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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 Sonofjim,

I was considering the Micro-Seiki CU-180 seriously and someone just offered me one today at a fair price.

Could you explain me more about the "better weight for the mkII" when you compare the Boston mat to the Micro-Seiki? I have read many comments regarding the good match between the Micro-Seiki CU-180 and the SP-10 mkII. The latest seems to have enough torque for the heavy Micro-Seiki copper mat.

Well, I'll be glad to know your opinion on that subject.

Sébastien
sarcher30
596 posts
 
IMO the cu-180 is way better than the Boston Audio mat1 in my system. The Boston mat is good but the cu-180 blocks EMI coming from the motor. Also IMO it is not too heavy for the SP-10 mk2. In fact the extra weight may be a benefit. I think it smooths out the speed a little. The cu-180 definitely lowers the noise floor compared to the Boston mat.

Sonofjim, Have you tried the cu-180 in your system? If you had I would be surprised if you did not like it.
lewm
13,268 posts
 
If EMI is a real problem, one could also make a shield expressly to treat that problem; the shield can be placed under one's mat of choice. I did exactly that for my Kenwood L07D, which uses a stainless steel platter mat, which you would think is by itself a decent shield. Nevertheless the L07D sound was improved by using TI Shield (a Texas Instruments product). I bought one square foot and cut it in the shape of an LP so it fits under the SS mat. Works very well.

What is the weight of the cu180? This is an old and pointless debate, but using a much heavier than stock platter mat in theory is not a good thing for a servo-controlled direct-drive, where the system was designed to cope with a certain inertial mass. Note, I say "in theory". I realize there are practical exceptions. And actually I think the cu180 is within shouting distance of the weight of the standard mat, about the same as the SAEC SS300, which I know does no harm on the Mk2. Not as crazy as some of those very much heavier TT Weights mats.
sarcher30
596 posts
 
Lewm, The cu-180 is 4 lbs. I had the same concerns about too much weight affecting the servo in a negative way. In practice this is simply not the case. If anything it's affecting it in a positive way.

I had some TI Sheild that I put under my Boston mat. TI Sheild is very springy stuff. If it's not perfectly flat it will not lie flat unless you have a heavy enough weight on top. The Boston mat is not heavy enough. A heavier mat negates any weight saving advantage. It is conceivable someone could get it flat enough to work but it's very difficult. I ruined the TI Sheild I had messing with it. I could get some more and try it under my cu-180 and see if there is any improvement.

Will your stainless steel mat from your Kenwood fit on your SP-10 mk3? That would be an interesting experiment. I believe Albert Porter is using a SS mat on his mk3.
sebastienl's avatar
sebastienl OP
84 posts
 
As I said above, I am considering the Micro-Seiki CU-180 mat from a seller who's serious and from whom I already bought. The seller tell me that the mat is brand new and was made in 2011. I'm a little bit surprised because I was sure that Micro-Seiki was not in the business anymore and this mat not in production for already few years. Is there some of you that can confirm the time that the production of the CU-180 ended?

Thanks,

Sébastien
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