Good for you. I know people with working Sotas and they don't complain about speed instability. If you read the very first review of the Cosmos in 1989, speed instability was noted right away. A few months later Sota sent another unit with some changes, and speed stability was greatly improved. I guess my unit was of the first generation. I also love it's SQ, but I don't care anymore to put a $1500 into it hoping that it solves this problem.
hi
Jusr looked over your restoration again. Lots of useful info there.
I found that in my bearing any normally viscous oil on shaft causes audible wow. Yesterday I cleaned out the bearing again. Used small dab of ptfe Superlube on top again, but this time just a litle bit of bike chain oil, CarbonPro Dry. It’s a liquid as water. I don’t know if it will stay on the shaft. But the w/f figures went down to 0.15% again. I don’t know if they will stay there, or go up again in a day or so. I also don’t know if it’s normal for this bearing to not accept heavier oil. Perhaps replacing bushings will cure this problem...
Soooo... I was pursuaded by some good faulks here and elsewhere not to throw this thing out, stop my defitust attitude and give it another wirl (pun intended).
So I cleaned out all of the oil out of the bearing again; put a small dab the usual ptfe Superlube grease on top; but this time I used super-light bike chain CarbonPro lubricant on shaft. It’s a liquid as WD-40. And this may prove to be a problem, because WD-40 does not last. I think this one may evaporate soon. But for now, for the third day, wow/flutter figures are 0.15%, which is very low for this generation of Sota. Another thing I want to try is graphite lubricant. If I’m able to keep w/f figures this low, then I will keep this table.
So I cleaned out all of the oil out of the bearing again; put a small dab the usual ptfe Superlube grease on top; but this time I used super-light bike chain CarbonPro lubricant on shaft. It’s a liquid as WD-40. And this may prove to be a problem, because WD-40 does not last. I think this one may evaporate soon. But for now, for the third day, wow/flutter figures are 0.15%, which is very low for this generation of Sota. Another thing I want to try is graphite lubricant. If I’m able to keep w/f figures this low, then I will keep this table.
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Have you ordered that OEM belt yet?
Audiofreak71
Audiofreak71
dogwan
Dogwan
This is the reading I got on my early SOTA Sapphire Star today using "RPM Speed Analyzer" app for Android.
This was from a cold start, I didn't dial in the speed beforehand, and I just recently re-lubed the spindle with Phil's Tenacious Oil. Belt is OEM ordered directly from SOTA circa 2015.
This was from a cold start, I didn't dial in the speed beforehand, and I just recently re-lubed the spindle with Phil's Tenacious Oil. Belt is OEM ordered directly from SOTA circa 2015.
Hi
Out of stock. The lowest readings I get are with the aftermarket chinese belt. It’s diameter is larger and it puts less pressure on motor. So motor can be the culprit after all. But it gets to speed really fast. Mystery...
These are great figures! I wish mine was like that. I have the same app I think, but it looks different. My lowest figure I got today was .21%, which sucks. That’s the very top test in photo.
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Morning. 8 am. W/f 0.14%. Strange. Figures are low in the morning, and go high at night. I measured my wall AC, AC after filter, DC from PS/vacuum unit, DC going to the motor - everything is the same. I will let it spin for a couple of hrs and measure again. Btw, I will say this again, the lowest figures are with the chinese belt, because it’s diameter is larger and it puts less pressure on motor shaft. So it seems that the main culprit is the motor after all. Perhaps when it warms-up, it’s internal system goes out of wack. Next I will remove all the lube from the shaft completely and run it dry as some suggested, relying only on the bushings. When they are new, they are self-lubricating. I think that they get old they lose their lubrications properties. I think this is the main reason to change them, not the wear. ButI don’t think this will make a lot of difference, since Dogwan’s table exhibits very low w/f figures with heavy oil. I wish I could locate a regular Sapphire motor/controller board unit and try it. There’s one for sale locally but the guy wants $270 for it.
dogwan
Dogwan
Not sure if this will be helpful, but when I got my Sapphire it was a literal basket case and missing the PS. Here's the thread on my rebuild (on a budget)....
https://audiokarma.org/forums/index.php?threads/sota-sapphire-basket-case-resto-project.662523/
I ended up using an HP 0950-4340 printer power supply which you can still get at Amazon and Ebay for a few bucks. Still using it and it has been rock solid with the Pabst GS 38.09 motor.
I still don't have my vacuum section running. Someday I will order up a little 12v vacuum pump and figure out a circuit to run it.
If you read through my thread you'll also see how I removed the vacuum platter and re-glued it. For now I am using a 3 or 4 mm thick wool felt mat to lift my records above the vacuum lip.
https://audiokarma.org/forums/index.php?threads/sota-sapphire-basket-case-resto-project.662523/
I ended up using an HP 0950-4340 printer power supply which you can still get at Amazon and Ebay for a few bucks. Still using it and it has been rock solid with the Pabst GS 38.09 motor.
I still don't have my vacuum section running. Someday I will order up a little 12v vacuum pump and figure out a circuit to run it.
If you read through my thread you'll also see how I removed the vacuum platter and re-glued it. For now I am using a 3 or 4 mm thick wool felt mat to lift my records above the vacuum lip.
Hi. I read your thread very carefully )))
I’m having problems with speed stability, and so far I can’t pin-point the problem. I wish I had a spare motor to try. My power supply puts out solid 39.5 v dc; motor control regulator board is different from your, Cosmos uses a 317 regulator on a separate board, and native regulators on motor board are disabled.
If you need help with vacuum, I can help, since I have rebuilt mine and now it’s “sucking” like new. You can call me I can send you my phone in PM.
I’m having problems with speed stability, and so far I can’t pin-point the problem. I wish I had a spare motor to try. My power supply puts out solid 39.5 v dc; motor control regulator board is different from your, Cosmos uses a 317 regulator on a separate board, and native regulators on motor board are disabled.
If you need help with vacuum, I can help, since I have rebuilt mine and now it’s “sucking” like new. You can call me I can send you my phone in PM.
MisterDK
Addicted Member
The SOTA tables I have and have seen, use “oilite” type, sintered bronze bushings which are oil impregnated. I believe the oil that comes in them is -around- the same as a 20-30 weight automotive engine oil. You basically just want to clean them off and soak them in a similar oil, remove any excess and then reassemble. Use just enough grease on the sapphire/bearing to hold the ball in place. I think that any heavier weight or stickier oil shouldn’t be on oilite bushings.
Thank you
This is true. Question is - how do you “soak” then? If I feel the bearing opening where the bushings are with oil, it will leak out through the vacuum channels, and will completely clog them. After 32 years I think these oil bushings no longer hold any oil. I look at them and see the micro chambers open. When I got the table with that horrible wow, the bearing was lubricated with some yellowish oil that felt like auto oil.
MisterDK
Addicted Member
On my Star, I plugged the vac channels with broken off q-tips shafts or the ends of bamboo skewers; don’t remember. I first wiped clean, then sprayed out the whole spindle bearing with brakekleen solvent. After plugging the vacuum holes, I poured in synthetic motor oil and let sit overnight, drained it and then wiped out it with paper towels. I didn’t spray the brakekleen in for long; just a few blasts from the can. I was scolded by a well known SOTA guy for doing this, as the sapphire thrust is supposedly glued in place. Don’t soak it in a strong solvent.. Use a good quality, lightweight oil on the bushings/shaft but don’t use much when you reassemble. Worked for me.
MisterDK
Addicted Member
That one looks much more worn than mine did. Mine was only marked from use, not dimpled like that one. Those are available on ebay, btw - but contact the seller to be sure of size. They claim theirs is for “early Sapphire”.
I can’t even see the vacuum channels on mine... And I don’t know how to remove the old stone and put in the new one. This seems to be beyond my capabilities.
MisterDK
Addicted Member
If the steel shaft fits smoothly and doesn’t show much wear, then the bushing is probably OK too. If it’s a sloppy fit, then you’ll need a replacement bearing/platter assembly. As far as removing the old sapphire thrust; they should shatter by using a steel punch/drift and a hammer. You’d then need to carefully clean out all the tiny bits and any adhesive, before fitting a new thrust. If you don’t feel up to it, you’ll want to contact SOTA about getting a replacement assembly.