hobbyists's views for hobbyists The Thorens TD 124 Page

© Rudolf A. Bruil - Page first published on the www in August 2001.

 

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Introduction

	TD-124 and TD-124Mk2 Do you own a Thorens TD 124 or TD 124 Mk2? And do you have the original manual? And maybe you do know a lot about your TD124? So much the better. Maybe this page is not for you. It cannot harm however to look at the images and read some important facts. Many visitors of my website and many Thorens lovers have asked me about the TD124 and TD124Mk2.TD stands for "tourne-disque" which means literally "record turner" in French. The Thorens TD124 has an iron cast platter weighing 4.3 kg, sometimes a bit more. It is driven by a relatively strong 10 Watt motor. (The Garrard 301 has a 16 Watt motor.) The rotation is transmitted via a belt to a stepped pulley. The 4 steps are for the 4 speeds: 16 2/3, 33 1/3, 45 and 78 rpm. The turning of this stepped pulley is transmitted to the inside of the rim of the platter via a rubber wheel.
	ORTOFON On the upper left you see the first TD-124 with the long SME 3012 arm and the Ortofon SPU-GT cartridge in an early Ortofon headshell with its particular shape. The shell pictured on the left is a later version which is generally known.
	TD-124 MK2 It is a combination of a belt drive and an idler wheel drive. The TD124 has 4 speeds: 16 2/3, 33 1/3, 45 and 78 RPM. These speeds can be adjusted which is great for people with absolute pitch, for those musicians who want to play along with a recording without having to tune their instruments, and for the playing of shellac records which are not always engraved at 78 RPM but have different speeds up to eighty or even higher RPM. The platter of every TD124 is topped by a light aluminum sub platter. The adapter for 45 RPM discs is integrated. It has a spring and when you push it lightly and turn it to the right it moves up. When you push it lightly down again and turn it to the left, it will lock and stay put. The pattern of the rubber turntable mat consists of closed rings.
Thorens TD124 Mk2 and new TP 14 arm	TP-14 ARM The TD-124Mk2 has a more modern styled frame and the turntable mat has fewer rings which are interrupted and a new arm, the TP.14, which replaces the earlier BTD-125 arm. But the most important aspect is that the app. 4.395 kg weighing iron platter could be replaced on request by a 3.63 kg. platter of aluminum which of course is non magnetic and thus does not attract a heavy moving coil cartridge with a strong magnet. The TD124mk2 was described by R.L. West in his review for HiFi News of July 1966: "The TD.124 has long been recognized as the Rolls-Royce of transcription motors. It is as solidly made as our Garrard 301 and 401, but has one or two special features of merit. The Garrard takes its drive from a stepped pulley on the motor via a rubber-tyred idler to the turntable. The Thorens interposes a light flat rubber belt between the motor and the separate stepped pulley which drives the idler. This stepped pulley is solid with the main frame, and so prevents any motor vibration , whatever its direction, from reaching the turntable via the drive. (...) Altogether, a very sound machine, still being made just as carefully. (...) The TP.14 arm measurements are most impressive and show Messrs. Thorens are fully awake to the modern need of arms that will behave perfectly down to stylus pressures of below 1 gm if so desired."
	BEOGRAM 3000 The TD-124Mk2 was soon recognized as one of the most sophisticated transcription turntables available on the market. Both Bang & Olufsen (B&O) from Denmark and Tandbergs Radiofabrikk from Norway choose the TD-124 MkII to be incorporated in the top of their product line and the turntable was adorned with their respective logos. At left the Beogram 3000 with B&O tone arm and cartridge. (Edited picture taken from an advertisement in a Dutch record magazine from 1969.)
	4 SPEEDS This is a picture taken from the instruction manual of an early TD 124. The armboard did not have a black coating yet. When the 16 2/3 speed was proposed in the mid nineteen fifties many manufacturers incorporated the speed into their gramophones and turntables. Right from the beginning the TD 124 also had 16 2/3 rpm which was meant for recordings containing speech and was really not suitable for high fidelity. Note: The aluminum platter which later could be ordered has only 2 stroboscope rings for 16 2/3 and 33 1/3 respectively. It goes without saying that if you have to adjust the downforce of a cartridge when using an iron platter, you have to place the scale not on a record but directly on the rubber mat to get a more exact reading. If you just turn the counterweight to the desired marking when the arm is away from the platter's periphery, or placed on the rest of the lift, you will get a faulty result!
	BELT DRIVE AND IDLER WHEEL The TD-124Mk2 had a more modern look but the combination of a belt driven pulley and a rubber idler wheel of the original TD-124 was of course retained and the heavy platter is turned with the same minimum of wow and practically immeasurable flutter. Rumble values are also exemplary. That is if the bearing functions perfectly well, if the rubber belt is not damaged and not too loose, and if the motor is well de-coupled from the main chassis by three sets of two rubber rings/grommets. The player should be decoupled in some way from its surrounding by means of rubber insulators (originally the mushroom-shaped insulators), or if placed directly on a stand, the stand should have spikes or cones (spikes are preferred). Also the table should be level at all times to function well. See also Turntable Adjustment.
	VERSATILE MACHINE The design, the sturdy build, the specific features no other turntable had, and the precision with which each and every TD-124 was manufactured, made this turntable about the best a man could get. Serious music lovers and audiophiles alike were very fond of this transcription turntable and combined it with tone arms from Ortofon and SME, and with cartridges from Shure and Ortofon. At left an advertisement from 1961. It was published in the April issue of High Fidelity magazine in the US. By that time Thorens products were imported by Elpa Marketing Industries Inc. They also imported Revox tape recorders. An advertisement from 1960 did not mention Elpa Marketing yet. The cost of $99.95 for the TD-124 is amazing, at least measured by non-American standards in that era. The dollar was a strong currency with a high exchange rate. $99.95 for a unit to be built in a cabinet or to be mounted on a plinth are peanuts today. The copywriter's text: "Thorens compensates for variations in house current and recording systems; gives the truest reproduction with all your records, old or new. Adjustment is so fine that records can be used to accompany live vocal and instrumental performances. Swiss precision engineering ensures longer record life, performance to match the finest components you will ever own." The Thorens TD-124 was in the nineteen fifties and sixties what the Technics SP-10Mk3 was for the early nineteen eighties, and to a lesser extent the SP-10 Mk2 for the nineteen seventies - if you consider the variable pitch a necessary feature. It is amazing that many a TD-124 transcription unit is still in use some 50 years after the introduction. It takes some attention and knowledge to keep a TD-124 up and running satisfactorily. The die hards know how to service the mechanism and treat the machine with care, and they eventually substitute one part or another, if necessary: a new idler wheel, a belt, a better spindle and bearing, and maybe a platter. Others just own a TD-124 because they consider it as an antique object and do not bother much about the proper functioning. In any case the paragraphs that follow can give you more insight and ideas in order to fully enjoy the working of this turntable.

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The Idler Wheel and The Specifications

	VALUES For his review in HiFi News, audio journalist R.L. West meticulously measured the parts and the functioning of the TD-124 Mk2 and compared these data to the measurements on his 4 year old original TD-124. The platter of the Mk2 weighs 8 lb (3.63 Kg). Of course he did not want to weigh the platter of the first TD-124 as this would mean taking the platter off the frame. The spindle is the heart of the matter. Machining it with close tolerance is of the utmost importance. The spindles of the TD-124 and the TD-124 mk2 measured 0.2824 inch and 0.2822 inch respectively. Values for turntable bearing slack measured +/- 0.0015 inch. Wow and flutter was estimated at 0.05 or less than 0.05%. It is unlikely that the polished hard steel spindle will show wear from years of turning. However, the relatively soft sinter bronze bushings can give way to the pressure of the spindle and the turning during decades of service, especially if the machine is not level.
	CENTERING THE PLATTER In case you have bought a new spindle and bearing from Schopper or have a new bearing housing made by a machinist, you will have to insert the spindle (axis) into it. Also if you disconnected the spindle from the platter, you would need a measuring instrument to calibrate the platter the way it was done in the Thorens factory. Naturally the calibrating was done on the inside of the rim, there where the idler wheel touches the platter and where the precise centering is the most effective. In the picture at left it is shown how it was done. If you did separate the spindle from the bearing for whatever reason, see to it that the spindle is completely lowered into the bearing before you place the platter on it. Use a Record Weight to speed things up. But do not force the lowering. After the spindle has completely sunk into the bearing, you carefully place the platter on the spindle and center the platter. At left you see the technician checking and adjusting the precise turning of the green painted platter of the TD-124. The platter of the Mk2 was made of aluminum. The image at left was sent to me by Joachim Bung. It appears in his extensive books Schweizer Präzision and Swiss Precision, with the fascinating story of Thorens, its competitors and its history. Click on the link to know more.
	CARPENTER'S EYE How do you center the platter? Many of you owners have of course found out the best method of checking the correct centering of the platter by using a calibrating instrument. But what if you do not have access to such an instrument? First of all you need a carpenter's eye. Then take a rectangular object, a wooden block or a piece of aluminum, or whatever is suitable, and place it on the armboard. Do not fix the platter to the spindle yet by tightening the screws. Now bring your eyes level with the platter and the rectangular block. Turn the platter slowly with your hand and check at what point the platter is moving inwards and outwards. Shift the platter just a little and check again. The distance (d) should be the same all time. Be patient and take your time. You will certainly succeed in the end. If you are really certain that you have attained the best position of the platter on the spindle, you can gently turn the crews. Do not tighten the first one too much, but give all three the same treatment until you have tightened them well. And then check again of course.
	IDLER WHEEL This drawing is from the original manual of the TD 124 Mk2 and tells you how the adjustments of the idler wheel should be made. If your TD124 works perfectly well and you see to it that the adjustments are right, than there is obviously no need to make changes. The well functioning also depends on other adjustments and the cleaning of some rotating parts.
	CLEAN The speed selector has idle positions in between the speeds. If you do not play, always set the selector in between two speed markings. In this way the idler wheel will not touch the stepped pulley and will not risk to loose a perfect round shape. Clean the periphery (edge) of the wheel with cotton wool and blue methylated spirit.

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The Spindle and Bearing Housing

	PRECISION BEARING The platter of the TD-124 fits directly on the flange on the top of the spindle and is secured by three screws. The shaft (spindle) is turned and polished to the highest degree of precision.
	IRON AND ALUMINUM PLATTERS The aluminum platter does not have the same shape in the center. It needs an intermediate disc to fill up the original space between flange and platter. The intermediate disc is secured by the three original, large screws. The platter is fixed to this intermediate disc with three smaller screws.
	TEFLON AND SINTER BRONZE This is a drawing to portray the design of the heavy main bearing and shaft without which the turntable does not have the high end quality. The precision turned spindle is polished to the n-th degree and fits with a low tolerance in the 2 sinter bronze sleeves. If the bearing needs maintenance, it should be cleaned with oil. The earliest TD124 turntables had Teflon sleeve bearings (instead of the sinter bronze bushings) and needed to be cleaned with methylated spirit (blue alcohol) if cleaning was necessary. The recommended oil. If the Caltex or Texaco Regal Oil B (as used for hydraulic power transmissions) as indicated in the manual is not available, use a non oxidizing, non sticking, high grade light mineral oil (SAE 20).
	BEARING HOUSING If the bearing and the shaft are not handled well, the specifications will not be met. It is of the utmost importance that the housing is hermetically closed at the bottom so that the oil can not leak and the spindle hangs as it were in the oil bath so it is perfectly centered and will turn evenly.
	BALL BEARING The ball was kept in place by a circlip (a washer which is a ring of thin, flexible metal) which clamps into the cavity at the bottom of the shaft. This cavity was greased with dark reddish bearing grease. That was the case with the second hand TD-124 (Mk 1) which I bought in 1978. Later models I bought did not have this grease bearing.
	HERMETICALLY SEALED HOUSING If the oil can leak, the spindle is not supported evenly by the oil and cannot do its job properly. The bearing housing has a base plate at the bottom which must be screwed tightly. In between the housing and the base plate (spindle support pad) a gasket takes care of the complete fitting of the base plate without any leakage. In the drawing it is the thin layer which protrudes at the sides. The original gasket is of a thin material with a brown color. It is a delicate fabric and breaks easily. This gasket can easily be replaced by a gasket that you can cut out of a not too thin but at the same time rather soft transparent sleeve for protection of record covers. You also can use the same sort of transparent plastic, the kind table covers/cloths are made of. This gasket should be larger in diameter than the base plate so that you can trim it to size once the base plate has been screwed on the housing/chamber. When in 1980 a friend and I were developing a turntable with a heavy platter, we initially used TD 124 bearings and spindles. We were thinking of making more tables than just two. So we asked a factory what the price of these parts would be. Recently I found the measurements he wrote down when measuring the parts during our initial conversation. You can see them here.
The bearing shown above was made by an expert technician from Huntington Beach, California, who sold specific items for the TD124 in the past.	MAINTENANCE AND REPLACEMENT Maintenance is important. Clean the bearing and the shaft with oil. Cut a new circular gasket out of plastic sheet. Put it on the bottom of the still empty housing and with the end of a pair of scissors you make the three holes. Just a small hole will suffice and work better than a large hole. Now put the original, gray, plastic bearing plate (which supports the ball) in the housing. Then put on the plastic gasket with the holes right on the spots were the screws will be inserted. Put the base plate on and insert the 3 screws. Fasten the screws carefully and fasten them tightly. Replace the housing in the chassis of the TD124. Fill it with oil for about 1/3 and gently place the spindle (the platter attached to it) in the shaft and let it slowly settle by itself. Do not force the spindle to go down. The spindle cannot be exchanged for a new one without going to great expense. But if the bearing housing does not support the spindle as it should, if there is some play, it is less costly to have a new bearing housing or sinter bronze bushings made.

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The Motor and The Suspension

	MOTOR This is what the original motor looks like. This motor was taken of an old machine which could not be restored. One of the shafts for the suspension was broken and the aluminum plate (mounted between pulley and motor) is missing too. A short time after the introduction of the Acoustic Research turntable with the floating (suspended) chassis, designed by Mitch Cotter, Thorens introduced their version of the belt drive turntable with the floating subchassis and named it TD 150 (from which Linn developed their LP12, also inspired when they manufactured the parts for the Ariston sub chassis player). The TD 150 was introduced in 1966. In that same year however, the TD-124 Mk2 was launched but manufactured only for a few years and was eventually replaced by the TD 125 which was produced already from 1968 on.
	PABST AUSSENLAUFER For several years the factory had enough spare parts for the TD124 in stock for replacement and servicing. Despite its sturdy built, the motor of the TD124 could have worn out if the machine was ill treated or accidentally damaged. In 1977 the factory ran out of motors and a new motor was designed especially for the TD124 by the renown manufacturer Papst. This motor was a so called "Aussenlaufer" with the advantage of the flywheel effect. (A similar type was used in the early Acoustical 3000 belt drive turntable, but then with a large capacitor to start the light platter instantly.) While the suspension of the original motor needed 3 grommets, this new Papst motor has longer shafts for the suspension and needs 6 grommets which should be arranged as the image on the left indicates. This should result in a better way to minimize the transmission of vibrations from this motor to the chassis. (Image taken from the original Thorens document.)
	DECOUPLING This picture shows how the rubber isolation rings should be placed in order to attain a maximum isolation. From bottom to top: Hartpapier-Scheibe (hard paper ring), Gummitülle (rubber ring which is inserted in the chassis), Gummitülle (rubber ring), Hartpapierscheibe (hard paper ring), Sprengring (locking ring). Because of the different electrical parameters a new connection diagram was supplied.
	TWO KITS It is possible that you may come across such a fairly new motor. Two different motors were manufactured: kit 3805-200 for 200-240 Volts/50 Hz. and kit 3806-110 for 100-125 Volts/60 Hz. Thorens gave instructions how to take out the old motor and replace the new one, inclusive of a new wiring diagram. At left the replacement motor that I photographed for Joachim Bung's Book on the TD-124.
	CONNECTIONS This is the circuit diagram showing how to connect the two different Papst Aussenlaufer motors. The 220 Volt/50 Hz. motor has a capacitor of 0.47 uF/630 Volt plus a resistor with a value in the range of 33 - 82k, 1/2 Watt. The 110 Volt/60 Hz. motor needs a capacitor of 1.5 uF/250 Volt and a resistor with a value in the range 10k - 33k, 1/2 Watt. Legend: SW = switch, Blau = blue, Gelb = yellow, Rot = red, Grün = green, Kondensator = capacitor, Widerstand = resistor. Steve Clarke from The Analog Department was curious about the workings of the Papst motor and built it into the TD-124. He gave a thorough evaluation of the electrical, mechanical and audio related aspects. Though the TD-124 remains an idler wheel turntable, it shows that every aspect of a design contributes to the audible results. Steve noticed a significant difference in sound with the Papst Aussenlaufer motor. This does not necessarily mean that the new motor is in itself a bad design. It means that it should be implemented in a different way or just not in the TD-124. An idler wheel drive is not the same as any idler wheel drive. That is why a Garrard 301, a 401 or a Garrard 4HF do perform in a different way than a Thorens 124, 135, or 111, etc. does. And also a Lenco with the variable speed and pitch adjustment has a different sound. Much of the differences not only depend on the design of the turntable, but also on how their function is optimized in the total system. It is reported that the Pabst Aussenlaufer behaves differently if compared to the original TD-124 motor and the original is to be preferred. The old motor can be serviced. Check the internet for a kit. Or check this page even if you do not read Japanese.
	MUSHROOMS With four insulators shaped like mushrooms, the chassis can be de-coupled mechanically from the plinth. Here you see the original rubber mushrooms. Visitors of this page often ask me if new ones are available and where to get these. Browse the www or check eBay.
	IMPROVISATION You can of course manufacture some insulators yourself from pieces of rubber tube and top these with small rubber discs and glue these together. Some people just let the chassis rest on the wooden base as I do. But then it is important that the audio rack or cabinet is well de-coupled from its environment by means of spikes or similar gadgets. The turntable has to be level at all times. The horizontal position of the chassis can easily be adjusted by turning the wheels on the threaded bars.
	HORIZONTAL ADJUSTMENT The suspension system of the TD 124 is in essence a simple system, but ingeniously designed. The chassis has threaded holes in which the threaded bars can be screwed. Discs have also threaded holes and can be turned to obtain the best position. By turning the discs clockwise the distance between chassis and plinth is increased. These discs rest on top of the mushrooms. In order to not damage the top of the mushrooms, intermediate rings have to be placed on top of the mushrooms.

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The Platters and The Clutch

	SIX PADS The main platter has 6 small rubber pads. These are there to support the aluminum top/sub platter in the playing mode. That is when the aluminum top/sub platter is lowered by disconnecting the clutch from it.
	LIGHT ALUMINUM PLATTER It is possible that the clutch does not work correctly. Maybe the aluminum platter is somewhat round on top, overall, or just partially. In that case it will touch the clutch in the up and in the down position. Or the platter may be slightly concave. If it is extremely concave it may be free from the clutch at all times. Either situation has to be corrected. Put the aluminum sub platter on a glass plate and check if the rim is perfect and its edge is supported perfectly well, all around. Even though it is, it is possible that some changes in the surface can be detected. You can check this better if you unscrew the center 45 RPM adapter. (If you are dismantling this center piece, do note exactly what you have done. This makes it easier to reassemble it.) By taking off the mat you can check the surface better. There should not be any part of the aluminum platter that is lower. If the platter's rim and surface needs correction, you should only make changes if you are really sure that you can do that, and if you are certain that the aluminum top platter is the culprit of the malfunctioning of the clutch system.
	THE WORKING OF THE CLUTCH The clutch has the shape of half of a circle. It is a strip which should not have a bend. Check if the clutch is bent or torted. If it is, flatten it. The clutch can of course be adjusted. The drawing (below) shows the functioning of the device. For better understanding you can save the drawing and view it in detail when necessary. There are three screws with a specific shape. If one or two are missing try to find the same or similar ones with the same diameter and thread. Have one end turned by a machinist exactly to the shape of the original screws. In the playing mode, the holes of the clutch fall over the top end of the screws. That means that the clutch is in the down position. By moving the knob of the clutch away from you, the clutch will be lifted and will rest on top of the screws. This means that the aluminum sub platter is resting on the clutch and is lifted also, just enough to let the main platter turn freely underneath, without constraint. If the platter is not turning freely, the locking nuts have to be turned loose and one or more bolts have to be turned as to protrude more. This adjustment is rather delicate. And you only have to make the adjustment if the strip is not bend and only if the former owner has adjusted the bolts unwisely. When playing a record, the sub platter should never touch the clutch.

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