Turntable problem question

I have a Technics 1200 turntable.

My on/off knob (the round one) on one of my tables broke... the black top piece somehow came off is this just a matter off heating/sodering back to the insdie or did something break or what?
You didn't tell us exactly where it broke. If it is just the plastic knob, then you can just replace that(assuming the knob is available separately). If the shaft broke off, or the switch came apart internally, then you need a new switch, and this will have to be soldered, probably. If the switch broke in the "on" position, and you don't want to fuss with it, you can get a power strip with a on/off switch on it, and use that to turn it on/off. Check with member name "Psychicanimal". He is a SL1200 fanatic, and probably knows all about what to do to get it fixed up.