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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
13,247 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.
sebastienl's avatar
sebastienl OP
84 posts
 
Hi Lewm,

Funny, I was just about to ask Dover what's his reference turntable.

Have a nice week-end,

Sébastien
lewm
13,247 posts
 
Sebastien, Perhaps we shall find out.
albertporter's avatar
Ag insider logo xs@2x
albertporter
4,949 posts
 
Lewm,

Regarding
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.

Nothing is done to the power supply beyond Bill's initial rebuild. My suppy remained here during this last upgrade, so no way anything was modified beyond the motor chassis.

Also, regarding Dover
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 viewed images of the MK3 that Richard owns and if I had not been told it was once a Technics I would not have recognized it. I have no idea if what was done makes it better or worse than original or how that fits with the mechanical mods he came up with.

Richard told me he was using Acoustat 2+2 speakers and all his electronics were built by him. Further separation from mainline components that one might use to judge total system performance.

For those reasons I'm not sure I could tell anything about the MK3 or any other table that might be put in play. Not saying there is anything wrong with what was done, more like listening to a system at a show where nothing is familiar and trying to offer an accurate assessment.
lewm
13,247 posts
 
Thanks, Albert. I thought I had been told that there were some mods to the outboard PS associated with your upgrades. I was obviously misinformed, or my memory is playing tricks. Is "Richard" the guy who invented or first devised the beneficial modification(s)? Even Dover admits in the quoted paragraph that he is unable to make a judgement regarding the modified MK3, because so much else about the system is in constant flux.
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