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Technics SP10 MK3 Restoration

Just got my SP10 MK3 base (motor unit & controller) back from JP at FidelisAnalog.com
JP is one of the most knowledgeable on the SP10 MK3 and is the one who designed and manufactures the MN6042 Speed Control chip that keeps these and other Technics turntable models still operating.

My SP10 MK3 came with the stock Technics SH-10B5 faux obsidian base.
It has very low hours of use , no signs of wear at all on the bearing and not a single blemish, other than some specs of dust and a couple spots on the copper part of the platter that need cleaning.
but I would like to have a 2 arm, constrained layer plinth built and have the motor unit mounted 'naked'. I am presently searching somewhat 'affordable' plinth builders and suggestions would be greatly appreciated.

The work that JP did to both the motor unit and the controller:

1.       Pre-refurbishment measurement to baseline the performance of the unit and to see if there are any underlying issues.
2. Cleaning of all PCBs to remove the factory conformal coating. At~40 years this coating tends to become hygroscopic which can cause stability issues.
3. Physical inspection of all solder joints under an inspection microscope. Many of the joints will exhibit annular deformities which can lead to joint fractures down the road. These must be cleared of the factory solder and re-soldered. There will also be poor joints that need the same treatment. You can’t just reflow as the solder alloys aren’t the same which can also cause joint failure down the road.
4. Electrolytic cap replacement and rectifier diode replacement.
5. Disassembly and cleaning of the motor. Bearing inspection and service work. Proper Anderol 465 oil is used for reassembly. Motor is then checked for any areas of bearing drag.
6. The brake solenoids typically needs cleaned, and band tension is adjusted.
7. Stop/start and speed selection switches in the motor chassis are measured for contact resistance. Too high of resistance is indicative of a switch failure in the future. In the control unit I typically replace all the tactile switches, and the start/stop switch if needed.
8. Relocation of the brake regulator transistor to the heatsink to prevent overheating of the board (factory design flaw).
9. MN6042 replacement installation.
10. PSU ripple check at all critical stages (10).
11.   Course calibration is performed and post-refurb baseline measurements for FG spectrum, motor drive phases, etc. are taken.

12.   After 48-hour run-in final calibrations and verification measurements are performed.

The basic service returns the unit to factory or better specifications (assuming no permanent bearing damage has occurred).   This service is quite exhaustive and very different from the typical work I see of just swapping some caps out, checking some voltages, and adjusting phase tracking.

The advanced service adds on top of the basic service:

1.       Replace all polyester capacitors.
2. Replace drive circuit metal oxide resistors.
3. Replace all voltage regulator ICs and update circuits.
4. Replacement of certain diodes.

Rick


rich121
chakster's avatar
chakster
6,144 posts
 
This is a good chuckle.


@au_lait

Do you know who is the author?


Because if you ever read this Romy The Cat blog you can see the attitude of this Russian guy a bit better. For example, you can simply read his opinion on Denon 103 and I’m sure so many audiophiles will be offended :) There are more in his blog.

What I don’t really understand is why someone criticize other people Sound System in public after a personal visit, he even posted something about Jonathan’s wife and classical music, but not everyone is into classical music in 21st century! He posted a picture of the vintage horns from the actual Oswald Mil house in Pennsylvania, not the OMA hons from his NYC showroom!

As I said let’s be honest. Jonathan clearly explained in this video that he filled up his house with vintage tube electronics, horns, turntables and all that stuff for his own delights! He’s a collector of vintage analog gear first and then a founder of his own company. But I believe his real passion is vintage analog gear. He’s also a film maker.

He explained his background on OMA site, it’s an interesting story and many images of the manufacturing process of OMA equipment etc. Actually, far more interesting than reading a blog of that audiophile Romy The Cat who can’t even hire a web designer to make his posts readable and his blog navigation more user friendly, but Romy The Cat, who listen to classical music, criticize people who design beautiful things and running the biggest showroom open for public in NYC (everyone can visit).

solypsa's avatar
solypsa
462 posts
 
As usual this thread kinda veered off topic. OP wants a plinth. It sounded at first like OP wants to remove the outer chassis and just use the motor? Iirc...

There was a guy in Japan that did this using a light weight balsa like wood. Anyone remember his name? It just goes to show how many ways to slice the 'plinth-pie' :). Heavy, light, stone, wood, metal, mix...

I wonder how a stack of that carbon fiber balsa-cored paneling would do? Very stiff and light so resonant freq on the higher end I would imagine...could alternate direction of carbon and wood grain.



lewm
13,774 posts
 
solypsa, There are many aftermarket plinth makers who can remove an SP10 Mk2 or Mk3 motor assembly from its square-ish surrounding escutheon and mount only the motor assembly in a plinth specially designed for that purpose.  I think OMA can do that.  I know that Steve Dobbins was among the first to do that.  Probably others can do that too, for a price.  The process requires re-locating the on/off switch and the speed selector switch to some other outboard location, so it is not for the amateur. 


As to balsa wood, I am a firm believer that the very high torque motors of the SP10 MK2 and especially the Mk3 are best off in a high mass plinth.  Otherwise, there is the possibility for the tail to wag the dog; the very high torque puts a rotational force not only on the platter but also on the motor assembly.  Nature does not care which of the two rotates.  You want the torque to be used to push the platter, only.  So the plinth should be high in mass to resist motion.  Balsa wood need not apply. This is my opinion.  Others may disagree.  That's OK with me.
chakster's avatar
chakster
6,144 posts
 
The process requires re-locating the on/off switch and the speed selector switch to some other outboard location, so it is not for the amateur.
 

I remember Technics remote control with same on/off button for mkII version
rich121's avatar
rich121 OP
187 posts
 
@lewm

Only the motor unit with cable needs to be mounted to the plinth, as none of the controls on the original face plate are needed/used... all control will be from the remote control.
I don’t think it to be any more difficult... just will need an additional layer of material to surround the platter as a top plate.

Also totally agree with the plinth needing mass, either slate or constrained layer panzerholtz/baltic birch or maybe even Delignit/Panzerholtz and baltic birch?


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