Hi all. So I got myself another project. It’s a Sota Cosmos Mk IV. Good condition, so I couldn’t pass it by. This version utilized an AC motor, and I’m totally unfamiliar with it. My previous Cosmos was one of the very first ones and had a DC motor. I ended up replacing all in that unit as per Mr. Pyramid’s instructions. Before I do the same to this one, I wanted to see if the factory set-up can be restored. Anybody familiar with Sota AC motor set-up? Thanks in advance.
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Hello Ralph! Thank you. This looks to me like a hard-drive motor… I don’t know if these pictures will help, but here they are. The w/f are not great at all, but they went down to acceptable levels after I put some light oil on shaft/bronze bushings. Familiar situation: oil will leak out in a couple of weeks, and w/f will come back. This is something that I think only Sota can fix.
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Thank you Pyramid! That’s what I thought. I might change the electrolytics throughout just in case, but it seems that every older Sota I come across has problems with bearing. After a long struggle (very difficult to remove in this vintage)I finally removed the platter. Cleaned everything, put new grease on the ball but on purpose left shaft and bronze bushes dry, as they were. W/f were the same. Then I removed the platter again and applied a few drops of light oil to shaft and bushes. W/f immediately went down to very acceptable 0.07% rms. Of course this will only last a few days, until oil leaks out from the bottom. For the life of me I don’t know solution to this, unless Sota can fix it with their tricks. I still have the same problem with my early cosmos with AA motor and your controller.
Is it not possible to seal the bottom of the platter bearing housing? I don't have a picture of the part but after degreasing it should be possible to apply a suitable sealant to eliminate further leakage.
No. The design is such that no sealing is possible. I thought about it, I was very impressed with Mitchell and Audio meca oil bath with spiral supply channel, but it’s impossible to implement here because of the vacuum channel design…
