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Thorens TD-124 E50 motor rebuild

Q

Quadman74

New Member
I just started this project today, I am using a kit from Audio Silente along with his MK2 motor post upgrade. I have an early'ish MK1 ser# 179xx, yes it has the nylatron main bearing sleeves, Replacements coming as well.

Looking at my rotor (the part that rotates in the motor) I have a 3-4mm wide black stripe around apprx. 1/2 of the diameter of the rotor near the bottom of it. It is not a wear mark but appears more like a thin coating of something, maybe old dried oil? It width is pretty consistent so I don't think it is that. 70% isopropyl alcohol did not phase it, before I get more chemical aggressive does anyone know what this maybe. I don't think it should be there and I think I should remove it.
 

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My Mk 1 has similar markings. I assumed it was supposed to be there and moved on. I'm sure someone with more knowledge will know for sure.
 
knotscott said:
My Mk 1 has similar markings. I assumed it was supposed to be there and moved on. I'm sure someone with more knowledge will know for sure.
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Good to know, Thank you. Kevin on DIY thought it may be to balance the rotor. I also noted that there are two small black dots at the top of the rotor one at the beginning and one at the end of the lower markings. So I suspect you are correct. They will stay on my rotor too.
 
Completed motor rebuild yesterday. New felts, bushings, coils and 2mm ceramic bb plus MK2 conversion all parts for Audio Silente. Felts soaked in 3 in 1 electric motor oil for 36 hours. Alignment went pretty good and my digital tach show 1740 RPM, I ran the motor for 10 hours last night. Motor temps seem high to me, with a DMM and a temp probe I was seeing 58C, 138-140F. This is in a wide open stand for easy motor access. That seems about 20-25 F above normal range. My RPM's are god and seem to indicate good alignment. Any ideas why my motor temps may be so high? When I ran the motor for 6 hours before the rebuild it got very warm but no where near as hot as last night. I also rewired the entire table, mostly with 20ga mil spec teflon with silver plated copper wire. New 33K resistor and new .01uF cap.
 
The new coils are heavier duty than the originals, aren't they?
If so, that might be why the motor is warmer.
 
Yes the wire windings are a larger gauge and physically the coils are larger than the OEM's. Resistance is lower too in the windings. I have read a lot of accounts where the coil upgrade lowered temps a bit not raised them. Today it seems a bit cooler generally seeing 131-132F in most locations with the small probe but I can still find areas that go to 140. I played a bit more with alignment today and it sure does not take much to see RPM's fall almost 100 RPM. I got it back to 1740, it is the quietest position. Hopefully as it runs in temps will slowly come down. I will not let it run when I am sleeping just in case.
 
Since no one answered your question, I believe the markings are likely from when they balanced the rotor at the factory.
 
So I rebuilt my motor as described above got the RPM's to 1740 and let it burn in for 6 days, but I'd run the motor 12-15 hours per day, off at night back on next day. So cycles of hot and cool. Today I took the motor apart to clean and relube and reassemble according to best practices I have read on various threads. What surprised me was the top felt pads were almost completely dry. I had soaked the top as well as the bottom felts in 3 in 1 oil for almost 48 hours, they were very wet with oil when I first assembled the motor. All I can think of is the new Audio Silente sintered bronze bushing on top was still thirsty and with the heating and cooling cycles the top bushing pulled the oil from the top felts. The bottom felts where wet as one would expect.

BlackScholes said:
I believe the markings are likely from when they balanced the rotor at the factory.
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Thank you, That makes sense. I left them as is.
 
Quadman74 said:
So I rebuilt my motor as described above got the RPM's to 1740 and let it burn in for 6 days, but I'd run the motor 12-15 hours per day, off at night back on next day. So cycles of hot and cool. Today I took the motor apart to clean and relube and reassemble according to best practices I have read on various threads. What surprised me was the top felt pads were almost completely dry. I had soaked the top as well as the bottom felts in 3 in 1 oil for almost 48 hours, they were very wet with oil when I first assembled the motor. All I can think of is the new Audio Silente sintered bronze bushing on top was still thirsty and with the heating and cooling cycles the top bushing pulled the oil from the top felts. The bottom felts where wet as one would expect.


Thank you, That makes sense. I left them as is.
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Did you happen to polish the shaft? The motor should not be hotter with the new coils unless Mr. Audio Silente did something wrong when he wound them. Only other possibilities here is that your alignment isn't perfect/your rotor is unbalanced or your oil is too heavy and is bogging down the motor causing excessive heat. I have another thread going with motor rebuilds I've done. I've done two rebuilds (working on the third today) and gotten ~1750rpm on both. Take a look at my power consumption numbers and compare to yours. Should be under 10 watts or around 11 with the table reassembled.
 
Simone told me there are hot motors and there are cool motors, hot motors run about 60 C, close to what mine is running. I used 3 in 1 motor oil (SAE 20) as many others have used. 1740 RPM indicates very good alignment. Yes I polished the shafts, before first and before second rebuild. I don't have a watt meter as yet and my amp meter won't read that low. Maybe tonight I'll pull the black wire from the terminal block and put my Fluke DMM in line to read amp draw and calc watts. Right now I am running 1742 RPM holding low 130's F for temps. I just was surprised my top felts were almost dry, that new bearing was thirsty. Simone confirmed my Ohm reading for the new coils. I'll check out your threads, Thank you.
 
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