Yes the turntable motor can be replace.
To obtain a motor do a search for:
"MICROWAVE TURNTABLE MOTOR TYJ50-8A7"
To replace motor:
0. Unplug the microwave from the mains.
1. Take out glass plate and plastic wheeled ring.
2. The plastic top to the motor rotor will pull off quite easily.
3. Turn microwave on it's side.
4. You'll need a hacksaw or metal snips to remove the motor cover. This may sound drastic but it's designed for this and can be fixed back in place by rotating it 180 degrees.
5. Remove the two spade terminal that power the motor making a note of which colour cable goes to which terminal.
6. A single screw holds the motor in place - remove this and then the motor.
7. Take new motor and reverse the process.
Good luck.
Graham
November 2011