Thorens TD124 sn 33389 (late first version)
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.
Inspection; mechanical and metrology
Idler wheel and associated components:
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.
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 Ø .1966. The bushing bore in the chassis measures from Ø.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.
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.
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.
Rotor shaft measures: range: .1868" to .1869"
cleaning cycle re: the rotor bushings:
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"
Parts from The Analog Dept: Torlon brg thrust pad. (main platter brg)
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:
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:
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.
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.
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.
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.
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.
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.
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:
All that is left is for me to provide a suitable foam-filled ship carton.