Ah, shorts are no fun. Neither is snapping a board off, which I have done and had to fix.
Electrolytic caps have a defined lifespan, and although some will last a very long time (and reform in use) by now the small ones (size and capacitance) are probably starting to drift seriously off spec. I did a recap on my KA-80 (the one I broke the board on) and found that some of the smallest caps were way off in both ESR and capacitance, a bad thing since some of them were coupling caps in the pre-amp section.
They are cheap enough to go ahead and replace them all. Use low impedance caps in all power supply applications, including the ones off the main power board (in my KA-80 there were separate lower voltage sections for the pre-amp, the driver section, and the phone pre-amp, some of which were fried). Use audio grade in anything that's directly connected to the signal path, and watch for non-polar ones. Use low leakage when applicable (it's nice to have a good list from the manufacturer when available, Kenwood does this in the service manual but Sansui does not). You can use higher voltage rated caps but do not change the uF ratings unless you know what you are doing and intend to have happen. Modern caps will be smaller than the ones in there so a higher voltage rating will fit in nearly all cases.
Main filter caps should be low impedance as well, with high ripple current ratings -- your choices are much more limited there.
I would not rely on the visual condition of electronics parts to determine functionality, use a tester for the transistors and diodes and carefully measure the resistors. Toss the caps (and a blown capacitor is very likely the source of the smoke!) and replace. Absolutely no point in putting iffy components exposed to a short circuit in contact with new parts until you verify they are good.
And use a dim bulb tester while troubleshooting -- it will save a lot of components even from shorts since the current draw is so limited.
