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.
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 a slight bend to 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).
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 not reason that one of these could not be kept in operating condition, with routine maintenance at intervals, indefinitely. Other words, it can outlive it's owners. Actually, this 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.
Installing the electrical parts while replacing the old neon bulb resistor with a new one and replacing the old .01 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.
Notes on the motor: it runs strong and about as cool as I've had an E50 run for me. A very nice sample. All this motor really needed was normal maintenance (clean all parts, new bushings, clean felts, a new thrust pad and a new thrust ball, some fresh lube) and some TLC to put it together right. These later models did come with a stronger motor than did the early units.
next: clutch maintenance, we have new pads to install.
Just a very light touch of lapping to flatten the little high spots around this surface -- which must interface with the top of the platter bearing. By the way did I mention that when you screw the platter down onto its bearing, it does not run 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 mic 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.
The Light Aluminum Upper Platter
It needs some straightening.
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.
The TP14 Tonearm
Repair Parts lists:
Main Platter Bearing Parts:
Labor: Flat Rate @ $400 per project.
Total invoice at this point:
*Hardness Rockwell C-scale
Assemble - Adjust
Test - 30 hr run-in
Motor tear down - inspect - reassemble - test - finish
Inspection / Evaluation:
Disassembly / Inspection
Course of corrections and upgrades
Assemble / Adjust / Test
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