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Technics SP-10 mkII speed adjustment question

Hi,

I'm on my way to complete my Technics SP-10 mkII project. Actually, a friend of mine, a professionnal audio technician, is working to upgrade the PSU, which is done but a small adjustment on the speed must be done and he need some cue on this issue.

We already asked Bill Thalmann, Artisan Fidelity and Oswald Mill audio. Plus, I'll post on DIY Audio today. We'd like to get the answer as quickly as possible to finalized this for the week-end. Hope someone on Audiogon can help.

Here's the message from my technician:

"Hello,

I'm an electronic technician and I do repair for audio equipments, vintage, hifi pro and more. I have a client here that brought me his turntable Technics Sp-10 MKII to fixed. I have a little question about it and he gave me your email because he pretended that you have some experience with this kind of materiel. So, hope that you can response my technical question.

I replaced all capacitors in the power supply and a big solder job. I checked for defect solders or capacitors on the circuit boards inside the turntable and I tied to do the adjustments . Everything seem good right now, the turntable work fine. I tried do do the period adjustment with the VR101 and VR102 potentiometers like in the service manual ( see attachment, Period adjustment method). When I looked the stroboscope at the front of the turntable, It's pretty stable but I can see a tiny rumble at 33 1/2 and 78 speed. 45 is the more stable speed for the stroboscope. So, I fixed the phase reference with T1 at 18us of period and I try to do the period adjustment at the point test T and S on the board with the O point for reference. When I put my scope probe on the T point, I can observe the stroboscope running. It is not stable at all. If I pull off my probe, the stroboscope is stable again. So When I have the 2 probes at point S an T at the same time to do the adjustment, it's impossible to fixed the wave T because it going right to the left on my scope. When I turned the VR101, the T wave going faster or slower but never stable. I tried to ground lift my scope, plug it into the same power bar and try to pull off the reference at the O point. I can't have a setup that I can see a stable T wave in my scope with the one that I can do the right adjustment. Why? Is there a problem with the turntable or maybe it's a incorrect probe or ground setup? Please let me know what you think.

Best regards"

Thanks for help,

Sébastien
128x128sebastienl
lewm
13,418 posts
 
Tim, It goes to what we talked about in the plinth thread. IMO, you need some way to appose the tendency for the whole chassis to want to rotate in the opposite direction from the platter, again described in the statement of the Third Law of Motion. Here we have Albert hearing great improvement from firming up the stator supports and whatever else was done in that direction, even though his Mk3 was already firmly in the grip of his large and heavy hardwood plinth and damped already by his iron block/brass rod device that is in contact with the bearing housing so as to draw off energy. One can only imagine what potential is left untapped when on uses no plinth at all. (I hope none of those guys are reading this thread; I don't want to go there again.) To each his own.

Sebastien, Great to hear that you are in a good place. I was in Bill's shop last week and may have seen your Mk2 on his bench.
halcro's avatar
halcro
2,664 posts
 
Lew,
Of course some of us are reading this thread and some.....like me....would prefer you to stick to 'medical science' rather than structural science?
Whilst invoking the Laws of Newton may appear to add credence to your statements.......there must be some 'connectivity' to those same invoked laws?
Here is a cross-sectional view of the Technics SP10Mk3
HERE
which shows that.....like all platters........it is a cantilever supported only at the platter support around the spindle which then takes all the load to the bearing. If someone can demonstrate any other contacts points between the platter and the outer 'trim'......I'd be obliged?
Now if the spindle and it's bearing are of the minimal friction type desired by many designers........where precisely are any loads distributed to the 'whole chassis' as you claim?
lewm
13,418 posts
 
Henry, I should have known that, like the shark in "Jaws", you were lurking out there. I never should have gone swimming here. I could not care less about this issue; I have made my decision, and you have made yours. This does not make you or me a bad person. Moreover, I do not think the choice is a make or break one; I am sure your system sounds wonderful. Carry on. Now, will you release my foot so I can swim to shore? Thx.
sebastienl's avatar
sebastienl OP
84 posts
 
Hi Lewm,

It's impossible that you saw my mkII at Bill's place. Bill only helped by email my audio technician here in Montreal for the detail regarding a probe to take a mesure.

To give anybody an estimated of the job done and the cost, here it is:

-PSU upgrade (all capacitors with high end ones, new IEC plug, new led in front);
-Have done all in new silver solders;
-Checked all the capacitors values in the turntable;
-Adjust the speed;
-Lubricate it with original oil.

It costed me $150.

Sébastien
sonofjim
557 posts
 
Pryso,
My system pictures are so out of date that I've considered just taking them down. Both those tables are gone and have been replaced with a pair of Thalman redone MKllls. One is in Chris Thornton's large constrained layered plinth, the other is in the Dobbins plinth utilizing only the platter and motor unit. Both plinths are dual armed. I'm still in the process of setting all this up and may get around to posting better pictures at some point when finished. Tonearms are EPA 500 (6 different wands), an exotic German carbon fiber arm, SME 312s Magnesium and soon a 12" Reed 3P.
Lewm,
I wasn't aware of this mklll mod Bill is doing until now. Please post all you learn on this especially if you have it done.
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