With the Kenmore series 80 Dryer plugged in, Pressing the start button causes the motor to hum as if the belt, pully or motor is frozen. The drum doesn't turn during the humming and is difficult to turn when machine is unplugged

Sounds like a weak motor. You'll have to get a new motor installed. They are fairly inexpensive and easy to install yourself on that type of machine if you are handy. Motor is located in the bottom right of the machine, attached to the drum belt through a small pulley underneath the drum next to the motor.

If your dryer doesn't tumble, check these: Belt Motor Door switch Belt Dryers have a drive belt that turns the clothes drum. If the belt breaks, the drum stops rotating. Then you need to replace the belt, and often the idler pulley, because the pulley tends to wear out at the same time. Click here for a belt installation diagram Motor If the dryer motor only hums when you press the Start button, the motor may be burned out. Here's how to test the dryer motor: Remove the belt. Check for obstructions in the blower fan housing. Manually rotate the shaft of the motor. If the motor is very stiff, or impossible to rotate manually, and the blower fan housing is clear, you need to replace the motor. If the motor rotates freely, run the motor momentarily with the belt removed and the blower in place. If the motor runs fine with the belt removed, there may be a problem with the idler pulley or the clothes drum. Try to rotate the drum by hand. If it is very difficult to move, correct any problem with the rollers or pulley, and then reassemble the dryer and try it again. If the motor hums but doesn't rotate on its own even with the belt removed--yet you can turn it freely by hand--you usually need to replace the motor or the motor start capacitor. Door switch Your dryer can't operate at all if the door switch is defective. It's inside the dryer main housing near the door frame. Sometimes you need to raise or open the top or front of the dryer to reach the switch. If it's defective, you need to replace it.
Thanks for choosing fixya...Regards, Joe

The bottom of the belt goes straight from the drum to the motor.  The tensioner goes on the top portion of the belt.

motor running but drum not turning, good chance drum drive belt is broken or has jumped off drive pully.

UNPLUG POWER CORD TO DRYER.
open dryer and look for broken belt, if belt is broken use modle number from dryer to purchas the correct belt for dryer install belt and reasmbele dryer. reconect power and test dryer.

the motor is more than likely bad but just to be safe check the blower wheel and make sure there is not anything in it then remove the belt and try to turn motor if the motor feels real tight then you need to replace the motor

You are correct in thinking its the belt, that is the likely culprit, although it could be the motor, but usually the motor would give some warning before going out...humming, slowing, etc. In order to get the front panel off, you will have to first get the top off. (The top snaps over the front panel).

when you try to start it again do you hear a humming comeing from the motor? can you jump start it by turning the drum while holding the start button? If you say yes to these questions you have a bad motor.

Hi, Does the dryer only hum when you push the start button?
Might be a bad motor.
Does the motor hum but, the drum doesn't turn?
Please let me know and get me a model # so I can assist you further.

Vic

Hello Friend, Replacing a dryer belt is very simple. Just remove front of dryer cabinet. unplug wires from dryer door switch. Just slide a new belt over the drum with the belt grooves facing to the inside. Underneath drum you will see a tention wheel next to motor. Install belt around tention wheel and around motor shaft pully. Re-install front dryer cabinet. Make sure to plug in the wires to the door switch and make sure that the drum is re-inserted back over the felt glide on inner cabinet front. Happy to help, Tim.

how about the idler pully that keeps the belt tight did you see it in there has to be there look if its is ther try to turn the drum by hand a foregin object could be jaming the tub im here to help get back and let me know