For Orion TV1334A. My case was similar except d509(18v zener) was shorted
making Q502 appear defective. Info on P5NC50FP is very limited. I used an
ECG 2385 and the insulator kit as a replacment because that is what I had.
R514(.22 ohms 1 watt) was open. R542 was open and could only make the
first color band to be blue. After some math I concluded the value must be
about 6.8 ohms (the set draws 54 watts most of those watts must pass thru
R542 so I clac. that the 2 watt resistor had .45 amps passing thru it and
determined that 68 ohms was too big and .68 ohms was too small to match
the wattage.) In this set R506 was 2.7k ohms.
The set is working and the supply is regulating. I repaired this TV for
myself and was not concerned about hazards created by using the incorrect
chopper fet. Precautions to insure safety from fire would make me order
the correct components when repairing for a customer.