That is right, there is a TL431 on the secondary side, attached is a fuller schematic. But the heavier the load the louder the whine. I havn't looked at C609 yet. C608 is a tiny SMD ceramic cap. R611 and D608 were blown, I replaced them.
Edit: for completeness, the following parts failed: Q601, Q602, D608, R611, and D655 on the secondary side (shorted)