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Sota Cosmos restoration, or...

marknoir said:
And here’s the wear on the sapphire thrust plate. I’m not sure if it should be replaced or it’s still ok. This is a pretty strong magnification, stone plate is actually only about 3 mm in diameter.
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Another option might be to contact Steve Leung at VAS. He has done some bearing and thrust plate replacements (ceramic/sapphire) for other brands and may be able to help. He's also driving distance from you (right next to VPI in NJ).

https://vasnyinc.com/contact/
 
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I am not 100% sure of this, but I believe that in order to change out the sapphire bearing that SOTA presses out the spindle from the top.

If you look at pictures the metal of the spindle and the piece that holds sapphire disc are different metals than the platter. I suspect that it is one piece spindle and bearing cup, and press fit from the underside. It even looks like the diameter of the bottom side that holds the disc is slightly smaller than the bronze bushings.

Sooooo......I suspect that any decent machinist would be able to press the spindle out, and extract and replace the bronze bushings. Hell, I'd even be tempted to try it myself on a bearing press if I had access to the actual Sapphire disc.

I used to have some Machinist friends in Seattle who would have happily helped me out just to remove the mystery. Unfortunately, I didn't get my SOTA until after I moved to Portland.

Of course, any shop time at a machinist wouldn't be free and I know @marknoir is reaching his limit of his patience.

Again, the above statement is hypothetical.
 
Yesterday I bought a 1984 Sapphire motor. It’s the same motor as mine, but wired slightly differently. It’s pulley is about 1.5 times larger than mine, but it turns slower. Larger puller means that it is actually working harder than mine. I couldn’t just connect it to Cosmos control, so I used an outboard power supply. And wow figures went down right away! I could barely hear any. So my motor is kaput. Which gives me hope, yet again: if wow almost went away with this bearing, perhaps it will go down even more with rebuilt bearing. And better motor will certainly improve it even more.
Since I didn’t write it in the existing circuit yet, I couldn’t connect the vacuum. And what a difference! I can never listen to recotds again without vacuum. I think that a good clamp and perifery ring do give some improvement, but I doubt they provide this much improvement.
 
marknoir said:
Yesterday I bought a 1984 Sapphire motor. It’s the same motor as mine, but wired slightly differently. It’s pulley is about 1.5 times larger than mine, but it turns slower. Larger puller means that it is actually working harder than mine. I couldn’t just connect it to Cosmos control, so I used an outboard power supply. And wow figures went down right away! I could barely hear any. So my motor is kaput. Which gives me hope, yet again: if wow almost went away with this bearing, perhaps it will go down even more with rebuilt bearing. And better motor will certainly improve it even more.
Since I didn’t write it in the existing circuit yet, I couldn’t connect the vacuum. And what a difference! I can never listen to recotds again without vacuum. I think that a good clamp and perifery ring do give some improvement, but I doubt they provide this much improvement.
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Sounds like you are heading in the right direction. Can you just swap pulleys and then install it?
 
Mister Pig said:
Sounds like you are heading in the right direction. Can you just swap pulleys and then install it?
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Hi. There’s no need to change the pulley. This is an intermediate step. If the motor is the culprit, then the Eclipse motor/controller will fix this issue. For now I will try to wire this one instead of mine.
 
marknoir said:
but I would like to know how to remove these pulleys without damaging the motors. Also I need to find some info how to lube these Papst motors...
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On mine I just put a few drops of sewing machine oil (10w) at the base of the shaft and let it spin. Also, when I had the motor upside down to inspect and adjust the thrust bearing I put a few more drops at the base of the shaft and let it sit for a bit before re-assembly.

Can't say if that's a good approach, but I haven't had any issues.
 
marknoir said:
but I would like to know how to remove these pulleys without damaging the motors. Also I need to find some info how to lube these Papst motors...
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Mine is just a press fit. It came off without too much effort by hand. I didn't see any evidence of glue, but I didn't look too hard. I just put it back on. I kind of wish it was actually a tighter fit. It doesn't seem to slip though.
 
dogwan said:
Mine is just a press fit. It came off without too much effort by hand. I didn't see any evidence of glue, but I didn't look too hard. I just put it back on. I kind of wish it was actually a tighter fit. It doesn't seem to slip though.
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mine is pressed on really tight. I don’t want to damage the motor, so will leave it.
As to motor thrust, can it be unscrewed out completely to get access to lube the lower shaft bearing? Nothing will fall out of there? Thx
 
marknoir said:
mine is pressed on really tight. I don’t want to damage the motor, so will leave it.
As to motor thrust, can it be unscrewed out completely to get access to lube the lower shaft bearing? Nothing will fall out of there? Thx
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See post #70 on my Basket Case thread...
https://audiokarma.org/forums/index...phire-basket-case-resto-project.662523/page-4

In the second pic you can see what looks like a ball bearing in what appears to me to be a bronze sleeve bearing. I had mine upside down and I thought that was a ball bearing, but I gently turned the motor over and it didn't fall out. I also used a little telescoping magnet to try and lift the bearing out and that didn't work either. So, I believe that is actually the bottom of the shaft. Then I put a few drops of oil on the ball end and spun the shaft by hand, let it sit, then spun it some more, repeat, and let it sit for about 15 minutes or so before putting the thrust bearing back in and adjusting. This is how I remember it. It was a while ago. Oh, and I also put a dab of Teflon grease on the thrust pad too figuring it could'nt hurt.
 
marknoir said:
Hi. There’s no need to change the pulley. This is an intermediate step. If the motor is the culprit, then the Eclipse motor/controller will fix this issue. For now I will try to wire this one instead of mine.
Click to expand...

Ah so you are going to put the Eclipse motor controller package in? I have one on the Cosmos Eclipse I have, and it works very well. Will you have to disconnect the standard on/off controls and bypass all the internal motor regulation circuitry? If the internal electronics are fine wouldn't it be more cost effective to just transfer a pulley? Provided it can be done safely of course. But I suspect you get improved speed regulation with the Eclipse package, it is top shelf hardware.
 
Mister Pig said:
Ah so you are going to put the Eclipse motor controller package in? I have one on the Cosmos Eclipse I have, and it works very well. Will you have to disconnect the standard on/off controls and bypass all the internal motor regulation circuitry? If the internal electronics are fine wouldn't it be more cost effective to just transfer a pulley? Provided it can be done safely of course. But I suspect you get improved speed regulation with the Eclipse package, it is top shelf hardware.
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Eventually, when I win the Lotto ))). So far the highest I was offered for the table was $550
 
Mister Pig said:
So how is it going to be configured so you can install it? Can it permanently be installed the way it is?
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Yes. I can install it with a current set-up, with motor on subchassis, and I can install it in plinth, like yours. But it’s more work, and to me would offer no benefits.
 
marknoir said:
Yes. I can install it with a current set-up, with motor on subchassis, and I can install it in plinth, like yours. But it’s more work, and to me would offer no benefits.
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I was wondering more about the spindle pulley size and how the on board electronics would control it.
 
These Papst motors are self-controlled. All they need is 24v dc. Pulley size is compensated by slower speed of this replacement motor.
 
marknoir said:
These Papst motors are self-controlled. All they need is 24v dc. Pulley size is compensated by slower speed of this replacement motor.
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Great news, so you should be able to retrofit it and you will be up and playing. So a happy ending is possible.
 
Mister Pig said:
Great news, so you should be able to retrofit it and you will be up and playing. So a happy ending is possible.
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Not so fast. I guess this was a temporary thing, just like before with the light oil. W/f is back to audible 0.2%. Was offered $650 for it. Thinking about it.
 
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