Technics SP-10 mkII speed adjustment question


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:


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,

Sarcher, I agree. Carry on. There are many others who do the same as you, so obviously the net results cannot be so terrible, in fact must be good.
Well, I'm not going to commit myself for the purchase of the CU-180 mat for the moment. It looks like this seller, even with many positives feed-back regarding other items, have already sold two counterfeit CU-180 mat to Audiogon member. By the way, I still consider the Boston mat 1 or there's the option to look for another CU-180 at a good price.

Sebastien, Sarcher,
Yes I have tried the CU-180 with the mkll and did like the sound. I have two CU-180s and currently use each on custom MKlll tables. I thought the mkll sounded more dynamic and alive with the Boston mat ll, which BTW is an upgrade from the mat l, and the SAEC SS-300. The SAEC is actually closer in weight to the Mat ll than the CU-180 which does weigh 4 lbs(essentially what a TT weights mat weighs). Both the SAEC and Boston mats are closer to the original mat weight. I prefer the CU-180 on the mklll with it's considerably greater torque. The Boston is affordable and sounds great, no worry about counterfeiting.
The SAEC I believe was made with the MKlll in mind and is Steve Dobbins recommendation. Believe it or not, even though I have the SAEC I haven't yet gotten around to trying it on a MKlll as of yet.
Dear Sonofjim, I went from an SAEC SS300 to the Boston Audio Mat2 on my Mk3. Both are good, but I do slightly prefer the BA. Both are far superior to the factory rubber mat, for sure. I could envision that with certain tonearm/cartridges, the SAEC might be preferable to the Mat2. Don't know for sure.
Sonofjim, do you have more than one system set up? Your system photos show a VPI, but neither of your SP-10s.

I'm always looking for ideas/recommendations regarding the Technics.