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Sota Sapphire Disassembly
Sota Sapphire Disassembly
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Old 27th August 2017, 03:36 PM   #1
wanders is offline wanders  United States
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Default Sota Sapphire Disassembly

A friend has a mid-80s Sapphire, never serviced, that he'd like to sell me. It's got a noise associated with the motor. I've got it on my bench for inspection. Some of the time there is no noise, but if you move the table it can start up again. Sometimes moving it again will stop the noise, but usually not. Seems possible that the motor is ok and the noise is associated with motor mounting - bushings, etc. I'd like to open it up to inspect the motor area.

Right now the platter is snugged down by the transport screws. Knowing the Sota reputation for easily damaged bearings, I don't want to remove the platter. I'd like to find some other way to get a look. I suspect some of the screws on the bottom will release the black top surface board; or drop the thrust plate from the chassis. But I don't know which. I removed the aluminum plate that covers the pulley and control buttons. I removed the tonearm board. Easy enough to release the motor mounting plate from the top surface. Obviously Sota won't publish a service manual, or I could get the answer there.

Any thoughts?

Thanks
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Old 27th August 2017, 04:59 PM   #2
wanders is offline wanders  United States
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I want able, from the top, to work the motor assembly out of it's space without loosening the platter bolts. And I was able to fix the noise by twiddling the lower motor seating screw. But, there has to be an easy way to remove the bottom cover board to access that adjustment screw.

Again, experience appreciated. Thanks.
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Old 27th August 2017, 06:48 PM   #3
AVWERK is offline AVWERK  United States
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IMG_0352.jpg

IMG_0354.jpg

You can loosen the 4 corner screws and it should come out
The screw in the square adjusts the end play and when excessive, the motor starts making noise. If you have a way to measure the end play with a dial indicator, tell me what it is.
I posted somewhere this info about the tolerance and will have to check or just start reducing the play until the motor noise goes away, but make sure it has some movement

The platter assembly can be removed easily . Inside the base you see 2 screw holes that push against the rim area for transport. This pushes the bearing off the sapphire disc to prevent damage
This one a square mounting block and later ones are round, but the same design
There is a plate that locks the bearing/platter together to prevent the platter from falling out when turned over not shown.


Regards
David
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Last edited by AVWERK; 27th August 2017 at 07:10 PM. Reason: Add photo .
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Old 27th August 2017, 07:35 PM   #4
AVWERK is offline AVWERK  United States
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I have never needed to actually disassemble the motor from its sandwiched PCB board and I would not do so until you know the play is correct

I just measured the end play movement to be .007"

BTW- the bottom " cover " is the plinth itself that the platter bolts too. I can post a photo of that if you need it

Hope this helps

Last edited by AVWERK; 27th August 2017 at 07:38 PM. Reason: .
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Old 27th August 2017, 07:54 PM   #5
wanders is offline wanders  United States
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Thanks for both replies. I got the assembly out just the way you recommend; I thought there might be an easier way. Not sure how or where you would measure tolerance. My motor has the square seat and has a set screw at the bottom. I had to remove the set screw all the way then reinsert it before I got the motor to quiet down.

I'd appreciate a pic of the plinth assembly. It's little mysterious. I noted how precisely the arm board fit and wondered in the top black surface might be not attached to the oak plinth - maybe secured by some screws up from the bottom.

Thanks again
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Old 27th August 2017, 08:09 PM   #6
AVWERK is offline AVWERK  United States
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The plinth "hangs" on springs from the outside structure
I numbered all 4 spring locations. It is somewhat difficult to reattach and pull back the springs to attach the nut to each spring set, but doable
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Old 27th August 2017, 08:41 PM   #7
AVWERK is offline AVWERK  United States
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To measure the pulley you must measure from the top silver plate to top of motor pulley and notice how much freeplay you have. You could use calipers as most don't have a magnetic base/ dial indicator just laying around.

The only way to seperate the top from bottom plinth is to remove all 4 spring screws and the 3 adjustable feet

While your at it, remove the plate the keeps the platter/bearing together and look at the shaft. Excessive wear will not pass the finger nail test- if you feel the ridge it has wear dispite how it might look.

A call To SOTA a few years back mentioned they used Tuffoil lubricant. 2 drops per bushing.
Mine is the vacuum version. This seemed too little, but a youtube video asking this very question and the same size bushing showed when heated to an extreme- only 2 drops came out of each.

Regards
David
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Old 20th June 2020, 04:44 AM   #8
bbww is offline bbww
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Hello David,

How can I remove the platter to access the bearing? My table is making noise in every revolution. Do I just push the two hex set screws up to separate the platter from the bearing? Is there other procedure before removing the platter?

What kind lubricant should be used for the bearing? Please kindly advise. Thanks for your kind attention.

Regards,
Will
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Old 20th June 2020, 02:40 PM   #9
AVWERK is offline AVWERK  United States
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Just sent a PM to you
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Old 21st June 2020, 11:32 AM   #10
hirscwi is offline hirscwi  United States
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Sota Sapphire Disassembly
I had a SOTA with a similar problem. It was the motor. Ruston part of the armature was rubbing the PCB that is sandwiched between the two case halves. It's possible to drill out the 4 rivets that hold the motor case together. Carefully. Then separate the halves and you can clean up the motor inside. Four small screws can put it back together. There's not much clearance so it doesn't take much to interfere and make noise.
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