Project SN 59805; A Thorens TD124 mkII in for refurbishment
movie #1: upper platter runout (Quicktime or Windows Media Player)
Disassemble - Inspection - measure / Evaluation
Left two photos. The "suppressor cap" capacitor has failed. Evidenced by the leaking material oozing from it. This capacitor is designed to prevent the speakers from making a popping noise when the motor is turned on and off.
The idler wheel carrier appears in acceptable condition. The bushing / shaft assemblage, that allows vertical travel to this assembly, was stiff in its action upon reception. After looking this over closely I determined that its stiffness was due to the absence of lubrication. The original lube had long since evaporated and dried out. The solution was to apply the recommended (by Thorens) 20 wt. turbine oil to the bushing and shaft area repeatedly (several times) to ensure that the bushing and shaft were well saturated in lube. After wiping away the excess lube vertical travel action had become smooth yet absent of any excessive horizontal slop. Lube was also applied to the areas of this assembly that have a hinge action.
Also of note is that the axle pin that fits the idler wheel has installed to its base area a thrust washer and also a spacer washer. The thrust washer is a transparent nylon ring that fits very snugly over the axle so that it remains fixed in its position while the idler wheel spins over it. The spacer washer (brown phenolic) is intended to fit beneath the thrust washer and is used to adjust vertical position relative to the stepped pulley with which the idler wheel makes contact.
Here's a photo of the cleaned parts assembled and ready for use:
Note that the transparent nylon washer is to carry the thrust of the idler wheel. The brown phenolic washer beneath it is to adjust vertical position of the idler wheel. This position of the phenolic spacer is optional.
Stepped Pulley and Axle:
Measuring diameter of the axle of the stepped pulley to check for any evidence of wear.
Results of measurements:
Axle diameter: .1573 inches. Using a 0-1 inch micrometer this measurement was taken in a circular array at several positions to check for roundness (a personal habit of mine) and I saw no variations greater than .0001 inches (that is one / 10-thousandths of an inch). This really reflects the quality of mfr. from the factory. But it also checks for any unusual evidence of wear. Additionally, the stepped pulley axle shaft shows no visual evidence of wear.
Chassis, Hub and Bushing Bores:
Using the Mahr bore gage I checked the upper and lower bushings within the hub to check for evidence of wear, taper and out-of-roundness. All of the areas checked indicated a diameter of .1581 inches. Upper and lower and with no deviation seen in roundness.
Subtracting the axle diameter from the bushing bore size and you get a running clearance of .0008 inches. (that is eight ten-thousandths of an inch). I take this as nominal and within a working tolerance of size that would have been acceptable at the Thorens factory the day it was made. Good news! The stepped idler axle shaft and the hub bushing bores check nominal and acceptable!
Stepped pulley axle thrust bushing:
Below: two more detail photos of the thrust pad.
left: stepped pulley axle thrust pad with its unused side up. On this side I notice a horizontal scratch, but, fortunately, this does not intersect with the thrust point. We can use this side in the refurbishment.
However, the flashing (burrs) seen on the perimeter of this pad will be trimmed off to ensure a more central fit within the inside diameter of the hub where it assembles to.
Of note is that this pad evidently does not withstand a heavy vertical load when in use. It is the bushings and the axle that take the much larger load-force in the horizontal.
Cleaned, lubed and ready for further assembly, the eddy brake speed adjuster ring. Beneath the ring is a heavy felt donut, soaked in fresh 20 wt. lube. This assembly is held in place with a large C-clip.
hint: click on thumbnail to view image full size. Note again the position of the thrust washer and the phenolic spacer beneath it on this idler carrier assembly. Ready to accept the idler wheel in case we choose to use the spacer, otherwise the spacer goes up topside between the keeper ring and the idler wheel hubface.
With the idler wheel retainer ring fixed above the wheel. Note that there needs to exist some clearance between the wheel and this retainer, otherwise it could become a source of unwanted drag. (important!)
Idler wheel rubber and its condition:
Condition of the rubber: No evidence of age cracking or crazing. Rubber appears supple and soft to the touch. Initially it looks like a very good specimen to me. However it will be given further evaluation when the drive train is assembled intact and being tested. And what I've learned after playing several records is that this wheel does, unfortunately, have a flat spot. It's a soft thump, thump, thump kind of situation. It will need to be repaired or replaced. As a thrifty solution we have found that Terry Witt, at Terry's Rubber Rollers can re-rubber this wheel for $35 usd plus ship. The wheel is off to Terry as of 6/10/2019. Meanwhile, I have one of my spare idler wheels installed to 59805 for performance evaluations.
see page bottom for results of the recovered idler wheel as received from Terry's Rubber Rollers.
Steel Ribbon CB771, its link CB814, and the Speed Change Cam CB906, and the speed change drum CB776
The lube within the bore of the speed change cam had partially evaporated, causing this component to be very sticky against the post axle about which it rotates. Actually, the cam did not want to pull free of the post at all. Of course the C-clip needs to be removed, then the cam should lift up over its axle post freely. This one did not! But it did eventually pull up off its post. After cleaning with lacquer thinner to both the bore of the cam and the OD of the post, inspection revealed no evidence of wear or damage. So fresh automotive wheel bearing grease was applied into the bore of the cam as well as onto the axle post. Upon reassembly the cam now rotates smoothly.
The steel ribbon showed evidence of having been removed previously. Two clues were evidence of this. Clue #1) The screw that normally is used to anchor the speed change ribbon to the speed change drum was found on the link that joins the steel ribbon together into a loop, and one of the screws normally used on the link was found holding the ribbon to the drum. No problem here as the machine screw thread size is the same for these three screws. The difference is in screw head configuration. The link screws have a larger head diameter than does the drum screw. It would have worked as it was but now all three screws are in their correct assigned locations.
Clue #2) there was (and is) a slight bend to the ribbon; a minor fold on the slack side of the ribbon.
Apart from the mild bend, The ribbon appears undamaged, which is good. It will operate normally. It is noteworthy to mention that It is easily possible to partially tear, break and bend this steel ribbon when mishandled. Usually this will happen while trying to disassemble or when trying to assemble and adjust. The trick to success with this part is to have a bladed screw driver that has a very close fit to the slot of the screws. This way the screws stay on the blade during assembly and the blade does not 'cam out' while tightening and loosening. I see lots of evidence to support this observation. As to the screws on this particular assembly, there is some minor evidence of miss-handling (cam-out burrs), but not nearly as bad as I have seen over the past several years. The evidence tells me that care was taken, yet this particular component truly has a learning curve to climb for those who would work on these players.
By the way, when assembling the the ribbon to the cam and drum, orient the parts as shown in this photo (to the left) and the speed change lever needs to be set to the 78 rpm selection. (and the cam follower is on the 78 rpm level of the cam)
More wheel bearing grease was applied to the shaft of the speed change drum and also within the nylon bushing through which if fits. I have found that using wheel bearing grease on these particular components results in the smoothest action felt at the speed change knob. Please note that Disc Brake wheel bearing grease is used here and no where else! On the parts that spin we use the Thorens ROB oil (modern equivalent which is a 20 wt. turbine oil).
Speed pitch adjust:
Main Platter Bearing:
Left: The original bottom thrust cap, gasket and Nylatron thrust pad. These thrust caps and pads are by design somewhat flexy and do allow the force of gravity, combined with the weight of the platter assembly, to permanently deform both cap and pad. However it is possible to minimize this by the methods we handle these players. More on that later.
Left: Looking at the bottom end housing with old bushing prominent. Notice threaded hole at 2 o-clock with a red arrow pointing at it. There is evidence of partial thread damage. This is not enough damage to affect fit and function of the threaded hole, but it is evidence of a false start.
This reveals that the shaft/bore spinning clearance has worn slightly oversize. (normal wear/tear) I work for .0006 - .0008 (inches) shaft to bushing wall. We'll install some fresh bushings from Oilite. Additionally we'll need a new bottom-plate gasket and thrust-pad. And that shaft could use a light polish.
Left: 100x microscope detail view of the old bearing thrust ball. Note that this view is of a very small area of the actual ball. There are several such wear spots to be seen on this particular bearing ball.
Left: Platter Bearing shaft after polish with a very light/fine compound. Shaft diameter measured after polish reads Ø .5501 inches at both upper and lower bushing contact areas. Roundness was not affected.
Left: Looking at shaft end after clean and polish but also if you look closely at the bottom end of the shaft the bottom face, in particular around the OD chamfer has been lightly lapped to remove a sharp tight burr that was left by the factory that made this part.
Notes on the bearing: The old bushings might have been retained but they did show some evidence of wear. The new bushings have tightened up the operating clearance between shaft and bushing wall while retaining a free state spin. Fresh delrin thrust pad, Fresh bearing ball, Fresh gasket. Standard maintenance. Of course the cool thing about this is that the TD124 is built to receive maintenance. There is no reason that one of these could not be kept in operating condition, with routine maintenance at intervals, indefinitely. For multiple generations. Other words, it can outlive it's owners. Actually, this idea really seems to be the case. Many TD124's in service right now have already out-lived their original owners.
Left: motor with its wire harness, the voltage commutator, its cover, mounting isolation grommets, phenolic spacers and c-clips. That one phenolic spacer (to the right) was attempting to escape, but was captured and did not get away after all.
Condition of the grommets; going soft with age and would soon disintegrate if left in service. We'll replace these with some fresh ones.
Checking the motor coils for evidence of damage. To do this I use a Fluke multimeter to check ohms level on each of the three circuits within each coil and then compare readings of these between Coil #1 and Coil #2. We are looking for similar readings at each circuit. Here are the results:
This indicates that the wires are undamaged (not burnt or broken) or otherwise we'd see a much larger variation in the ohms read between a healthy working circuit and one that has damage.
Great. We can move forward with the coils in this motor.
Looking into the motor.......
Left: A100x microscope photo of the Ø2mm thrust ball used at bottom of the rotor shaft. Like the main platter bearing thrust ball, we see strong evidence of the mfr tooling method in producing these parts. To be replaced.
The Rotor and Shaft
Measuring the rotor shaft for form and size.
Short end: Ø .18660 to .18670 The taper variation seen is due to slight wear. Checking for roundness indicates zero deviations.
Long end: Ø .18695 to .18685 The variation seen is due to slight wear. Btw, these measurements I resolve to the nearest 10-thousandth of an inch. .0001 inches. (While the instrument reads out to 5 decimal places.)
Differences in size between long end and short end, I attribute to manufacturer's process variation. Manufacturers work to within a tolerance specified within their process controll. And now we can see an average difference between the long and and the short end of .0003 inches. That does not surprise me (coming from the manufacturing world myself)
Visually we can see the areas where shaft and bushing walls were in contact.
re: instrument calibrations. The outside micrometer has its calibration set to zero (anvil closed), 1/2 inch and 1 inch readings are calibrated using a set of inspection grade gage blocks I have on site. Since this instrument reads out to 5 decimal places, extreme care is given to surface cleanliness of the instrument.
Micrometer: Mitutoyo No. 293-676 digital, reads inches or mm. Living in the United States my first preference is to work in inches. Even though this Swiss turntable was built using the metric system. Did you notice how close in size the rotor shaft is to the fraction 3/16"? 3/16" in decimal is .1875". Our shaft is measuring .1866 to .1869 inches. Close enough to call that rotor shaft 3/16 inch..... me thinks....
Above and below: looking at the motor with the bushings upper and lower removed, cleaned.
Above: After a bath in lacquer thinner, the bushings are checked for cleanliness then the bores are measured using the Mahr bore gage.
In this instance a set ring in use has as its diameter .1869 inches. The set ring is used to calibrate the Mahr gage to read zero at .1869 inches. Then reads are taken within the bushing bores and the difference in read between the bushing bores and set ring determine actual bushing ID size.
One bushing measured .1876 and the other .1877 inches in diameter. Both checked round with zero deviation seen. Same for taper. No taper and no out of roundness on the bushings. This is better than it thought it might be when I first looked at the bushings when taken apart. While in the motor, the upper bushing had apparently been running dry. The lower bushing showed some evidence of lube. But measurements tell me that we have a running clearance of shaft to bushings of.0008 one end and .0009 other end. We'll compare that to the new bushings from Audiosilente, next......
New motor bushings from Audiosilente:
Above 4 photos: the new bushings from Audiosilente
Above photo: Checking the new Audiosilente bushings for bore size and form.
Both of the new bushing's inside diameters measure very close to the same in size at Ø .18720 inches. There was no taper or out-of-roundness detected while measuring the bore with the Mahr Gage pictured.
The rotor shaft diameters measured between Ø.18660 to .18695. With this information we can determine that the bushing to shaft operating clearance will be between .0006 to .0003. That is quite a bit tighter than what was measured between the old bushings and shaft ( .0008 to .0009 inches clearance)
Another area of focus is on the bottom radius at the spherical end. This radius fits to the spherical seat found within the motor bottom cover. It is imperative that these two features work together (bushing sphere and casing sphere) free and smooth to allow a self-aligning action to take place when the motor is assembled.
And how the bearing fits into it. Two spherical surfaces that are designed to swivel enough to allow the bushings at either end align closely to the shaft that goes through them and, ultimately, result in a fit that allows the rotor shaft to spin on a cushion of oil without making contact with bushing walls...That is the goal.
Of note is the reduced bushing/shaft operating clearance. Reduced from .0009" down to .0006". The shaft/bushing alignment process, for me has evolved. On my first motor (chassis #2729) I had found a method on a Japanese website. This is circa 2005/6. That process involved getting the turntable chassis and motor assembled so that we could adjust shaft/bushing alignment by shifting position of the upper and lower casing halves relative to one another. Using my holding jig that secures a chassis onto a platform with legs. By making tiny adjustment while the motor hung from its grommets within the chassis, and then listening with a mechanics stethoscope at the running motor checking to hear if the last adjustment resulted in lesser or greater noise being heard.
Then, about three projects later, I changed the process method to make this adjustment with the motor out of the chassis and while holding it in my hands. Not wired up, no power!. By shifting position of the case halves with my fingers and a very small mallet, or a small block of wood. Playing with the individual bolt tensions holding the case halves together to make smaller and hopefully more precise adjustments...Meanwhile, and all the while, I'm checking progress by spinning the rotor shaft from its top end by thumb and forefinger. And I'm looking for the longest spin down time as evidence of the best alignment. For me this method results in freer spinning motors than does the previous noted method.
About the lube in the motor. Because the factory indicated 20wt turbine oil and a specific type of Texaco oil it is possible to get a modern day equivalent. And it is already widely known that the 20 wt Electric Motor Lube under the Three-In-One brand name comes very close to to this Thorens factory spec as noted in the service manual. Many individual owners around the web have suggested the various different lubes they have used in their E50 motors. However I have read no one claiming 'Eureka, I've found it!' about some great new oil they've tried. Not yet, anyway. So it's 20 wt Turbine Oil.
After running the motor for a good 30 hours, and then taking it apart for a, check, clean, reassemble, adjust, I found no evidence of premature wear. I did notice that the upper bushing was not as wet with oil as I'd like it to be. You can put thicker felts inside the swivel joint bracket, but gravity pulls the lube down and out through the bottom of that upper bushing. I've seen this on every other E50 I've had apart. For myself I'm going to remember to periodically remove the drive pulley and put several drops of 20 wt into that top bushing. Just trickle it in around the shaft. Like every time you check the belt, perhaps more often.
From a cold start I have a 'playable' operating speed within the first rev --within a percent of 33-1/3rd. Then as the player warms up the strobe window bears witness to a very steady pace. And it will hold that throughout an all-day session. Or during the day when you turn the turntable back on after an hour's rest or so you'll see the speed lock into 33-1/3rd within that first rev. To sum, it runs strong and about as cool as I've had an E50 run for me. A very nice sample.
Installing the electrical parts while replacing the old neon bulb resistor with a new one and replacing the old .01uF pop capacitor, (that had suffered a melt down) with a new one and of a type that won't puke all over the place should it fail.
Cam follower/switch actuator assembly. It has been cleaned in solvent to melt away the old lube. Next it was soaked in fresh 20 wt. turbine oil at two places; the cam follower (roller) and also the spring controlled push rod that actuates the on/off switch. The hub that goes over the post axle receives fresh wheel bearing grease. It is held in place over the axle post with a phenolic washer and C-clip.
next: Clutch, Upper Platter maintenance and Trouble Shooting: we have new clutch pads to install but there is a lack of clearance between two main components at a critical location.
By the way did I mention that when you screw the platter down onto its bearing, it does not spin concentric to the axis of the bearing! Nope, one must use a dial indicator to "dial in" the platter to bearing axis. I'll add a video of that process before this unit leaves the premises.
Left: Using a depth micrometer to find a precise depth measurement in this hub relief area. (.202 inches) (then add .04 inches - thickness of friction disk total = .242 inches) The bottom surface of the upper platter hub must fit within this area and have a running clearance...but there was interference instead of clearance between the two surfaces!
This one measures .261 inches deep. That is a difference of .060 inches between the iron platter and the zinc one. And the shallow (zinc) platter is the one that won't fit either upper platter from This TD124 or the upper platter from the TD124 on my personal rig. It looks like a manufacturer's defect. An error in a machined dimension on the platter.
Next, I'll check the area in question on the light upper platter for a height dimension to confirm what I already think.
For this check I'll use a machinist's surface plate and a height gage with dial indicator. The upper platter is placed mat down, flatly on the clean machinist surface plate. Then we do the following;
Read the vernier. This is the older style height gage with vernier. Finest read possible on this gage is .001 inches (or .025 mm). So the process is that with the indicator on the height gage zeroed on one surface, read the vernier, then write that number down so you don't forget it. Then adjust elevation of the indicator so that it reads zero on the second surface. Check the read on the vernier. The difference between the one read from the other reports the vertical distance between the two surfaces.
In this case the read was .258 inches. Well that explains it. The hub on the upper platter was definitely bottoming out on the shallow relief area of the zinc platter.
This one is working at the moment. The friction pads on the zinc platter have a thickness of 1mm. (.04 inches) I'm replacing those with these cork/rubber pads that have a thickness of .062 inches. That raises the light upper platter by the difference. (.062 - .04 = .022) and should have a running clearance of .006 inches.
And... now the hub does not touch anything within that relief area on the zinc platter.
But what about the clutch pads? Will they work? Firstly I'll need to straighten this particular light upper platter because it came to me with some subtle bends.... And also there is some evidence of it having been worked. Hopefully, the previous metal work has not stretched and worked the soft aluminum too much. That comes next.
After sorting out the clearance issues with the heavy platter beneath it, it was determined that the light upper platter still needed some straightening. A little bit of careful nudging, using some custom forms, clamps, and a heavy tempered glass plate result in an upper platter that offers 95% error free clutch action. A great improvement over the condition it was received in.
The TP14 Tonearm
Left: The TP14 in the foreground with a functional TD124 mkII in the background. By this moment the issues with the bent upper platter have been resolved. See above documentation for cause and correction. The upper platter is still not perfectly straight, nor will it ever be. But, with the largest issue of the upper platter hub face bottoming out within the relief area of the zinc main platter compensated for by using thicker friction pads to carry the upper platter high enough to clear, we manage to have enough working tolerance of dimension to get a functional clutch operation. By this time I've been listening to #59805 while within my heavy slate plinth and using the BW tonearm with Sonus Blue cartridge. I like the presentation on this player.
This arrived in a non-functioning condition. I found that the tonearm would not lower the cartridge down onto the record. However, now I understand that there is a close adjustment requirement at 5 areas of the fussy little tonearm. Fortunately the TP14 Instruction Manual does teach how to correctly set this arm up. When set up correctly the stylus end of the arm has a total range of a bit over 1/2" of vertical travel. And this requires 5 individual adjustments to carry out..... in a particular order.
Here is a close-up look at the pivot cone on the inboard side. Look closely at the full sized photo to identify evidence of bearing wear -- with indentations from bearing balls plainly seen worn into the steel cone.
Here's another close-up look at the opposite pivot cone. On this side we see evidence of damage to the cone at it's sharp tip, but we don't see any bearing ball indentations here as are to be seen on the other side.
Mounted to the TP50 headshell is a vintage Shure M91E moving magnet cartridge. The kind that is carried in a steel clip. The photos indicate that this cartridge has been in place for several decades. Weathering has covered the metal parts with a coating of oxidization. We also see that the cartridge clip wires have been soldered to the connector pins of the TP50 headshell. This is and has been a common practice from back in the day when all this was new.
We have a new EVG stylus assembly to go with the Shure M91E.
Prior to putting this new stylus to work, let's have a look at the diamond to see if it is indeed new.
Left: close-up detail of the Thorens tonearm cable...from the factory splice connection at the base of the tonearm are the wires going out to the phono stage. This photo indicates preparation prior to the fitting new upgraded Nutrik Gold Plated RCA plugs. This cable, actually, is a pretty good grade as is evidenced by the cables used in all other Thorens tonearms I have seen.
Now, with the tonearm internal wiring partially exposed, is a good time to run continuity checks at each wire as well as for capacitance.
Tonearm internal wiring:
6/3/2019 -- Continuity checks using a multi-tester indicated a lack of continuity on the right channel ground wire. (green) Interestingly, this appears to be an intermittent loss of continuity sometimes checking ok, other times not. At this point there have been two occasions when I have thought I had made a successful repair, with continuity checking good prior to assembly, but then after assembling and adjusting the tonearm, continuity fails on the right channel ground. In the meanwhile it checks ok on the other three wires. .
The blue, black, and red wires pass continuity. It is the green wire that lacks it. Visually, along the entire exposed length of these wires, I see no evidence of a break.
6/4/2019 -- And then, after letting this assembled arm sit for a day I performed another continuity test and all wires checked OK!
At this point I have the arm on the chassis, adjusted and playing records. No ground issues. See photo at top of page. In fact sound quality seems quite good. I'll play this for several days to see if both channels continue working. And I have no explanation for the intermittent loss of continuity to that green wire. Today both channels report very well.
Fwiw it takes some effort to set one of these arms up. As noted above there are 5 points of adjustment just to set the 'working zone' of that cue lift apparatus. Adjustments to be made at "y" and "L", "P" and "N". (Figure 4) And let's not forget "U" in Figure 3. (Thorens TP14 Instruction Manual)
With the Cue linkage hooked up, the arm has something like a maximum of 1/2 inch of vertical travel. Want to adjust vta...?...you'll need to readjust the cue up or down to compensate for the change you just made. Want to pull the arm off the chassis...? You'll need to pull (with fingers) the link "C" out of its joint at "D". Then be careful about "T", it just barely clears that frame gusset in the middle of the chassis armboard area. You kind of have to hook it under the gusset each time. There is room for this, just barely. (Those creative engineers at Thorens back in the early sixties...) See Figures 2, 3 and 4 in the TP14 Instruction Manual for an annotated drawing as a guide.
Left: Figure 1 shows the one and only overhang adjustment available on this tonearm. Thorens published nothing other than this note for setting overhang. They do not recommend Loefgren A or B, nor Stevenson alignments. Just this 49mm length from stylus point to the back edge of the headshell. So that's how I have done it. Although it was done precisely on a machinist's surface plate using angle blocks to hold the headshell square while using a height gage to measure this critical distance.
Below: Looking at the cartridge and headshell:
Well the tag wires and clips are still functional but really need replacement. Also, the soldering done at the 4 out-going TP50 pins could use some clean up.
By now the old wires have been taken off. Clip removed at cartridge end, desoldered from the headshell output pins. The old solder was cleaned off using a GC Braid wick to suck (most of) the old solder of the pins. Then the TP50 was given a lacquer thinner bath and another set of wires and clips installed:
Here's a demo movie of 59805 in operation (quicktime .mov file)
Movie #3: Demo (hint: click on the link)
Up to this point I have become increasingly impatient with this tonearm as I have wrestled with learning its assembly and adjustment complexities. But now, with the thing finally working predictably, I can listen to the damned thing. I can regard the simplicity and steadiness with which it handles while playing Lps. With all parameters in proper adjustment the tonearm handles intuitively and with a sense of confidence. Sound is better than I'd hoped.
About the M91E: It is held in
place by a steel clip that uses a fairly strong spring pressure to firmly clamp
the cartridge body at two points. By this method the cartridge can be
removed from the headshell via fingers and without turning a screw. The
thing that must be recognized, first and foremost, is that the clip can also
clamp the body incorrectly if it isn't understood where the grab points are on
this body. Well, now that I found these, I have a solid mount as well as
alignment geometries such as azimuth, offset angle and zenith angle that
are now in the ball park. And -now- it begins to sing for me. Now I have
detail, with clarity. It likely helped when I removed the old clips and
tag wires. That process caused me to focus on the M91E and notice that the
steel clip wasn't clamping the body correct, or squarely. My first
m91E with the clip!
It sings more properly now. Perhaps I'll look for one of those old vintage cartridges for my collection. Replacement stylus assemblies don't have to be expensive and are available. And credit must be given to the TP14 that carries it.
Test Record time: 6/9/2019
I wasn't surprised to see this arm/cartridge fail track 8 bias (torture) track. But it did pass the previous tracks 6 and 7. Side 2 tracks 2 and 3; arm/cartridge resonance reports a 9hz resonance. Hmmm. Effective tonearm mass is not published by Thorens. And.... we don't have a figure for cartridge compliance because they didn't report this on the product spec sheet..
But I have a test record reporting my arm/cart resonance happening at 9 hz.
It's possible to insert the two unknown values into the formula below* that will result in a 9 hz value.
Here's what I have:
arm eff mass:? -14g
cart wt: 5.6g
fast wt: .5g
compliance: ? -15
All I have to do is insert sensible values(14g effmass, comp = 15) into arm mass and cart compliance fields. and I get 9.16hz
It's a 14g effective mass arm. Lighter than you'd think just looking at it. But the build on this thing is light. The aluminum sheet metal work appears 1st rate.
* using the formula below (borrowed from the Moerch website) I can insert values that result in a 9 hz resonance.
rf = 159 / sqrt ((eff. mass + cart weight + fastener weight) * (compliance))
I'm tempted to make some listening comparisons between my 13943 and this 59805. Why not, the signal chain from the phono stage down ward will remain the same. We're just comparing a Shure M91E on a TP14 against a Graham 2.2 with Shelter 501-II and a Beyer Dynamic step up trannie thingie. So I did today. And you know that Shure M91E deserves some respect. Properly set up it definitely plays in the 'pretty good' category. It was near top of the heap back in the early seventies when this was current.
Idler wheel update 6/23/2019. The idler arrived back from Terry's Rubber Rollers today. Pretty quick turnaround..13 days in all which includes transit as well as production times.
Here are some photos of the re-covered wheel:
Upon receipt I installed the renewed wheel. I found it necessary (and expected) to make a slight adjustment in elevation of the stepped idler wheel to accommodate the new rubber. Visually, as this wheel now spins, it appears to have absolute accurate concentricity between the rubber outside diameter and its axis centerline running through the hub bushing. A necessity. In the vertical I can see some run-out of the flanks of the new rubber. This does not affect sound quality nor speed accuracy of the drive train.
Listening. Right away I notice a much quieter background noise through the speakers as I have the turntable running, stylus in the groove and the clutch holding the upper platter just above and free of the spinning flywheel beneath. This is a good way to check background noise on a TD124 btw, in case anyone wants to know. Listening to music this unit sounds as good as I've yet heard it.
Inspect - Evaluation
About the Dual Plinth: I will do no work on this cabinet because I feel it is completely inadequate for this application. The main objection I hold for it - is - that due to its method of the joinery that secures the top plate into its cabinetry, it has a tendency to rattle in sympathy with drive train vibrations coming off the TD124. We need a plinth that dampens vibrations, not one adds to the drive train vibes! Rejected