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 Post subject: AMI F120 Gripper Motor Not Spinning
PostPosted: Jun Thu 30, 2016 4:17 am 
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Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
Hi,

I recently purchased an AMI F120 Jukebox. It ran for a bit then stopped grabbing records. I think I have it narrowed down to the gripper motor not spinning. I tested and it's getting power to the motor.

Despite the gripper motor having power could there be a switch or fuse that I'm missing thats not allowing the motor to spin? I did open the motor and the oil was old and crusted. I cleaned it up and added new oil but it will still not turn by hand. Looking for any suggestions on what to do here. Thank you.


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jun Thu 30, 2016 6:02 pm 
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Joined: Feb Sat 06, 2016 1:47 am
Posts: 2140
Location: Santee Calif. 92071
If it has power the switch is okay .. Not turning by hand there must be something binding the armature inside the motor .. Remove armature check for loose magnet or field coil ..


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jun Thu 30, 2016 11:10 pm 
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Joined: Dec Sun 23, 2007 4:23 am
Posts: 453
Location: Livonia, MI
I just got my first jukebox this week after tinkering with a friends recently and in both cases the gripper arm non functioning was fixed with lubrication of two gears adjacent to the gripper arm as well as the gripper arm shaft. These are both RockOla machines so YMMV with your AMI, but from poking around the net, a lot of these problems are lack of lubrication of the gripper arm mechanism itself.


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jul Fri 01, 2016 11:14 am 
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Joined: Sep Sat 05, 2009 9:45 pm
Posts: 992
Location: Sun City, Arizona
Hi,
Congratulations on your new jukebox. A really fun toy. The AMI has a power supply to operate the gripper motor and the motor that moves the mechanism back and forth as well as other jobs. These are DC motors (turntable motor is AC). Sounds like your power supply is supplying current to the motor (mechanism moves back and forth)? If it does you have DC power. Unless someone has already serviced the power supply by replacing that silicone rectifier with a new full bridge rectifier your DC power may be very limited. If it has not been replaced it should be even if it is presently giving your machine DC power.

When you turn the motor are you doing it by carefully turning the armature? If you try to turn it by moving the gear that engages with the gripper bow it won't turn and that would be normal. Only turn it by carefully using a finger to move the armature. It will take a bit of turning the armature to move that gear. The gears, I believe, you have already cleaned and oiled. Probably, they would like a bit of grease better.

Will the gripper bow operate freely, by hand, when the motor is not mounted on the machine?

It has been many years since I owned a AMI F but they are a great machine (no such thing as a bad jukebox!). Probably people here who know much more than I will probably add to this. My memory is not too good on this stuff anymore. I do know a factory (reprint) service manual is a wonderful thing to have. You can try Victory Glass or Always Jukin for this. The CD/DVD manuals such as found on Ebay perhaps avoid; I have never heard anyone being satisfied with them.

A nice place to get info from people who have helped me over and over is the website Phonoland.

The first thing I do is verify every fuse is correct before starting any machine. You might find a 20 amp fuse (tin foil, bolt or anything) where an 8/10th amp fuse is specified. If the small but powerful amp has not been rebuilt (change capacitors mostly) that would be an important thing to do as well. The older AMI's used a lot of zip cord type wire. I would check that very carefully, the insulation is usually very bad and very dangerous. Cleanliness and lubrication is really important too for many mechanical parts.

Sometimes the gripper bow does "freeze up", lack of lubrication. It always seemed to me my Rockola machines were more prone to that. Several of those I had to use a bit of heat, after removing the gripper bow, to help get freed up. Those little DC motors need things all clean and lubed so they can do their job.

Have fun and when you do get it going you will enjoy it. Buy more jukeboxes!


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jul Fri 08, 2016 10:56 pm 
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Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
Thanks for all your replies. The bow does move freely without the armature in place. I test the continuity on the coils and the coil seems fine and tested at 14 Ohms. Has anyone experienced carbon brushes being worn out and not making contact to the coil? Could that be my issue? Here's an image of what it looked like when I opened it up.

Attachment:
motor_open.jpg
motor_open.jpg [ 202.91 KiB | Viewed 1637 times ]


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jul Sat 09, 2016 12:07 am 
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Joined: Feb Sat 06, 2016 1:47 am
Posts: 2140
Location: Santee Calif. 92071
It sure looks like the carbon brushes are worn out and not making good contact with the commutator. You can make your own brushes By using a cheap D cell carbon battery. Split the battery open by the side seams. Remove the cap and bottom. The center core is made of carbon and will slide out. You can now work with center core with small files and sand paper to make the correct shape needed to fit back into the copper holders . The original springs can be used over again . A little trial and error to get the length right not to tight. Shape the carbon end that rides the commutator rounded so it makes the most contact. Clean commutator with fine sand paper to make smooth and round as best you can and get the old carbon out of the slots. I have done this with a few DC motors like that. Electric motors in car power windows.


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jul Wed 13, 2016 2:14 am 
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Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
Well, The motor brushes are back in the right place but I still cannot determine what is wrong. My possible next theory is the switches are out of order. I posted a video of the state of things. Thanks everyone for the help so far!

Here you can see videohttps://www.youtube.com/watch?v=80XA7qqorlQ


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Jul Wed 13, 2016 5:08 am 
Member

Joined: Feb Sat 06, 2016 1:47 am
Posts: 2140
Location: Santee Calif. 92071
You might be a little ahead of yourself with the gripper. The chain driven slider should first move into position then stop where the record selection was made. Only then will the gripper operate
and select side A or B .. All of this action is done with relays, solenoids and cam driven flex contacts. If you have the service information look for the area where the chain driven slide motor is activated from the plug in motor on back to contacts. Also I don't think you can turn the gripper motor gears by the output gear. I think is is worm drive and can only be turned by the input of gripper motor.


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Aug Fri 12, 2016 8:54 pm 
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Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
Thank you for the feedback. You are right on all accounts. I will keep digging further.


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Aug Sun 20, 2017 3:03 pm 
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Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
I have successfully returned power to the chain motor due to a freyed wire. Now we have the platter going to the correct positions. The Gripper motor then spins for a bit but on and off, puttering, then quits. Could it be worn out brushes and they are skipping?


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Aug Sun 20, 2017 4:21 pm 
Member

Joined: Feb Sat 06, 2016 1:47 am
Posts: 2140
Location: Santee Calif. 92071
Yes the carbon brushes are worn out. They are too short to make a good contact. Can make your own as said in early post.


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Aug Sun 20, 2017 4:36 pm 
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Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
Thank you. Do you know how long they need to be? Maybe buy NOS somewhere?


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 Post subject: Re: AMI F120 Gripper Motor Not Spinning
PostPosted: Nov Wed 22, 2017 6:14 pm 
New Member

Joined: Jun Mon 20, 2016 4:13 am
Posts: 11
I discovered a broken wire below the jukebox junction underneath the entire plate, it had rubbed off. Once I fixed this it would run the track again. Then I replaced brushes on the gripper motor and that started working again. So now it is retrieving records and placing them on the platter. But once that happens i loud knocking starts. You can see it in this video https://www.youtube.com/watch?v=mesDWIXd0aM


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