Stop spinning i can't get my turntable to turn off unless i unplug it. as soon as i plug it back in it starts spinning automatically. why can't i turn it off?

Probably, unless the 'fully automatic' switch is faulty. Buy the belt, unplug it the day before so it loses any memory, replace the belt and plug it back in.

$17.90 for a new one

https://www.google.com/search?safe=off&rlz=1C1QJDB_enCA643CA644&sxsrf=ALeKk02Ybc3H0TEoy9KswAcEtPECXEoMog%3A1614472179612&ei=8-M6YMflJOic_QaHoLOADQ&q=mcs+turntable+belt+replacement

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see if this link helps you out. Tips for Repairing Your Home Turntable ..
or this one.. JVC AL E31 Turntable doesn spin automatically Google Search

Don't try and force anything that won't move. Try this. With the power unplugged, place the tonearm over the record, if it will move freely, while rotating the platter by hand. Move the tonearm slowly over the surface of the platter until the end. Continue turning the platter by hand and see if the tonearm picks up and returns to the rest. See if that fixes your issue. For more information or further questions, please visit my website at audioserviceclinic.com. Thank you.

Hi, with the tone arm sitting on its mount rotate the platter manually approx. 12 times. That should reset all the auto functions. Cheers john.

Move the tone arm to the center and back. If it still keeps running, it's a service item.

hi,
from ur narration i think the ur turntables belt have some problem.it may be become loosend. if not put the belt correctly. first insert the belt on the round circle underside the plater( metal table). the put it on the turntable by pulling the belt with ur finger through the hole on the platter , engage the belt with the motor pully( brass spindle ). then plug it and try .
ok

One suggestion i would make is that in the microwave there is the turntable, lift the plate off ,then below it you will see a circular object with wheels on.I think you may have this the wrong way up, so turn it over put the plate back on top and should work.

its the circular piece on runners that is the problem

Look for a switch that has 33 and 45 unless the hole in the middle of the record is rather large turn it to 33.

2 THINGS COME TO MIND--A BAD ELECTRONIC CONTROL PANEL (BEHIND THE KEYBOARD) USUALLY FROM A POWER SURGE,,,,OR A BAD SOOR SWITCH--THIS REPAIR WOULD NEED A TECH--TUNICA