New Technics SP10 motor controller specification

[sek]

It's the coil and circuitry in the lower right hand corner of Steerpike's drawing.

This is how it is drawn by Matsushita for the 1210Mk2 (from an early revision of the service manual):

[Steerpike]

>using the PLL to generate the lead / lag signal.

Oh yes, PLL control as well!
A PLL's lock range is quite limited and it is necessary to use velocity (RPM) detection to bring the PLL into lock range first, THEN do phase locking.

That AN5675 Ic used by the 1210 is pretty much a clone of the discrete circuitry used in the Sp10.

The major difference that I'm proposing is to vary the exciter oscillator signal, rather than try to adjust or vary the 3 phase coil signals. This means only one VCA instead of 3, and no need to control the symmetry / balance of 3 independant amplifiers.

The phase comparator method I have not decided on. Method-1 would be to use a ramp generator and sample-hold (as done in the original SP10).
Method-2 would be a digital method, using a phase-to-PWM converter (quite simple with one RS-latch and a D-flip-flop).
I guess I'll make one of each and see what works.

Theres also going to be a problem measuring the overall performance - the sorts of wow/flutter figures quoted by the best TT manufacturers are very low, and measuring a consistent improvement might be tricky.

I'm still interested to know what peoples problems are with the original SP10 electronics - WHY do you want to replace them?

[rich121]

I think one of the main reasons for an updated power supply/controller is aging/dated electronics..

Also, if you could isolate the motor from the controller, it would make it much easier to mount in a custom plinth, and I'm sure would add to it's sonic potential

Speed control ( .1% increments) would also be very nice..

Here are some of the very first posts of this thread that state what is wanted...


Shaun

Post #2
Yikes!! No takers?

OK, let's start:

1. Start/stop button (single or separate?)
2. Variable speed dial/slider (variable by what %age?)
3. Four user-presetable speed buttons
4. Reverse function (could be dangerous!)
5. Electronic Brake for stop function
6. Hold/ free platter when stopped.

Questions:

Should the controller (or a version of the controller) use the existing on-board controls or be self-contained?
Should it use own power supply or the existing unit?


__________________
Shaun Onverwacht
_____________


Post #3
Hello Shaun,

Have you started on this project? I know that if you take this to other forums (vinyl asylum for example) you would get much more attention.
I for one would love to be able to have "

1.) a modern power supply

2.) speed control (at least within 0.1% increments, and with knob not slider)

3.) Remote control

4.) Would also like some sort of "umbelical cord" made so that the tables' electronics can be isolated from the plinth, giving it even better performace.

I have 2 SP-10 MKII's both mounted on the factory Obsidian plinths...

Keep in touch!

Rick

[Shaun]

Hi Rick

Keep watching this thread. Steerpike is actually leading the development at this stage. He does appear to be much more involved than I have been. His view is to use the same design approach as originally used in the SP10, which is different from what I had originally intended, but significantly less risky (in terms of probability of success), as I have limited experience with microcontrollers.

Steerpike, can we agree on a work share, so that I can stop feeling so delinquent?!!

[rich121]

I will be watching for all posts..

Rick

[Steerpike]

My current holdback is that I have to go off & buy some power transistors (I like a big shopping list before I drive all the way across town to the supplier). I though I had them, but they are a mixed assortment of rare/oddball types. I figured I should do all developments with freely available parts. (TIP41 & TIP42 my current favourite 'use everywhere' medium power tr)

Another 'essential' for me is IR remote control - if you are going to do speed/pitch trimming, surely you want to do it from your listening position.

[rich121]

Take your time..
I wish there was some way I could contribute?

Rick

[Shaun]

Anyone read Japanese? The translated version also does not help too much.

SP10 works

SP10 works (2)

[Steerpike]

Happily the circuit schematics are understandable.

I've been toying with using PWM - probably around 5khz, instead of a more 'analogue' variable transconductance amplifier.
Still no power transistors!

In the meantime, a question: I have 3 platters from various sony direct drive machines (models unknown, I just got the platters). They are die-cast alloy with 4 strobe lines. (They have the autoreturn gear molded into the centre, and the magnetic stripe on the inner rim.)
Problem is, pretty as they are, they are very light.
Any suggestions on increasing their mass without grossly unbalancing them? I'm wondering if pouring polyester resin or similar into them will work or if it will never distibute evenly. They are too big for my lathe, so I can't machine them afterwards.

[Shaun]

If you can mill out the parts that make it not symmetrical, you stand a chance of maintaining the balance when filling resin. However, I have my Technics SP10 platter and two Lenco platters that have been balanced (evidently by drilling)- and these don't give any visual clue that were unbalanced to start with.