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Thorens TD125 + SME 3009 II Fully Restored



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Thorens was a well-established Swiss brand of quality turntables long before
Linn and its peers appeared in the 1970s. The idler wheel drive TD124 remains
one of the revered tables among collectors today, with fully restored machines
on exotic plinths fetching many thousands of dollars. It's a fascination I can't
comprehend fully, perhaps never having listened to it's song, but the relatively
high mechanical noise from the motor seem to me difficult to tame and prevent
from affecting the sound quality.

The TD125 came a bit later, after Thorens had introduced the modest but successful
TD150, its first belt drive model, with a floating suspension similar to the
AR turntable introduced in 1961. The TD125 was intended to be the state of the
art for vinyl playback in 1968, and featured advanced features and build quality
that remains impressive even in this day of computer controlled lathes.

A decent quality sample of the TD125 came into my hands early this year. It
was not without issues, naturally, being a machine over 40 years old. It was
outfitted with a tonearm that has also achieved legendary status, an SME 3009
II. I already had a couple of Lenco turntables on the go in my workshop, as
well as a Thorens 160 and various other promising vintage turntables, but this
TD125 was such an interesting challenge that I decided to spare no effort to
bring out its former glory.

THORENS TD125 BASICS

The Linn LP12 has become the posterboy of all suspended subchassis turntables,
and most audio enthusiasts are familiar with the concept of a platter/main bearing
bolted on a subchassis that is suspended on springs riding on bolts which extend
down from the top plate. The motor is secured to the top plate and isolated
from the platter/tonearm by the springs and resilient belt. This is the design
invented by Acoustic Research , copied by Thorens in the TD150, and by Linn
in the LP12... and dozens of others since.

An Aside: Looking with the clarity of hindsight, the floating
subchassis introduced another variable for speed instability, the very real
possibility of relative movement between platter and motor, either due to external
shock, or transient increase in drag from a highly modulated part of the groove
or even a burp on the AC line. This has the potential to affect speed stability.
Awareness of such issues didn't escape the engineers of the time, surely, but
one thing the soft spring subchassis turntable did better than all its competitors
— when properly placed on a rigid stable table — was to avoid acoustic
feedback and reject external vibration. It was, at the time, so much better
than anything else, that perhaps the other factors paled in comparison

The TD125 differs from the orignal breed of AR, its own TD150 and Linn LP12
in a couple of important respects.



Scan from original TD125 brochure (courtesy of thorens-info.de)

First, the visible top plate in which the platter/bearing rides
is suspended, in a kind of reverse of the floating subchassis. You could call
it the floating main chassis, a massive cast alloy that weighs 7kg by
itself. A steel structure beneath this floating chassis has the motor bolted
on the left, and three plastic height adjustable cups which hold the springs.
Take off a couple of transit screws and a few ground wires, and the entire cast
chassis, with platter, main bearing and tonearm, can be lifted straight up and
off the bottom chassis. You'd have to be careful doing so as the total weight
exceeds 12 kg.

An exploded image of main parts from the service manual may help
visualize this.

The 16-pole AC synchronous motor is driven via a Wein bridge 2-phase
electronic circuit, which provide switching for 33, 45 and oddly, 16 RPM, plus
fine speed adjustment at each speed. The brushed aluminum control control strip
features stylized rectangular switches, including the cue control for the stock
Thorens arm. Strobe markings underneath the inner platter are viewed through
a lit mirror system from the front panel to check and adjust speed with ease.
Looking back at it today, it was clearly a tour de force of technology and design
in 1968. It sold when first released in the UK for £70, which translates
to about £1,136.52 in 2015, which is an excellent value considering Linn's
base model Majik LP12 sells for over US$4,000.

THIS TD125 SAMPLE

The plinth (wooden base) of my TD125 sample looked a bit beat up, and there
were lots of scratches on the metal control panel and slide switches. Here's
a quick visual tour of the original.



This Thorens TD125, when it first came into my hands.




With outer platter off.






Front left of plinth cracking.





The back stem of the SME 3009 II was sagging due to worn rubber bushing
within, the rubber grommets on the base mounting looked complete gone,
and it was covered with dust and grime, but... all in all, not bad.





The motor and metal parts looked fine, except for the yellowing of the
plastic motor pulley, which is harmless.






The motor electronics PCB looked OK, no leaky caps, but they're 40+ years
old. It is routine among electronics restorers to replace electrolytic
capcitors, which degrade fastest.





This crack on the inside of the back panel was pretty bad. It could have
been repaired by injecting the right type of glue in behind the cracks,
but since the veneer was in bad shape and it was only chipboard underneath,
I opted for a completely new plinth.

The main bearings looked OK under a bright LED flashlight, the platter spun
without discernible wobble even at the periphery (well under 0.5mm variance
over a complete turn), and the motor ran extremely quietly. So my initial goals
were:

  • Build a new, better, stronger plinth from hardwood, not veneered particle
    board.
  • Fit a strong bottom board to further strengthen the plinth.
  • Examine, clean & repair every part of the turntable and the tonearm.
  • Replace all the electrolytic capacitors in the electronics.
  • Find a way to eliminate or hide scratches.
  • Fine-tune, adjust and set up to make it sing again.

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The amount of wood needed to build a new plinth for a Thorens TD125 is small.
The stock plinth stands maybe 5" tall, and the perimeter of the turntable
is just a little over 5'. At my favorite local lumberyard, I found some very
nice looking wood from South America they call Jatoba. The salespeople assured
me the distributor was eco-certified, and this type of wood was very popular
as flooring for new homes in both Canada and the US. I took them at face value
and bought a 10' length of 1x8" rough hardwood. It was not expensive as
hardwoods go.

Later, I learned that the eco-certification of the distributer has little to
do with whether the wood is ecologically harvested, as the distributor may get
the wood from many sources who are less regulated. Chances are, most lumber
from South America is part and parcel of the clearing of the Amazon rain forests,
some 90% of which is done to create grazing land for raising cattle. Burger,
anyone? No use crying over spilled milk: I already had the wood, might as well
make good use of it.

The Jatoba wood was planed to just over 3/4" thickness with a small Mikata
planing machine on loan from Rob, my brother in law. The wood doesn't have super
smooth consistency; the grain is beautiful and dramatic, but changes texture,
making dense lumpy spots here and there. Much time was spent sanding. Face masks,
earplugs... they all got quite a workout.

After the wood was ready, pieces were cut with a table saw and a compound miter
saw to assemble a plinth with the same inner dimensions of the original. This
is mandatory for the TD125 hardware to fit properly. I used butt joints, but
with corner support in a deep inner groove that enabled the use of double 3/4"
thick Baltic Birch plywood to strengthen the structure. Only adhesive was used,
a fast bonding 4000 PSI strength cyanoacrylate — basically, a super glue
for wood.



Just sanded Jatoba plinth, in front of original.





After sanding and a couple coats of pure Tung oil. Later it was rubbed
with pure beeswax many times and buffed by hand and machine to a light
sheen.

Drilling the mounting holes perfectly for all the bolts to secure the steel
bottom tray and front control panel in place proved to be very tricky business.
The installation into the new plinth took a huge amount of time and effort,
elbow grease and fudging. In the end it got done, but not without many long
strings of expletives.















You may notice...

>> The platter rim is now polished to a mirror shine. This was not
my work, but that of a local outfit which does an outstanding job of such
metal polishing.

>> The rectangular slide switches are veneered with the same Jatoba
wood as the rest of the plinth. This was done by sawing thin slices with the
table saw, then cutting, shaping, and sanding the pieces to match the switches,
and gluing them in place. Removing the scratches on the original metal top
proved too difficult. I was also unable to remove the deep scratches on the
aluminum control panel. It would have required a complete re-brushing of the
surface, which would then require reprinting of all the lettering. Just too
much work and expense.

>> The bottom edge of the original plinth was inset and painted black.
I simulated the look with a full 3/4" thick Baltic Birch plywood bottom
cover, inset by about a centimeter. It was painted with four coats of flat
black.

>> The SME 3009 II tonearm was refurbished with all new rubber parts
from SME (which still stocks parts for these vintage tonearms), and a complete
rebuild of the cue lift mechanism to restore its smooth damped movement. That
was another ridiculous laborious affair.

>> The final dimensions are about 1/2" wider and deeper, and perhaps
an inch taller than the original. The total weight also went up, from about
37 lbs to about 43 lbs.



All new top-brand electrolytic capacitors in the motor control PCB.




Closeup of wooden switch covers and strobe at 33 RPM.

The reborn Thorens TD125 + SME 3009 II tonearm + Linn Adikt moving magnet cartridge
(from my old Linn LP12) became my primary record player for several months.
It was a pleasure to view, handle and listen to records with. Alas, the pressure
of my ongoing TT restoration "line" proved too heavy, and it was eventually
sold to a local buyer whose retail dealer found my listing on ebay. I'm glad
I didn't have to pack it for shipping!

Bob McKay, the new owner, wrote:

"It's mine now :) Listening to it while I type this. I mated a Shure
M97xe cartridge to the SME and it sounds wonderful.

"I purchased the Shure from Innovative Audio and had them mount it.
They were very impressed with the restoration work Mike did. There was comments
about how the platter seemed to be floating on air and how perfectly the suspension
was set up. I think they were drooling over the SME tone arm as well. It's
a beautiful table.

"To any who doesn't know MikeC, I found Mike to be amazingly knowledgeable
and passionate about turntables, such as the Thorens I bought from him. He's
provided me with a wealth of information to read up on. The pictures here
don't do it justice, it's really an amazing piece."

Thank you Bob. :)

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