First off, here is the link to the capacitor I replaced--it'll set you back about 15 USD. It's a 60 Microfarad 220V 60hz garage opener capacitor.
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Here is an Amazon link for a new Liftmaster MJ5011u: or MT5011U
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If you hear the motor humming, but nothing turns, 8 times out of 10, this will fix the situation--same goes for external AC units.

The Lowdown: I was tasked with troubleshooting and trying to repair a warehouse overhead garage door operator that won't open and was not turning or working as expected. This commercial jackshaft opener was first installed in 1992 at the brewery where I work as a facilities maintenance tech, but no one who works here now can remember it working.

The original manufacturer was Link Controls Inc, and this industrial model was the MJ5011-B2, which I couldn't find any manuals for, but I think they have since been sold to the company that manufactures and sells LiftMaster commercial-grade garage door openers. I found a similar model, the MJ5011U and downloaded the PDF manual from a website called Chamberlain, I think, and just about everything looked exactly the same as the older unit. [ Ссылка ]

When I pushed either the open or close buttons, the motor would just hum, but the solenoid which turned on an electric brake would operate, so I knew that power was being supplied to the unit. I remembered from a previous air conditioner repair that a bad start capacitor can keep a motor from being able to start. Turns out the capacitor in this roll up door unit was bad, so I changed it out with another one I had on hand. When I did that, the motor turned right on.

The next thing I needed to replace was the drive belt oh, and the manual for the MJ5011U recommended a 4L290 v belt, I also bought about 10 feet of #41 roller chain which would run from the output sprocket to the spring shaft of the garage door.

Once I had all of that sorted and working, I had to perform an adjustment on the limit nuts which travel back and forth on a screw and activate limit switches which represent the open and closed travel of the garage door.

I think this is a pretty standard designed for most large industrial warehouse garage door openers from the 90s and even up until today, so I hope some of this will help you if you had a similar problem!

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