I know this is an old thread, but I thought I would post this fix for anyone else running into this problem, as most replacement boards are out of stock or cost way too much on eBay.
For those of you with a 2 blink led code, random resets, or other power board codes (can also trigger backlight codes due to voltage problems as these parts fail) here is a common fix that worked for my set when the power board went down.
2 blinks indicates power board fault. The failing parts are power MOSFETs. I fixed my board by replacing MOSFETs Q6101 and Q6102 (replacement part FQPF9N50CF 9 amp, 500 volt can be ordered via mouser) and fusible resistor R6536 (0.47 ohm. 1/2 watt ordered from amazon) on the power board. Be sure to reapply thermal compound when securing to the heat sink. The MOSFETs fail and the resistor blows to protect the rest of the circuit. This fix works on ex500, ex600, nx800, ex700, nx700, ex701, ex710 series sets and others, and is a common failure, the board locations and numbering will be different for other power boards but the same parts fail on many of these sets.