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


128x128Ag insider logo xs@2xrich121
For looks alone, the Dobbins plinth is gorgeous. It looks like slate (which Chakster likes to call "graphite") but I think it is made from a synthetic material that has some of the properties of slate/graphite.  For what it's worth, Rich, and I think I have mentioned this before, by ordering my slate slab direct from the quarry, where they honed both sides to perfect flatness and even champhered the corners so as to give it a nice look, and then having it cut to fit the Mk3 by a water-jet company also in PA, I was able to make my slate plinth for about a total of less than $600.  Then I had the solid cherry base made by a carpenter for another few hundred bucks.  I bolted the slate and the wood together for max CLD effect, but gravity really does most of that work. I can help if you want to go a similar route.
I dont like plywood or panzerholz because they are dimensionally unstable in the long term - warping, expansion, contraction.

I have had excellent results with Engineered Stone ( 95% plus quartz for premium quality european product ). There are many kitchen benchtop manufacturers with the requisite CNC machines to ensure accuracy at modest prices, particularly if you use offcuts which most have from large jobs.

I have also used Ebonised Bamboo ply, this is a high density bamboo ply ( over 50% heavier than standard bamboo ply ) - it is 50% harder than maple. In this case I did the CAD drawings myself, and used a CNC contract cutter to do the cutting. You need very sharp quality router tips or blades to cut this stuff cleanly.

Both of these are relatively modest in price if you do the construction yourself after outsourcing the cut materials.





" I have much better turntables for my needs (I designed custom made racks for each of them), I happy that a question about plinth does not exist for me anymore (my Luxman PD-444 comes in super heavy aluminum stock plinth"

@chakster 

The Luxman PD 444 do NOT have a heavy aluminum stock plinth.
The weight is two thick steel plates
sandwiched over a piece of bloody particle board,  then epoxy glued to a thin sheet of brushed Aluminum for dress. Most of that 50 plus pounds is the steel.

Besides didn't you say forget the table it doesn't matter its only the cart to worry about? Yet here you are with more bloated bragadocios nonsense and incomplete incorrect statements paraded as fact..... I owned one 40 plus years ago and even I can remember its make up ....
I think the Individual in the Link knows a thing or three about P'holz.
Worth a read on what is referred to as Tank Wood (which their used term for P'holz)

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