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
I was thinking to move this thread to the "Tech talk" section. Is this a good idea? If so, please feel free to do it.

Thanks,

Sébastien
You really do need to take this to a more tech-oriented site. But one comment I have is that there are a large number of electrolytic capacitors on board the main chassis, and they are not exempt from failure or faulty operation. If the caps on the main chassis board are still the OEM ones, I recommend replacing them empirically. Then maybe start over with these measurements.

Also, if you have a connection with Bill Thalmann, he can probably help your guy over the phone, if indeed the problem persists once all the remaining lytics are replaced. I am not at all surprised that neither OMA nor Artisan could help; those guys are not techies.
Regarding the comment from Lewm-

"I am not at all surprised that neither OMA nor Artisan could help; those guys are not techies."

OMA does not provide free technical advice. We employ several technicians. They do not work for free. I explained that to the OP.

Considering that OMA has created a completely original, ground up motor control for our Tourmaline turntable that uses the SP10 motor, and that does not use PLL or DC, your comments are laughable.

Jonathan Weiss
OMA
Then you are free to laugh. First you say that you do not provide free technical advice, and then you brag about your technical expertise, which you will not provide to the OP, because you "employ several technicians" who "do not work for free". So in the final analysis, and as regards the chances for the OP to get some help from you or your company, where was my error? The OP states that he contacted you and that you could not help (his words). I take his statement at face value. So why are you laughing?
For a government research scientist, Richard, you don't seem to understand much.

My company employs technicians- in other words we pay them. They do not work for free. We do not provide free assistance to other technicians who cannot figure out a problem.

Guess you did not understand the part about OMA creating a completely new motor control for the SP10, either. But then again, we're not "techies."

Too funny.

Jonathan Weiss
OMA