SOTA Sapphire basket case/resto project....

dogwan

Dogwan
Sunday afternoons are turning out to be my best time for finding CL deals!

This week I spotted an ad for SOTA tt parts that was an hour old. Must've been the 1st response because $25 dollars later I had an early Sapphire with vacuum platter in parts. THANKS Marty if you see this!

So far looks fairly complete with the exception of the PS, dustcover, an armboard, clamp, and vacuum pump.

The speed selector switch is busted, but I think I can easily fix that.
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The biggest cosmetic issue is the Melamine (or is it painted MDF) top plate is busted up around the front of the cutout for the platter. I think that to fix this I will have to pull the flaked up portion and do an epoxy fill. Then do a careful job of masking, sanding, and then painting the top plate. Seriously, there is no way of getting that part out to replace. And, I don't want to get into trying to layout the springs and feet studs on a new top plate.
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There is also a big 'ol splice in the power cable. Looks like someone needed to pull the motor assembly and the wiring was glued into the corners of the plinth. So, they just cut around it and spliced it back together.

My big question is this: Can I just hook it up to my EICO 1030 regulated power supply to test the motor? Based up on reading there is a built in regulator on the motor board and it wants about 28vdc.

If the motor is working, would there be anything wrong with scrounging an old laptop power supply that puts out 28vdc and using that instead of shelling out $200 plus to SOTA? No offense to them, but I am currently doing a 4 mo. unpaid internship.
 
The bearing feels really good. Nice and smooth. Takes about a 60 seconds to wind down after hand spinning up to 33rpm. However, I am really worried about the sapphire thrust bearing and would like to inspect it.

I've looked for info on how to lift the platter on the vacuum models but couldn't quite figure it out. On top of the bearing block there is an open sided plate with 3 allen headed bolts holding it down. Is this the only thing keeping the platter from lifting off the bearing post?

I can't imagine that I would need to remove the banjo-bolt for the vacuum. But I did see reference to removing a bolt in the same location for non-vacuum models.

Help?

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You can plug that motor into a wall 110 outlet and test if it spins, also the speed switch.
 
The bearing feels really good. Nice and smooth. Takes about a 60 seconds to wind down after hand spinning up to 33rpm. However, I am really worried about the sapphire thrust bearing and would like to inspect it.

I've looked for info on how to lift the platter on the vacuum models but couldn't quite figure it out. On top of the bearing block there is an open sided plate with 3 allen headed bolts holding it down. Is this the only thing keeping the platter from lifting off the bearing post?

I can't imagine that I would need to remove the banjo-bolt for the vacuum. But I did see reference to removing a bolt in the same location for non-vacuum models.

Help?

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All three of these get pulled, then the platter will come off the sub chassie.

It would have ben best if the sub chassie wasn't removed from the plinth, as those springs are tunned.
 
You can plug that motor into a wall 110 outlet and test if it spins, also the speed switch.

No offense, but I wouldn't dare do that. Not only is there not an AC plug on this, but the caps on the motor board are only rated at 40v.

Re: not removing the sub-chassis, for $25 I wasn't going to bitch about it.

I would like to know how the springs are "tuned". Looks pretty straightforward to me with sub-chassis hanging from them. I don't see any mechanism for tuning other than balancing the weight on the sub-chassis with the lead shot. I'm not saying they're not tuned I just don't see how.
 
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These screws hold that retaining plate to keep the bearing together. I would not mess with it if it feels smooth.

You might as well know now SOTA will not sell you small parts to fix the table up. They will service it though, the vacuum pump is around $750.00
 
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Ahhh, so I can squeeze an allen key in there to remove the 3 bolt to get the retaining plate off and then separate the bearing to inspect? What is recommended for lube?

I have gathered that SOTA doesn't sell parts readily, which is unfortunate. I am pretty scrappy and better than average at mechanical solutions. My uncle (a retired Boeing engineer) has called me the best "barnyard engineer" he's ever seen. LOL.
 
No offense, but I wouldn't dare do that. Not only is there not an AC plug on this, but the caps on the motor board are only rated at 40v.

Re: not removing the sub-chassis, for $25 I wasn't going to bitch about it.

I would like to know how the springs are "tuned". Looks pretty straightforward to me with sub-chassis hanging from them. I don't see any mechanism for tuning other than balancing the weight on the sub-chassis with the lead shot. I'm not saying they're not tuned I just don't see how.

They have studs that go though the sub chassi then fender washers and nuts to pull the springs down.

Hey you don't have to listen to me on what to do or not, what do I know.
 
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I'm afraid my post lost something in the translation. That wasn't an indignant "I would like to know...". It was an honest entreaty to gain an understanding. Not intended to indicate that I was dismissive.

So, as a point of reference here's my understanding of tuning springs: Based on my experience of wading through a multitude of posts about tuning springs on AR decks (I currently have 4) there is a common misconception that adjusting the nuts and fender washers from the underside is "tuning" them. When in reality all that actually does is adjust the height of the suspension. The springs resonant frequency is a function of the compression of the spring and thus is only truly tuned by adjusting the load on the spring.

Applying the same principals to this application of springs(except it is now in tension instead of compression) I see how the threaded studs and fender washers function. But, since the sub-chassis is floating tightening the nut wouldn't actually "pull" the spring it would only adjust the height of the sub-chassis on the stud. Without changing the load (weight) I don't see how any tuning takes place. Another way of putting it is that there is only one point of contact that is not referenced against another point by turning the nut. Hopefully I've adequately explained my understanding of the physics and my confusion when you implied the tuning is now lost after removing the sub-chassis. If I am wrong I am all ears.

BTW, that is an awesome collection of decks. I hope I can get this one up and running enough to get a taste of what a SOTA is capable of.
 
I'm afraid my post lost something in the translation. That wasn't an indignant "I would like to know...". It was an honest entreaty to gain an understanding. Not intended to indicate that I was dismissive.

So, as a point of reference here's my understanding of tuning springs: Based on my experience of wading through a multitude of posts about tuning springs on AR decks (I currently have 4) there is a common misconception that adjusting the nuts and fender washers from the underside is "tuning" them. When in reality all that actually does is adjust the height of the suspension. The springs resonant frequency is a function of the compression of the spring and thus is only truly tuned by adjusting the load on the spring.

Applying the same principals to this application of springs(except it is now in tension instead of compression) I see how the threaded studs and fender washers function. But, since the sub-chassis is floating tightening the nut wouldn't actually "pull" the spring it would only adjust the height of the sub-chassis on the stud. Without changing the load (weight) I don't see how any tuning takes place. Another way of putting it is that there is only one point of contact that is not referenced against another point by turning the nut. Hopefully I've adequately explained my understanding of the physics and my confusion when you implied the tuning is now lost after removing the sub-chassis. If I am wrong I am all ears.

BTW, that is an awesome collection of decks. I hope I can get this one up and running enough to get a taste of what a SOTA is capable of.

Thank you
And in my opinion the best part about these decks is the suspention and lucky for you here the vacuum tables. Your deck was a Sapphire only then SOTA came out with the Vacuum Kit this is what you have. Then they came out with the Star Sapphire which is the decks that I have. Also you have a bit later bearing as it's round and not Square like my top photo.

Tunning
Even thought the sub hangs the adjustable stud efectivly shortens and leithens the spring, as such it's a tensioner.

I'll try and dig up info for you. I can delet my photos also if you want.
 
They have studs that go though the sub chassi then fender washers and nuts to pull the springs down.

Hey you don't have to listen to me on what to do or not, what do I know.

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I got five of them... well only four now since I sold the Sapphire that was taken apart.

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Apparently you know how to buy a compromised belt driven turd over and over and over, hey wait I'm sensing a pattern here.:D
 
Man, when you have that many of something you have to give a name to it, like "a college of owls" or "a gaggle of geese".
 
If you remember your Latin first declension nouns, then it is Sotae. However, if you want to talk about shoal of Sotas, you'd have to use the genitive, which would be Sotarum. If, on the other hand, you said you had to remove the plinth from the Sota, then it would be Sotis.

I'd stick to Sotas, myself :)
 
But really it's "State Of The Art" SOTA all capital letters a acronym.
 
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Ok, to get back on track....

I just looked and it's the Pabst GS 38.09 motor. (oops, that's Papst. Freudian slip from my youth) The Power cord is the thin gray one with a male DC connector. I assume that the center is positive and the outside of the barrel is the ground.

Unless someone tells me otherwise I am going to trace the center pin to the PCB and hook up the regulated DC output of my EICO 1030 and crank it up until I measure 28vdc at the output. Then I will turn on the motor unloaded at the power switch to see if the motor spins and if I hear any noise.
 
The motor in this thing looks identical to those in the HK ST-7, a Pabst brushless Hall device comutated DC motor afaik.
Chances are, that might be close enuff. Dunno.

Sent from my SM-N900V using Tapatalk
 
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