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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
pryso
1,933 posts
 
Yes Lew, I realized and wondered about the same point after posting this time.

So not to put words in Technics' mouth, perhaps they were referring to the 500 tone arms just as an example. That was wild enough without suggesting 2,500 arms could track simultaneously at 2 g. each without impacting speed performance!

But it clearly states a load torque up to 5 kg cm.

Again, I might be more concerned with bearing wear over time than speed stability. But I'm not an engineer.
sebastienl's avatar
sebastienl OP
84 posts
 
Sonofjim and Lewm,

There is one way to adjust your SP-10 mkII speed, it is with an adjustable capacitor inside the turntable. My audio technician show me where it is and he has adjusted the speed to be spot on. Plus, yes, there is also the quartz that can be also adjusted and reseted.

Sébastien
sebastienl's avatar
sebastienl OP
84 posts
 
Back on track with the mat. I'm wondering which were the original turntables designed to used the 4 pounds Micro-Seiki CU-180 mat. If we have those informations, we can have another kind of feed-back by comparing their specs lists. Anyone know about those turntables?

Sébastien
lewm
13,110 posts
 
Dear Sebastien, See above the interchange between me and Tim (Pryso). For sure, the MkII was designed around its stock platter and mat. The OEM rubber mat weighs, as I recall a bit less than one pound. (I weighed mine on a kitchen scale, but I can't recall the exact result.) So of course the whole was not designed for a 4-lb mat. However, it is clear that because of the torque-y motor, there is some "headroom" to use a heavier mat. The question is "how heavy"? That is to be determined by the end-user, I guess. I am a bit more conservative than many others and so would not consider going much above 2 lbs. But I think we can agree at least that 4 lbs. is about at the outer edge of the envelope. Lots of people report good results with the MS mat and with TT Weights mats that also weigh 4 lbs, so I am not about to say that it can't work well. Like Tim said, at some point, in addition to speed stability, one also has to consider the wear on the turntable bearing of using a much heavier than OEM mat. FWIW, I used an SAEC SS300 mat on my Mk2, which by coincidence weighs not much more than the OEM mat and sounds a heck of a lot better. Same goes for the Boston Audio Mat2, which I now use on my Mk3.
sebastienl's avatar
sebastienl OP
84 posts
 
Hi Lewm,

I think that I haven't express myself correctly. I was meaning that by comparing the specs of the turntables that were designed to used the Micro-Seiki CU-180, there are some chances to see turntables with specs similar to the SP-10 mkII.

Anyway, I respect both parties in this discussion and I hesitated a while between Boston Audio mat and Micro-Seiki CU-180 mat. Inspired by certain critics, I finally commited myself and just bought a CU-180 new in box at a good price.
This said, I'm still interested to try one day the Boston Audio mat.

Sébastien
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