Hello there,
I have followed your thread with great interest.
I having the same problem with my Sharp 40" TV.
The TV runs for a few minutes, then turn off,the triangle blinks 2 slow and 1 fast.
I measured this device PC7703 with my Fluke and with reference to the other optocoupler and I didn't find any differences.
Do you remember if your faulty op/co was shorted or shows different measure.

Please advise
Regards

Nataf