[Russtafarian]

I was figuring out the logistics of all the mods when it occurred to me, there might not be a need to bolt the plinth on the subchassis.  If I install a spike where the spring seats were I could have the subchassis stand on its own and the motor/plinth separated from the rest.  Sort of like having a motor separate from the table.

Interesting approach.  Keep me posted on how this works.

Russ

[Grbluen]

Neo,
Good to hear that you're feeling better and making progress on your mods. Keep at it and keep us updated!

Grb

[neobop]

I'm now trying to figure out how to add some weight to the plinth to stabilize it.  Without the chassis hanging from the springs it's a little light.  I'll look around for some sheet lead like the stuff on the chassis, but it seems like it's not used much anymore.  Space is a problem so lead seems like the ideal solution.  BTW, lead is great stuff when combined with other build materials.  Its density slows down vibrations and has been used for a long time to improve the performance of tables and speaker cabinets. 

I like the idea of isolating the motor and it doesn't affect the relationship between arm and platter.  I have a good feeling about this.  I'm reluctant to say more, I might jinx it.  Suffice it to say I haven't used this table for around 25 years, except for a brief period after I got married. 
neo

[neobop]

It turns out you can buy lead on Amazon and probably fleabey.  The price is high and the shipping is ridiculous.  A 1' square piece 1/16" thick is $17 + $11 shipping.  It turns out that a roofing supply might have it.  They call it flashing.  I got a 3' x 3' piece for $60.  9 sq feet is a lot of lead, enough for a fleet of tables.

Lead is easy to work with.  You can cut it with a tin snip.  Gloves are recommended.  I used contact cement to attach it.







The lead seemed to help.  The plinth was a little more stable.  My impression is, this is the best I've ever heard this table, and that's with the rubber belt.





I'll have to check it out further and report back.  I don't think the video tape will fit on the pulley.  The rubber belt is as wide as a cassette tape.  There are other options for modifying the table. 
I think defeating the suspension is the way to go.   Stay tuned to this channel for more of the Sota Saga.
neo 

[Grbluen]

Neo,
Great to hear that you're happy with the mods! Everyone should be so lucky to have a Sota as a backup.
Congrats,
Don grb

[neobop]

Thanks Don,
I always liked the look of this table and the platter is excellent.  I didn't use it because of speed stability and suspension issues.  I formerly had an LP12 and I was a set-up tech for that table.  With careful tuning the Linn can be made to bounce perfectly.  It makes a big difference.  Any lateral movement of the suspension is a disaster with a motor not attached to the subchassis.  Even if the motor is on the subchassis, lateral movement interferes with tracking.  As I mentioned before, having a fixed motor not on the subchassis, combined with vertical movement of the platter, will cause the belt to shimmy or  stretch and shrink back.

I'm not positive yet about the speed issue.  It seems much better, but not quite up to quartz locked standards.  All I did with the electronics is clean the speed pots.  I'm going to try cassette or 1/4" tape.  If successful, maybe I can cut the video tape in half lengthwise.  Think I'll get one of those laser tachometers.

It's been fun getting this together, but I'm not done.  Some of the things I'm thinking about depend on the drive belt and if I need a moveable motor.  There's the possibility of a new armboard and arm support system.  A steel plate under the subchassis seems like a good idea.....
neo   

[neobop]

Thanks.  I've had the table completely torn apart to to figure out what to do with the stretched out springs.  The springs in the front hang so low the bottom plate hits the rubber footers.  I tried rotating them, front springs back, back springs front, but that wasn't enough.

If I can find a way to fix the suspension without a big hassle or expense, I'll take another run at resurrecting the Sota.  For now I got it rolling with a cheap cartridge and beat-up MMT arm and gave it to a friend so he can listen to his garage sale vinyl.

Russ

Russ,
I still have the rubber belt on, and I think it's better without the suspension.  My set-up and disassembly is a bit of a hassle, but you could just bolt it together like I was going to in the first place.  BTW, those big washers on the bottom of the subchassis are called fender washers.  The OD is 1 1/2" and the ID is 1/4" (in this case with a bigger size).

If you don't want to drill through the top plate, you could hang corner braces from the sides and leave a space so you could adjust the height.  Other than that the only other option I can think of is to use the bolts for the feet to bolt it together and put spikes on the chassis.  The only problem with this is those bolts are too long. So you'd have to figure it out.  The mount for those bolts (feet) is kind of flimsy, but seem to be okay under load.

When I set-up now, first I have to mount the chassis and platter and get it level.  Then remove the platter.  Take the rubber feet off and put the plinth in place through the holes in the chassis.  Then put on the rubber feet and rough in the height.  Then put the platter on and set the height so the pulley is in proper position.  Insert arm and armboard.
When I take it apart I remove the arm and then the platter has to come off before the plinth because the motor board prevents the plinth from going first.  That's a PIA, but once set-up it wouldn't have to be done often.
neo

[Grbluen]

Neo,
I found this and thought you might be interested.
I have no idea if the info is still relevant, but it may lead to a better
source for 1/4" tape.

 http://www.AudioAsylum.com/audio/vinyl/messages/58/588497.html

Grb

[neobop]

Thanks for the link Grb.  That's an interesting thread.  Doug Deacon talks about motor quality and drive belt type.  It's possible that tape drive might be too revealing for some motors.  I haven't started experimenting with that.  I'll let you know how it works out.
neo

[Grbluen]

Bump.

[neobop]

The table off to the side for now.  I'll have to take it apart and see what's going on.  That arm is an Alphason 100S; it has no azimuth adjustment and I noticed it's off.  Either the corner of the armboard support is on a nearby washer sticking up, or the subchassis is warped.  I fear it's the later as I checked the washer clearance before screwing in the support, but maybe it moved and I didn't notice.   

The subchassis is basically a 1/2" piece of MDF with some lead in the middle and those blocks at the corners.  It is 30 years old, but what were they thinking?
So, to do it right it needs a steel subchassis plus MDF or a better substitute like polyester resin mixed with ground stone or bentonite.  Maybe a layer of lead plus the blocks around the bearing support.  That should do it. 

While I'm at it I'll get rid of that silly armboard and support, or I could correct the armboard one way or the other on the same subchassis and sell it.  It looks like I'll have to bolt the whole thing together anyway, the plinth is too unstable.  Thread drive seems to be just as good or close enough and it can be installed on a fixed motor. 

Last week the furnace died and I didn't even think about it.  I'll probably rebuild almost the entire table.  You know what they say, if something's worth doing, it's worth doing right.  Famous last words.
neo     

[Grbluen]