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Thorens TD124 sn 33389 (late first version)

Receiving:

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Inspection, Visual:

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Disassembly

DSC_2997.jpg (260434 bytes)  Note the screw heads holding the motor together have been buggered up by using the wrong sized screw driver.

DSC_2998.jpg (351213 bytes) Factory original solders on this voltage commutator.  No one's touched it.

DSC_2999.jpg (387812 bytes) Just a shot for reference. Motor on/off switch....later version...and my preference.

  

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1:Idler wheel carrier assembly.  The cam follower end with that slotted set screw all buggered up..... The screw will not budge and the screwdriver slot is beyond use.  I'm soaking in some ATF to get penetration into the threads in hopes that this may loosen the frozen set screw.  But it refuses to loosen up and remains tightly frozen.  So...we get to photo #2: Using a pin vice style finger drill and a set of small diameter drills I progressively drill into the screw without touching the threaded walls in the collar. And, eventually we get to photo #3 where we see that there was success in drilling out the frozen set screw.   The threaded wall in the collar remained unharmed by the process.  Photo #4 is the other threaded hole in that same collar.  Btw, this carrier assembly does allow some adjustability for idler wheel height by means of the 'pin end' distance beyond the set screw collar. With this distance set during assembly.  But when this assembly is correctly set, it is better to adjust idler wheel height at the two other remaining points of adjustment.  I'll highlight those during the assembly process further down the page.

DSC_3004.jpg (318287 bytes) The chassis, stripped of its mechanical bits as far down as is needed.

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DSC_3008.jpg (289031 bytes) Parts organized into component assemblies and then bagged.

DSC_3009.jpg (312917 bytes) underside. 

 

 

Inspection; mechanical and metrology

Idler wheel and associated components:

DSC_3010.jpg (508827 bytes) DSC_3012.jpg (443240 bytes) idler wheel, looking at the rubber

DSC_3016.jpg (117643 bytes) and the rubber where it meets the business. Note: TD124 idler wheels tend to not suffer flat spots as do other brands, due to the overall design.  However the rubber does age and as the rubber loses its 'freshness' performance can suffer.  ime this one appears marginal.  Still useful but if the goal is 100% like-new performance, then the rubber needs to be new.

DSC_3013.jpg (312759 bytes) wheel with its supporting structure

DSC_3014 anno.jpg (404550 bytes) measurements:

bushing sleeve ID: 0.1978" (note: units = inches, decimal)
axle pin OD: 0.1966"
running clearance: 0.0012"
thrust washer = present and ok

Idler wheel carrier support.  There is a precision-ground and hardened steel pin that operates vertically in a chassis-mounted bushing bore.  This feature controls position of the idler wheel relative to the stepped pulley that drives it. The pin diameter here is the same as the axle pin for the idler wheel at .1966.  The bushing bore in the chassis measures from  .1985" to .2010".  This much clearance is fairly typically of what I've seen in the other td124 chassis that have passed through here.  A running clearance between pin and bore ranges from .0019" to .0044".  If you combine the operating clearance between the idler wheel axle and bore plus the carrier pin to bore clearance we see as much as .0056" of slop in the positioning of the idler wheel relative to the stepped pulley.  Aware of this I will observe the idler wheel behavior at assembly and while operating to see if there is any visual evidence of excessive slop.  And while remembering that the wheel ,must adjust itself in position not only to the stepped pulley but also the inner platter rim which it drives.

DSC_3018.jpg (241737 bytes) DSC_3019.jpg (243101 bytes)  Fractured on/off -speed select knob.  (material: bakelite with bronze bush insert.)  Whether or not these cracks widen depends upon how much load the knob carries as it is operated.  This load will be reduced once the speed select related components are cleaned and lubed, however I regard the condition of this knob to be close to absolute failure once put back into operation.  Perhaps the cracks can be repaired and strengthened by filling the voids with an epoxy based adhesive.  Or perhaps a decent replacement can be found.

DSC_3020.jpg (457084 bytes) Knob and pitch adjuster. The good news; the pitch adjuster still looks ok ;-)

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Main bearing shaft diameter: .5500 - .5501"
bushing sleeve id: lower: .5513"
bushing sleeve id: upper: .5515"
running clearance shaft to bore: .0015" max

DSC_3030.jpg (347978 bytes) notes bearing shaft: macro close-up detail photo indicates that this bearing shaft has been polished once before.  Note the diagonal cross-hatch light abrasive marks all over.  The black areas, I suspect, are residue from having been treated for rust.  This occurs when an anti-rust treatment such as Naval Jelly is used on rust.  The Naval Jelly converts the rust into the black that is seen. Some of this 'black' can be scraped off with a fingernail.  I'll attempt to clean it.

The bushing sleeves in the housing can be replaced as a matter of course.  The larger measurement at the upper sleeve is typical of the wear pattern seen in many record players where the upper bushing takes a greater load from the driving idler wheel.

motor:

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Rotor shaft measures: range: .1868" to .1869"

DSC_3040.jpg (225881 bytes) After clean, motor parts in the plastic tub.

cleaning cycle re: the rotor bushings:
soak in lacquer thinner to loosen and wash old dirty lube
oven bake at 250F for 30 minutes
use Q-tip soaked in acetone to wipe any lube oozing out of the bore after the oven bake.  Considerable dirty residue shows up on the Q-tip.
oven bake at 250F for 30 minutes
use Q-tip soaked in acetone to wipe any lube oozing out of the bore after the oven bake.  Considerably less residue shows up on the Q-tip
oven bake at 250F for 30 minutes
use Q-tip soaked in acetone to wipe any lube oozing out of the bore after the oven bake.  This time, very little residue shows on the Q-tip

Measure the bores (with a Mahr bore gage as noted above this page)  of the two rotor bushings for size and evidence of irregularity.  Result: size in both bores: .1879"  Round and no evidence of taper or irregular wear.

Running clearance between rotor shaft and bushing bores: .0010" to .0011"

 DSC_3043.jpg (113075 bytes) Lube cycle.  Soak the cleaned bushings in a bottle of the lube to be used.  20wt turbine oil.  aka Thorens oil. Texaco R&O 46/

DSC_3045 anno.jpg (183914 bytes) stepped idler and housing
stepped idler axle pin measurements: pin diameter .1574
stepped idler bushing bore: .1582
running clearance: .0008"
thrust pad: 1 unused side remaining

Cleanup

DSC_3021.jpg (485757 bytes) b4  DSC_3047.jpg (488054 bytes) after

DSC_3048.jpg (359841 bytes)  After using a green nylon scuff pad on the 'rusty' paint within the underside area.

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Assembly trials

DSC_3056.jpg (179147 bytes) Parts from AudioSilente: nice new mushrooms, MKII conversion kit, bronze brg end cap.

Parts from The Analog Dept: Torlon brg thrust pad. (main platter brg)

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DSC_3060.jpg (203903 bytes) DSC_3061.jpg (273573 bytes) DSC_3062.jpg (238027 bytes) Parts from The Analog Dept: fasteners, Torlon Brg thrust pad. (E50)

More of the assembly process will be shown when the parts ordered from Schopper arrive.  Meantime, I'm using the parts from AudioSilente , The Analog Dept and existing to get an early listening session in.

The replacement on/off lever arrives from The UK:

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Thorens used the same lever and pitch knob on the models TD111, TD121, TD124, TD134, TD135.  (This style is the mk 1.)  I suspect the pitch control parts shown that came with the replacement lever were from a TD111.  As shown, the shaft fixed to the pitch knob uses a collar with two set screws to locate it.  On the TD124 the pitch knob shaft has a e-clip groove that is used to retain it within the pitch adjust assembly.  Slight variations.  But the lever will do the trick just fine.  Now we've got a good speed change lever!

Next day the Schopper parts arrive:

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The new idler wheel from Schopper also includes their Idler Wheel Noise Reduction Kit.  The kit includes a vial of their 'oil', a circular plastic cup and a thin rubber pad. We will follow the enclosed instructions for handling and assembly of these parts.

DSC_3071.jpg (237309 bytes) After 15 hours of record spinning time, 33389 finds itself in the service jig again.  The fractured on/off knob has been replaced.  The original pitch control knob is retained as are the pitch control assembly pieces.  The main platter bearing has been disassembled to inspect the shaft and bushings for any evidence of distress after the 15 hr. run-in period.  Both shaft and bushing bores appear fine.  The Torlon thrust pad doesn't yet show any indentation from the vertical thrust forces normal to its operation.  The shaft is re-assembled into its housing and bides its time until the iron platter is assembled onto it.  The original idler wheel is removed to make room for the new Schopper idler wheel.

DSC_3072.jpg (195839 bytes) The new Schopper belt is installed.

DSC_3073.jpg (195723 bytes) The Schopper idler wheel noise reduction kit uses a rubber pad installed as shown.

DSC_3074.jpg (193601 bytes) Then there is this plastic cup with a concentric bore designed to fit it over the idler wheel axle as shown.

DSC_3075.jpg (193358 bytes) The original thrust washer is maintained in this assembly. It resides down into the bottom of the new cup.  Apart from that the noise reduction kit comes with its own vial of lube.  This lube is quite a bit more viscous than the 20 wt. lube used elsewhere on the deck.  The idea appears to be that a small pool of lube is maintained in the bottom of the cup.  Instructions say 1 to 2 mm thick, no more or things could get messy.  Looking at this setup, I understand the concern.

DSC_3076.jpg (227633 bytes) And now with the wheel over the axle and into the lube-filled cup.  Some of the same lube was drizzled over the axle shaft before mounting the wheel.

DSC_3077.jpg (199281 bytes) And with the retainer collar mounted.  The thin phenolic shim washer is just under the collar.  In the photo the drive train is spinning the idler wheel.  You might notice the blur.  This wheel spins true both for concentricity and for vertical run-out.  In fact one of the truest running idler wheels using the original design I've seen.   It looks and spins like a high quality wheel. Money well spent.

DSC_3078.jpg (308820 bytes) DSC_3079.jpg (322497 bytes) In the two photos you can clearly see the brass end cap from AudioSilente.  During the 15 hour run-in there were no leaks.

DSC_3080.jpg (315787 bytes) Showing the electrical cord connection. The chassis is grounded to the building ground by this arrangement.  A three prong cord is used.  18awg copper with a UL tag.  This is really a computer power cord with the IEC connector removed. 

DSC_3081.jpg (155624 bytes) DSC_3082.jpg (150719 bytes) After having numerous TD124 units come through here I have observed that the iron platters were machined to tight tolerance and can be expected to maintain close concentricity to the bearing shaft upon assembly.  The mkII zinc platters are a different story and require dialing in using a dial indicator when mounting one of those.   The iron platter will be removed prior to shipment and the owner can mount the platter and secure it with the three substantial machine screws that retain it.

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Notes: The motor and its associated electrical parts are healthy and exhibit robust operation. 

 Chassis: Threaded holes within the chassis.  I found some damaged internal threads as follows:

One of the two threaded holes that secures the clamp over the neon lamp fixture showed evidence of broken internal threads.  No photo.  I used a M3.5x.6mm tap to repair this threaded hole.  It was successful with the result that the machine screw can now thread in and out normally.
One of the 3 threaded holes that secure the tonearm board showed evidence of obvious cross threading.  (nearest the tonearm counterweight end) The result being that the M5 armboard screw would thread in easily, except at an angle several degrees off the vertical, then the screw would stop solid about 8 threads in.  Solution, using a clean M5 screw, thread in from the opposite side, with plenty of lube oil.  This has the effect of straightening out the crooked thread which now receives armboard screws as it should.
All threaded holes in the chassis were dry with no trace of lube.  However some of the machine screws showed evidence of a rust build-up within their external threads. Corrective procedure; clean all machine screws of any traces of rust, then apply lube literally to all threaded holes within the chassis and to the machine screws that mate.
Lesson to be observed: The TD124 aluminum chassis is a soft material.  And the aluminum will easily be damaged at its threaded features.  USE CAUTION WHEN ASSEMBLING THREADED FASTENERS ON A TD124 CHASSIS. Every time.
On the subject of threads, the machine screws are of an older design and specification common to Switzerland /Europe in the late 1950's.  The slotted screws in many cases have a slot that is narrower than slotted machine screws commonly used in North America.  If your screw driver does not fully seat into the slot, do not operate the screw.  Instead get a screw driver that does fit. (go buy one) or file down one of your more expendable screwdrivers so that it will seat fully into the slotted heads of these screws.
The pitch control is a tad stiff. I found that the end of the adjuster shaft had been buggered/gouged by the set screws that hold the collar.  I used fine gage sand paper to remove the high spots on that shaft end.  This helped to improve the pitch control action somewhat as that tiny little roller that functions as a bearing to the positioner link now rolls smoother when pitch is being adjusted.  At this point pitch adjust function is correct and will stay that way.
I will remove the lube from the idler wheel noise reduction cup prior to shipment.  Otherwise the --up-down-upside-down and sideways -- journey will likely cause a spill.  The owner will need to install new lube when setting up.
The iron platter will be removed from the top of the bearing and stored below the deck in the shipment box.  This will reduce box height by a good 6 to 7 inches.  It is how Schopper ships their TD124s to their customers.   Also it is much easier on the bearing bushings and thrust pad to not disturb the fit between them and the shaft.
On the subject of platter the platter bearing, it has a very good fit between shaft and bushing. The 15 hr run-in, which was done to test all drive train components, indicate that the shaft, as pock-marked as it is, is mated well to the housing assembly and also working quite well.  I anticipate a long life for it, if the owner doesn't replace both bearing and platter with higher end upgrade parts.
The Schopper belt is installed and working as expected. This one is my favorite TD124 belt.
Upper platter.  Delivered to me as a very nice, almost perfect, specimen.  Straight, flat and with good finish.  The rubber platter mat is also good.  I removed the 45 adapter/bearing/mat retainer center fixture and removed the mat.  However, removing the mat was not straight forward.  Someone had used a light duty transparent adhesive, such as Elmers School Glue, to adhere the mat to the aluminum platter.  The adhesive residue removed easily by holding the platter under warm running water in the sink.  I cleaned the rubber mat with dish soap and warm water.  Then I put to boil 4 quarts of water and poured the boiling water over the cleaned mat while it was in the kitchen sink (sink plugged).  And then let the mat soak in the hot water for 5 minutes.  Then dry and reinstall mat to the cleaned upper platter.  And the upper platter was already clean.  So, I just inspected, I guess.  If the owner wants to put more of that light duty adhesive between mat and platter, I can't see anything wrong in that.  If it helps dampen the upper platter, so much the better.  I may try it on mine.  Nice idea.

All that is left is for me to provide a suitable foam-filled ship carton.

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