Exact dimensions of the SL-1200MK platter anyone?

[djlithium]

Ok since I happen to work in VFX for film and TV, I figure I might as well put some of that to use in my own pursuit of building a viable mastering solution out of the SL-1200MKII turntable, of which I own 3 pairs. I might as well experiment a bit if I can.

So my first question is, does anyone here happen to have an EXACTLY perfect model of the SL-1200MKII turntable or the platter itself for scale in OBJ or LWO or even 3DS format or some other similar data set?
This will save me a bit of work, but its not totally required.
I don't have a proper set of measuring instruments here, but I think I can mock up the idea cleanly in 3D and then show it you guys.

My first goal is to build (in 3D) a platter that sits directly on top of the regular SL-1200MKII platter and rises above the tone arm assembly before spreading out with a lip (and that lip will be very thick btw) that will support a 14" master lacquer. This platter will be made out of acrylic or poly urethane and will have a center hole on the bottom so it sits directly on the center post of the existing platter, plus two "posts" that will sit into the platter holes on the SL-1200 platter, flush with the back of it. I may devise a "plate" that is also poly urethane or acrylic that will sandwich together the existing platter with the new top platter. This is to ensure its secured and doesn't wobble off. I may have to remove the protective "cage" that sits above the electronics assembly inside the deck itself for clearance but that's another matter.
The platter itself will be multi-level/material. The first layer at the bottom would be a thin rubber for dampening and then it will be acyrilic or polyurethane again until after it rises above the level of the SL-1200 platter center post by several mm. Then another layer of rubber, possibly neoprene before another thick (like 1 1/2") acrylic until its above the level of the tone arm assembly at 1mm set height plus some extra. This is where it will spread out to a full 14" mastering lacquer size and then be at least 1" thick before another small thin layer of rubber on top for the final layer and of course a center post. Optional screw in post for the offset post for use with masters, but this way it can also be used to cut PVC blanks, providing those don't have holes offset beside the center hole.

The idea being here is that the SL-1200MKII rumble can be reduced to a minimum if not eliminated and adapted for 14" master cutting.

Any thoughts?

Cheers.

Kel.

[opcode66]

The more weight you add to the platter the less likely that the direct drive motor will be able to turn it at startup. Or maintain speed. The motor in technics turntables is not very high torque. And, if you mod them for more torque via resistor swaps it becomes even less stable with respect to maintaining rotational speed.

I suppose what I'm trying to say is why not start fresh? If you are serius about designing a new lathe, especially for mastering, why base it on a consumer level deck?

If you'd be interested in collaborating pm me. I've been learning more cad such that i can start designing parts for fabrication. My approach has been to use as many off the ahelf parts as possible. All held together by custom rigging. All driven by chips programmed by me.

[markrob]

Hi,

I don't agree with Op's analysis, but I do agree with his conclusion.

Adding mass within reason to the 1200 will not reduce the speed of the platter due to torque limitations of the 1200 motor. All this will do is increase the time to reach speed. This is because:

Acceleration = Torque/Interia

If you add mass , the inertia is increased which decreses acceration. Once at speed the torque is no longer used to accerate the mass and can be applied to cutting. Adding mass also increases the load on the turntable bearings which does add increased drag, but the bearings on the 1200 are pretty good, so I would not expect this to be a major factor as long as the increase in mass is not crazy.

What is unknown is how the servo will react to the change in mass. Given the fact that the increase in mass slows the open loop response of the physical system, I would expect that it will still behave, but you must test this to be sure. I'm confident that any stability issues could be handled by modification of the servo feedback compensation.

If your goal is to allow for 14" masters, then you should be able to accomplish this by sistering a larger platter to the 1200. Since the 1200 wow, flutter, and rumble specs are good, I don't see the why you need to improve on them.

The big issue using a 1200 for cutting is the lack of reseve torque needed to deal with the drag presented by the cutter. This does not change with the high mass platter.

As Op indicates, you are probably better off starting from square one. Look for a higher torque turntable as a basis or roll your own.


Mark

Mark

[opcode66]

That's not exactly what i said. I said the platter likely couldn't start on it's own with that much weight. I also said it would have a harder time maintaining consistant speed. Because yes, once you apply the cutter head there will be drag. There isnt enough torque in a technics motor to counter the drag on that much weight. You can say I'm wtong all you want. That doesn't negate the fact that even with Souris platter on a 1200 records cut have noticeable flutter. If you like I'll send you one of the cuts. It's useless to me sonce it has audible flutter. It was cut on a vinylrecoder. Which is a lathe based on a 1200. You can order a special platter for it. Makes little difference. High torque and a heavy platter is what you want.

You say that it would just be more weight on the bearings. Have you ever disassembled a 1200? I have. First, the coils could never handle tge juice you would need for real torque. Second, there are no bearings. There is is a singular bearing if you can even call it that. The bottom of the spindle is rounded and fits into a cupped depression. A small amount of frease is applied to the coupling. That's it. The more weight you put on that "bearing" the more it will rummble as it turns.

A 1200 is a horrible platfrom to start from. Especially if you have cad skills. There is no point starting there. And, I'm not suggesting finding a higher torque turntable. Im sugesting designing a plinthe, sourcing an off the shelf high pole brushless dc motor with motor control circuit, all coupled together with a high quality bearing system. Some are very low friction using either magnets or compressed air.

Anywho, I'd be surprised if someone had an accurate 3d model of a 1200. And if tgey did, I doubt it would be freely shared. But, stranger things have happened...

[markrob]

Hi Op,

I'm not disagreeing with your basic premise. That is, the 1200 will have problems once you add the drag of the cutter into the equation. It was not designed to deal with that kind of load. If you just want to add a heavier platter to the 1200 and use it for playback, you should be ok. Whatever torque the motor can produce will cause the mass to accelerate to its final speed. More mass added means more time to reach speed. If the 1200's bearings were frictionless this would be true for any amount of added mass, but in the real world, there is some friction due to the bearings and they will add some amount of extra drag as mass is applied. I'm sure if you went crazy, the 1200 would fail to start, but within reason, adding mass should be ok.

As far as a 1200 having no bearings, that's crazy talk. They may not be precision ball bearings, but there is some form of bearing that the platter rotates on.

Mark

[opcode66]

Again I ask have you taken one apart? I have many tomes to service mine and friends. Take yours apart. You'll see that the spindle i the center of the platter is the top of the "bearing". It is rounded on the bottom, coupled to a plate that has a rounded divit. The only thing in between is a dab of grease. The coupling is a greased coller attached to the bottom plate. Go on ebay and look for spare parts for a 1200. Specifically the spindle because that is the "bearing". Dont believe me, oh well. No worries on my end. Just try examining the innerts of one and get back to me on that...

[markrob]

Hi,

I don't doubt you for a minute, but that is a bearing by definition.

Mark

[flozki]

i would say the 1200 is one of the better plattforms to start with.

the motor is great. the tacho also.
all is needed is a better regulation and a 2-3 kg more mass. you need to add a small controller that gives additional control voltage for increased torque.
all the signals are there. we did tests and there is some reserve to increase torque.
of course you have to cool the chips. add heatsink to the chip
i dont know how much the temperature will increase with additional load.
but for all those non professional cuts the torque is just on the lower limit and 20-30% more would be great and mostly enough.

when we did kingston dubplatecutter we where very close to do it with a small pic. but lack of time and resources this project was never finished...

i personally would go for high pole brushless dc and good electronics. but for now i dont know any high pole cheap and easy available motor right now.
there are some from washing machines used for wind generators on ebay.
but you need to find a resolver solution. 1000 pulses per turn would be good or an analog tacho. all in all, quite a job.

a good bearing and vacuum for holding the laquer is easy to do if you have access to a reasonable lathe. check my pictures of disk-o-mat
there it has ball bearing on bottom and 2 high tech plastic bearings for low rpm applications. the shaft to the turntable has a hole and between the two bearings there is a tube for the vacuum. works great.
i would love to find a 22-26 pole stator package to change it to dc-brushless....


happy bricolage.

[markrob]

Hi Flo,

That's encouraging. When I start my next build, I'll look for a trashed 1200 to experiment with. I know that Matsushita spent a great deal of time and money engineering the drive system for this application. The tach in paritcular is a difficult thing to do correctly if you want accurate feedback. Am I correct that a beefier version this same technology was used in some pro lathe designs? Had you ever considered riping out the exsiting electronics and rolling your own driver and/or controller?

Mark

[flozki]

hello mark
no i never thought of using an external electronics.
i think then i can also do everything from scratch.....

if i remember correctly my technics motor for the neumann has only 12 poles.diameter 120-150mm.so do the winding is quite easy.
but i would go much higher.
you can find old 1975-1985 harddrives they have similar stators. or maybe new stator package...also some ceiling ventilator could be a base.

the jvc motor which is also dc brushless uses a magnetic track with the tacho signals and regular magnetic heads from a tape.

for me this was just at the time of the kingston dubplatecutter of some interest. and as i said we made quite some tests and saw that there is some potential.... but it was not too important to cut into laquers at the time so it was not on priority list. the simple modification we suggested (jvo came up with that) was alredy enough and consisted of 2 parts....

quite high on my nice to know wantslist is a professional torque measurment on a vms70. when cutting some heavy out of phase stuff with range from 60-150um groove-width.....
i think noone did that seriously before and i also dont have the exact figures whats reallly needed and how much a stock lyrec can deliver....
the technics sp-02 says 28kg/cm =2.74 Nm starting torque...
P=2xPi *n * M
P=2x 3.14 x 33.33 * 2.74 Nm =573 /60 = 10W
the overal sp-02 consumption is 270W and i assume its 50-60% to the motor. so max. 135-160W.
so with 160 W and 33.33 rpm we shoud need theoretically 45.8 Nm.

for me this difference is still an open question. or do i make a major mistake right now?
i got access to a professional torque meter but no time at the moment...
one day.....

[opcode66]

Like flo is suggesting (and as I originally suggested), possibly another motor is a better idea since you would need to re-engineer so much of a 1200 for professional cuts. And, that was what I thought you were going for. Your initial sentences spoke of "cutting masters". I.E. Professional mastering on a technics.

Ok since I happen to work in VFX for film and TV, I figure I might as well put some of that to use in my own pursuit of building a viable mastering solution out of the SL-1200MKII turntable, of which I own 3 pairs.

The idea being here is that the SL-1200MKII rumble can be reduced to a minimum if not eliminated and adapted for 14" master cutting.

The electronics in the 1200 is so engineered for its factory state that changing things like the platter will have an effect. Same with changing the resistors to increase voltage to the coils.

all the signals are there. we did tests and there is some reserve to increase torque.

This is a simple resistor swap. Adds torque. But, guess what the side effect is? Flutter. The electronics are no longer "quartz locked". In fact, on older models, the electronics were only "quartz locked" when the pitch slider was at exactly zero. And, if your pitch wore out (which they often do on dj decks) or it wasn't calibrated correctly (which often happens with used pairs from people who tried to do this themselves) then you're never technically at 0 when your slider was locked into the zero point. I've seen all sorts of technics in my day, in many sorted conditions. Anyway, you could potentially never be "quartz locked" on some older models of technics 1200 when the pitch was at zero for the reasons stated above. Just depends on how much love they had over the years. But, I digress.

If you need to do something as drastic as this

no i never thought of using an external electronics.
i think then i can also do everything from scratch.....

Why not start with a motor like this...

i personally would go for high pole brushless dc and good electronics. but for now i dont know any high pole cheap and easy available motor right now.

as I had originally suggested. Add an off the shelf bearing coupling system and your own custom designed platter, the only thing left to do is design the plinthe/case and use a readily available motor control system.



You can purchase off the shelf motor control systems. All your pic needs to do these days is tell the motor control package what speed to run at. You can usually even control torque. By simply sending bytes over sdi or i2c. It is almost brainless. These are highly accurate motor control circuits. Right off the shelf. This makes development time on your end nearly zero.

One example of a maker of such devices:

http://www.microchip.com/pagehandler/en-us/technology/motorcontrol/

Specifically Brushless DC control:

http://www.microchip.com/pagehandler/en-us/technology/motorcontrol/motortypes/bldc.html



Here is a descent shot of the center spindle/bearing component. It screws into place under the patter onto the metal base. The brass taper is the coupling for the turntable platter. The coils surround this part under the platter. You can see the receiving cup on the base plate and the rounded bottom of the spindle. There is a smear of grease in there. The collar is also lubricated (silicon oil or 3 in one oil works). The collar is in the top plate. This piece is exactly the same on every technics model that begins 12xx. I understand that this technically qualifies as a bearing. However, I feel that this could have been drastically improved upon. Especially given how long these were in production. A swiss bearing from a modern skateboard wheel probably does a better job than this configuration...



You know you could do some tests to see how the weight affects things very easily. Pull the platter off one of your turntables. Invert it, and put it down on another turntable with the slipmat removed. That would simulate added weight. You could then put a slip mat on top with ticks on it and use a strobe to measure accuracy of rotational speed. Or, use the ticks on the side of the platters.

You could do that with different drag scenarios to see if this is a viable plan. You could then do the resistor swaps to see what added torque does with respect to flutter. All without actually making a plate. Proof of concept if you will.

[gold]

i personally would go for high pole brushless dc and good electronics. but for now i dont know any high pole cheap and easy available motor right now.

i would love to find a 22-26 pole stator package to change it to dc-brushless....

Do you have an example of an industrial motor that would work?

I don't know much about motors. I understand poles in an AC sychronous motor like the Lyrec.

Do the poles in a DC brushless serve the same purpose? Or are the poles the points of feedback for the servo system?

[mossboss]

Poles are Poles AC or DC it matters not What flo is looking for is more poles therefore lower speed more torque
A 2 pole motor at 50 HZ will spin at 2880 while a 4 pole motor exactly the same dimensions will spin at half that speed at 1440 RPM providing almost twice as much torque and so on down the line
I have tried out ceiling fan motors the bearing design is fine in some of them but since the weight is opposite than it would be on a TT it is far to much work to get it modified
I looked at a Fisher and Paykel washing machine motor which offers great possibilities Strong and sturdy pulsed AC (from memory) about 16 poles but room to add more
The winding are flat against a back plate exactly the same like a floppy disc drive motor
It has a large diameter the whole motor is at about 14 inches but about 3 inches thick
I dont see that it would be hard to make this to work as it would only need a thrust bearing at the protruding shaft when up ended It has quite large bearings for radial loads as encountered in a front loading washing machine
So far in my search I have stopped at this as a very good choice
The only other one that has come close is a motor from a Miele washing machine that it is electronically driven from say 0 to 26000 rpm again by pulsing it but it has something like 30 odd wires going into it So it looks like it is a multi wound DC motor Did not go pass a very close inspection of it workings
Cheers

[gold]

Thanks. I see why a washing machine motor is a good choice.

I dont see that it would be hard to make this to work as it would only need a thrust bearing at the protruding shaft

Do you mean add the thrust bearing to the shaft on the motor to axially stabilize it or couple the turntable to the shaft with a thrust bearing?

I think the former. How would you couple the turntable to the shaft?

[opcode66]

There you go... Now we are on the same page here... And, the motor control chip listed above is the other component. Motor, circuit, bearing, and plinthe/case. All off the shelf for the most part. You can use a shrot standard 19" rack for the case as well. The only thing left is a custom platter and mounting a 12" tonearm.

[mossboss]

Paul
Either way it'll be fine, it depends what level of accuracy one needs wants
For a semi pro lathe I would have thought sitting a platter on top of this proposed motor it would be sufficient
Machining a taper on the shaft would be easy
A platter laser cut out of say 2" allluminium with a taper to match and a bit of finishing at the edge as well as some grooves machined on its face would not present any problems to an average machine shop
It will certainly beat any 40-50 YO machine as used by most today
Assuming one wants a professional setup with a minimum wow or flutter a sturdy mount of the platter on a plinth with its own bearings with a small auto torque converter between motor and shaft driven with a flexible joint would present the best solution
The oil in the torque convertor would prevent any mechanically induced fluctuations reaching the platter
A decent set of aeronautical spece'd bearings for the platter shaft with a vacuum universal pick up joint as well as a a hole drilled in the center would take care of the rest
Alternative,
A two piece platter with the bottom part of a say 2.5" thick slab of aluminium with the top face machined down by 1/2" with an edge of say 3/8" thick so as to make a dish like shape and a half inch top platter sitting in it and a small amount of oil in between would also be an idea to try out so as to minimise any motor induced unwanted vibrations, wow and flutter
It will work like a torque convertor the floating in oil top platter will not have any mechanical connection to the driven bottom which can than be driven direct from the motor minimising component count
Of course this would necessitate some extra machining on the bottom plate face Some concentric grooves of say 1/8" deep about 1/2" apart all the way from center out to the 3/8" wall so as to keep the oil in just above the depth of the grooves would be required
The top platter would also need a stepped insert of steel pressed in from underneath of say 1 1/2" in diameter x 1" (tapered) long at the bottom so as to sit in a mating hole with say 1-2 thou clearance but not touching The oil bath would see it driven and centeralised
The protruding part of this steel inset out at the top be machined down to 9/32" so as to take the lacquer as well as the vacuum pick up
Radial holes with matching vertical ones at the different diameters 10"-12"-14" sectors are easy enough to drill The radial holes blocked with steel balls punched in the aluminium
For an accurate cutter head drive I have looked at lots of standard items The best I have identified so far is a Mitutoyo height gauge
Extremely fine ground thread as well as a very solid base which can act as a screw motor base as well as a means of mounting
The slide is induction hardened which should provide years of cutting without any loss of accuracy
The ones graduated in .0000 are a bit more pricey but worth the extra $ Regularly available on ebay as most machine shops have moved over to electronic means of measurement making these lovely pieces of engineering marvel affordable for something like this
Food for thought
Cheers

[gold]

Chris,

I'm thinking about a high quality system like the SP-02. It seems to me that as soon as you decouple the turntable platter from the drive mechanism you have no way of knowing what it's doing. I guess the motor control can ensure the motor is maintaining speed with the servo but not the decoupled platter. Wouldn't you need the servo feedback to be taken from a sensor on the platter? I know Denon did this with a magnetic strip and a pickup. How does the SP-02 do it?

Paul

[djlithium]

Ok I should clarify one thing - the acrylic platter I'm proposing would also have grooves on the side for a belt to be attached to it so it can be turned by an external motor if you wanted. One for 33/3, one for 45RPM even. Don't have external motor? no problem, just cut on the deck as it is. Upgrade as you go.

The idea behind using the Technics SL-1200MK2 as a base was that it is an easy thing you can get off ebay or craigs list for a few hundred bucks, then add this platter extension thingy and you have the basis for a lathe that will do 14" master cuts. The whole thing compliment's the Caruso project to a degree. Now whats needed is the overhanging carriage for the cutting head and electronics. Goal being get Caruso, one of these deck platter extensions, the electronics and the overhead mechanics for under 4000 bucks. Awesome.

Keep in mind I DJ for a living and for entertainment. If I can cut my own stuff down to 12" PVC or other peoples tracks that I want to play because there has been a complete lack of decent material on vinyl in the trance genre lately (jerks at armada have ruined it!) - then this gives me that capability. Going to a 14" master sure, yeah ok.. maybe thats a bit over the top, but if I wanted to do it I should be able to and get decent results on my own. Half the stuff that gets pressed these days out some places, is mastered horribly and we still play it - so I don't think I can screw it up any worse than the next guy especially if I have the stuff myself to do it. MY goal here is to bring the ability for serious DJs like me to cut stuff down to PVC for limited use (how long does a dance track really have for play-ability anyway before someone gets tired of it week after week). Now I know you guys are all pros and stuff, and I totally appreciate that - but for the most part I think you are sometimes getting hung up on things that many people are much more forgiving of. So I think the SL-1200 is a good base to start from even if one is using its own motor to drive the platter rotation.

One technical hurdle at a time.
But think about it - everyone someone needs to do what I want to do, for under 4000 bucks. Flo' has made a great cutting head, but what's missing is the rest of the package for people like me to get into it. And a lot of people like me want to get into it - so lets figure out a way to do it with conventional, easily available stuff.

[flozki]

@opcode:

"flozki wrote:
all the signals are there. we did tests and there is some reserve to increase torque".


This is a simple resistor swap. Adds torque. But, guess what the side effect is? Flutter. The electronics are no longer "quartz locked". In fact, on older m

nope there are two differnet things.
there is reserve to increase the torque and keep the quarz locked.

changing resistor AND also a capacitor helps to make the window bigger for stable and locked operation.

but what i say with reserve is that if you add a simple microcontroller and wirte the regulation you can get more out of the regular electronics.


@mossboss i wish to have a source for the fisher and paykel motors.
i observed these motors years ago but never got one in europe. they where quite used for wind generators.
also i never found out which miele uses the dc-brushless. but it has to be a washing machine for under $400 otherwise it does not make sense...
actually i only need the 14-22 pole stator package. i can order and laser cut it for i guess 200-300 bucks. but no time right now. but with a plug and play motor i might will try again...

all the regular standard motor are not optimised for 33 rpm. ripple is way to much. i have a maxon 90W dc brushless on my desk. waiting for tests since 6 month. but i guess the electronics is also not optimised. for all standard solutions the key is the high res tacho. and this is missing on all of them. also the quarz phase lock regulation is not needed for industrial applications. so there it is necessary to have a custom electronics..
and optimised low ripple design. which no one needs except crazy guys cutting vinyl masters.

but yes guys
go for it. definitely the best thing you can put time,effort and money into.
we need a good motor. at least affordable. and if possible open source...

[Aussie0zborn]

How about the Garrard 401 turntable? The motor is huge although I dont know the specs on it. I gave one to an old friend to transfer some 78s and after he finished he.... sold it. They go for over $1,000 on Ebay.

One of the DJ product companies (I think Numark) claims to make a turntable with higher torque than the SL1200.