Just got back function of my nice old Kenwood stereo (lovely addition to a television/DVD/BD setup, the sound is excellent). During snow season, with power flickering, it... got very odd. Powered up, but wouldn't take any remote commands.
Everything in the schematics available was OK, but the switchmode power board is completely absent from the circuit diagrams.
Main power functions go through a KA1M0380 four-pin power IC. Fairchild (before they sold out to ON) made it, but it's not now available, except for small batches sold on eBay... Snow-laden branches interrupting power WAS happening right before the unit stopped working, so... replacing that chip was indicated. That fixed it.
The only clue to the fault, was the wonky power in my neighborhood.