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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
sebastienl's avatar
sebastienl OP
84 posts
 
Hi Lewm,

Regarding the modifications discussed above:

"Albert is ecstatic about the new modifications, but he really did not know much about what was done. I then talked to Bill about it. Mostly it is about dampening vibrations and firming up the stator supports. Bill notes that as the servo system corrects for speed errors, some of the energy of the motor is used up in micro movements of the stators, predicted by Newton's Third Law (For every action, etc...) (Ideally, all motor energy would go into moving the rotor/platter.) These tiny wiggles of the stator then in turn produce a tiny correction error sensed by the servo, which senses the fact that some of the torque went into moving the stators instead of the platter. This begets another correction from the servo. And so on. With the modification to the stator mounts, there is less energy dissipated in moving the stators, more precise speed correction by the servo, and far fewer events that trigger the servo...."

Do you know if you can do them on the SP-10 mkII?

Sébastien
lewm
13,110 posts
 
Bill can do it for the Mk2 as well. In fact, for some reason the cost is much less vs the Mk3. Ask Bill.
sebastienl's avatar
sebastienl OP
84 posts
 
Ok, thanks Lewm.
dover
2,247 posts
 
Lewm,
I've known the inventor of the mods for 25+ years and have followed the development of his system. Unfortunately there are many issues with his system outside of the turntable with which I have issues so I have to judge that particular SP10mk3 in that context. As the TT is in constant development I may or may not have heard his latest mods.
I also have other personal friends who number between them another 2 SP10mk3's and 3 Kenwood LO7D's in various states of mods for reference.
I have heard the Denon DP100M back to back with my own Final Audio, but unfortunately it included the integral Denon arm and the sound was not good, I suspect due mainly to the arm.
Back to the SP10mk3, I am not writing it off, due to the constraints under which I have heard it, but have not yet heard anything on 3 samples that leave me with a feeling that I must have it. With regard to the SP10mk2 I have no interest as it is so far off the pace of the mk3 and even the L07D that any time invested would be wasted time in my view. I would estimate that I've heard about 10-12 SP10mk2's over the years.
I should add that when I say I've heard a product, that means I've listened at length in a system I know reasonably well and feel qualified to comment.

lewm
13,110 posts
 
Dear Dover,
I hope you did not think I was attacking you for not liking the Mk3. Of course, you are entitled to your opinion. Nor would I care to make the effort to change your mind. But I am interested in what you know about the Mk3 mods that were done by Bill to Albert's Mk3. Can you describe them in any detail? For one thing, I am curious about what is done to the power supply module. For another, I wonder whether the inventor is supplying some actual parts to Bill, for him to effect the modifications. Also, where do you live? Seems you are somewhere outside the US at times, other times not.

Just for my own curiosity, can you say what turntable(s) you do like and also describe the remainder of your system? My system is posted here. Thanks for your input.
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