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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

Showing 9 responses by dover

dover
2,188 posts
 
Lewm,
"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. Everything gets even smoother than it was."
But you questioned whether I could hear the error correction on the DD's, even on the "inventor" of these SP10mkIII mods system whose TT I have heard and am underwhelmed.
Halcro,
You need to denude yourself and go and sit on a crowded beach. Open your mind up. It seems clear to me that the gist of the suggestion was the amount of error correction could be reduced by providing a more stable mount for the stators or whatever. If you hear a difference from the removal of extraneous bits, as you proclaim, then why could there not be an improvement from altering the structure or support of those extraneous pieces and other essential components. Your use of referential authority in dismissing Lewms suggestions is not a persuasive argument. I sincerely hope that if you have had design input into bridges in Oz that you have considered the ground upon which they sit. I do have some dear friends over there.
Yo
dover
2,188 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.

dover
2,188 posts
 
Lewm,
Not offended at all. I have learnt a lot from the various verbal jousts. I'm a great believer in learning what not to do is equally as valuable if not more so in learning what to do.
I dont dislike the SP10mk3, for me the jury is out until I can hear one in my own system. Its on my to do list.
The SP10mk3 upon which Alberts latest mods are based, last I heard it, is mounted in an acrylic/lead/acrylic sandwhich, runs an ET2 heavily modified with custom acrylic manifold & other tweaks, and Shelter 901. The main issue for me are the speakers, Acoustat 2+2 heavily modded in a room that is barely 10ft square. The system in question for me lacks timing, cohesion and transparency but as you know this is a sum of the parts and I would not necessarily ascribe this to the TT.
Albert in an earlier post alluded to power supply mods, and not including the bearing mods, hence the confusion. I cant give you any more insight, but in terms of product improvement in general, you just keep working on the weakest points. It would appear that the latest mods as you mentioned above are more around stiffening up main chassis and mounts.
It would seem to me that reviewing the Kaneta and Cotter mods are quite thought provoking. Looking at the cross section Halcro provided a link to indicates that perhaps opportunites exist to not only stiffen up internal mounts, but decouple or eliminate as much as possible from the main bearing and motor.
dover
2,188 posts
 
Lewm et al,
If you look underneath your Kenwood L07D you will find the archilles heal of the Technics SP10mk3.
dover
2,188 posts
 
The Technics SP10mk3, Victor TT-101, Denon DP80 are all what I would call upside down turntables. That is they are designed to drop into plinths and the motor/mainbearing assembly hangs like dogs balls below the plinth - waving in the wind. The connection points to the "plinth" are on a flimsy exoskeleton/cover into which the motor/bearing are screwed.
The resultant structure lacks rigidity and the path for energy dissipation from platter to ground is compromised. Its a labyrinth from the platter to the ground, and the unstable reference of the tonearm to platter is counterproductive in measuring the groove accurately.
Compare this to the Kenwood L07D, where there is a massive cast foot underneath onto which BOTH the motor/bearing AND armpod are BOLTED.
see
http://www.l-07d.com/plinth.htm
This is a far superior construction in my view in maintaining rigidity between the arm/platter and the platter/turntable/arm/cartridge loop.
If you check out the Exclusive P3 this also has a motor/bearing/arm mounting system with a superior motor/bearing/arm platform that correctly references the arm to the bearing/platter. see
http://audio-database.com/PIONEER-EXCLUSIVE/player/p3a-e.html

The Denon's use a decoupled platter arrangement to keep motor energy way from the cartridge, but they do not address the lack of rigidity from the upside down design.

In my view any serious attempt to replinth theSP10mk3 would include throwing away the exoskeleton and motor covers and bolt the motor, bearing & tonearm mounting base rigidly to a common subchassis to maximise rigidity and minimise any potential movement within the platter/turntable/arm/cartridge loop.
I'm sure dropping the SP10mk3 into a slate or panzerholz "plinth" makes a difference but it is only a half pie solution in my view.
dover
2,188 posts
 
Lbelchev -
Why do you think the Technics engineers were able to make the best turntable, but they were not able to design a suitable plinth?
I think the answer to your question is probably explained by the end use of the product. The Technics was primarily going into radio studios - hence the drop into a top plate/plinth makes sense. Conversely the Kenwood L07D and Exclusive P3 were primarily intended for domestic use, they did not have to consider dropping their TT into a DJ or studio worktop.
dover
2,188 posts
 
Hi Albert -
I refer to panzerholz or slate plinths in general - not yours.
I have no idea what your plinth or the Artisan Fidelity does. That you have addressed many of the structural issues within the Technics as opposed to just "cutting a hole" underpins the thrust of my post to highlight that to replinth is not a straightforward task - one has to understand the pros and cons of their TT design from top to bottom, inside and out, before they start planning a major upgrade such as replinthing.
The purpose of the post was to get people to look deeper and think more deeply about their TT in order to improve it. Much of the work required is documented on the net.
In Lewms' case he has to make a long term decision whether to keep his NOS SP10 relatively stock, or gut it, but if you are going to gut it, why go half way.
dover
2,188 posts
 
Kudos to Albert and others for generously sharing their knowledge with us.
Albert is on the money with product improvement. I think in the 70's cost was no object , but since then knowledge shared ( internet ), new materials and the lower cost and portability ( no pun intended ) of CNC machines means that the opportunity is ripe for re-engineering improvements at relatively modest costs.
Conversely we are in the age of mediocrity, convenience & cost cuts and some things are worse and were better built back then. Many materials due to shortages of trace elements and health & safety police have declined in quality.
dover
2,188 posts
 
Yes
Not really
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