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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


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dover
2,247 posts
 
Toho plinth -

 I discovered vintage TOHO cast iron plinths online. I don't have technics Sp10mkII anymore. But Toho plinth for Victor TT-101 is interesting (not so big and not so heavy).  

What happens when the cleaning lady, sorry - non binary cleaning supervisor, decides to clean under the arm pod and forgets to tell you they moved it.

Answer - a year later you wonder why all your favourite records are mistracking.

I subscribe to the loop rigidity principle - platter, bearing & arm mount must be absolutely rigidly locked together in position  to measure the groove accurately. Arm pods in my view are only as good as what they sit on, and often will compromise loop rigidity
pindac's avatar
pindac
2,864 posts
 
@dover 
  I subscribe to the loop rigidity principle - platter, bearing & arm mount must be absolutely rigidly locked together in position  to measure the groove accurately. Arm pods in my view are only as good as what they sit on, and often will compromise loop rigidity.

This is where my mentors in Turntable Design have guided me to.
I stick with this Design Intent and see no reason to seek out an alternative method.
Plinth Materials that have very stable properties in an environment are key to this.
A plinth must have two properties in my view above any other:
1, It should not deform from its flatness across the different seasons and moisture levels being met in the air.   
2, It should not expand in any dimension due to different moisture levels being met across the different seasons.

If the Design for the Plinth is to have a materials which offers a Specific  Intrinsic Damping Factor Measurement and offer the above properties then Densified Wood is looking likely to be the material to offer these properties.

As for Stand Alone Tonearm Pods, much of my listening is carried out on other systems and one uses a Pod.  I don't  detect that any enjoyment of the music is lost, and it might need a very detailed analysis between the differing Tonearm Mounting Methods to produce an assessment of the Pro's / Con's where listening and perceived sound quality is the basis of the investigation.   
dover
2,247 posts
 
Pindac
If by denified wood you mean panzerholz or lignostone then it is not stable. The stuff bends. You would need to anchor it to some other material or structure to prevent warping over time.
I have seen some very expensive plinths that use panzerholz, and over time, you can see they are starting to come apart. 

lewm
13,108 posts
 
The lunatic billionaires in NYC are typically not New Yorkers by native standards and typically don’t actually reside in their mega-expensive apartments. Of course we know that one bona fide native NYer who is a self described stable genius and billionaire recently moved to Florida.
pindac's avatar
pindac
2,864 posts
 
I am familiar with Panzerholz used as a Single Board in 20mm and
32mm and I can safely say there is not any knowledge known to myself of it having any detrimental impaction on its properties in when solely chosen as the material for a Plinth.

As a material used for plinths it is most likely to have reports on its usage that have close to a 12 Years History and I am not as yet with any recollection of seeing an information being offered informing of the material being unstable and not suitable for Plinth usage.

I have discussed Panzerholz with a variety of Plinth Builders via Forums, Private Contact and Face to Face, I know some who have rejected it as a material for the Sonic Quality not being to their liking, but never for the deterioration of the material.

During a recent search for a Product from the same producer, I learnt that Panzerholz is also used as the Cabinet Material on a High End Speaker Product.   
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