and measured open so it acted as a fuse. U808 was marked CS8N65F (NCH, 650V, 8A) and is the main switching FET for the PFC circuit. I subbed it with a 450V part since 650V is overrated. R818 is 0.39 ohm 1W. With both replaced, the leg of C822 (100pf 1KV ceramic) burnt up when I plugged it in. There was also damage to N834. N834 is marked 1271A and is a PWM controller NCP1271 still available at Digikey. I have ordered both parts and a replacement board. Power supply is HLL-4255WJ.

Here is a parts list

U807 CS8N65F sub FDPF8N50NZ (NCH, 500V, 8A)
C822 – 100pF 1KV
R818 – 0.39 ohm 1W
N834 – NCP1271A NCP1271D65R2GOSCT-ND‎ Digikey

I have encountered a similiar problem in Insignia model NS-48D510NA15 which uses a similar power supply design HLL-4855WC. I found the same FET shorted and the PFC only partially on. I suspected a bad N834 IC in this board as well.

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