Thorens mk 166 motor housing shorted

[batkovan]

Greetings, a newcommer here.

I have undertaken the 'motor ticking' repair caused by worn bearings - drilled the spacers out, opened the motor and placed a washer(will post pictures in the futture when everything with the TT is sorted out). Closed the motor, soldered the wires and then plugged and switched on the turntable. The motor was runing so smooth and silent that I wanted to hold it in my hand and see if I could feel any vibrations but before that I cheked with a lamp tool for voltage leakege or any shorted metal parts. And as it is sometimes at the end comes a bad surprise - the motor housing was shorted showing full voltage(thank god i did not touch it) and logically the plynth and so on every metal part in the chain that comes in contact with the motor.

I think I pulled off the mechanical part quite ok but face now electrical problem and i'm confused how can the motor run so nice and in the same time every metal part be shorted..

The windings were encapsulated in plastic so it is unprobable that they shorted. >>

I found this motor wiring diagram on the net >>

In my case it is the 220V version.
Here the wiring of the motor>>

Didn't have time today to find what exactly is going on, but tomorow I plan to unsolder the motor, check the resistance of the windings(I read in other post it shoul be around 4,6k).

Should the motor wires have continuity, if yes which ones?
Anything obvious or else that comes in mind that I should check?

Anyhow I will update my findings here, so this thread will be kind of logbook for me.

 

[gadget73]

Ohm check it and see what it shows to case. I would expect infinite resistance from any winding.

pretty sure all 3 wires will have connection to each other.

 

[batkovan]

Thanks guys. It was a false alarm as Tom forsaw - I thought something was wrong because my lamp tool lit up (sorry about the dark picture)

I checked up today with multimeter and the results are -
Windings - 4,5 and 4,49 kOm
Windings to housing - infinite resistance
Voltage leakage at the motor housing - 0,3V (can someone with Thorens check up this number with ungrounded turntable?)
Voltage leakage at the plynth/base 0,1V.

I asume leakages are expected, am I wrong?

Also the wiring diagram of my unit is different - probably the previous owner tweaked it to be more precise. >>

I puted the TT together and it works fine - very happy that I could pull that repair off - here a short representation >>

 

[gadget73]

I see, a non-contact voltage checker. Those work on induced voltage, so they will pick up magnetic fields created by motors or other things connected to a live wire.

A very small amount of voltage on the case is normal. Its just induced from the motor coils. Its low voltage and will be at very low current. Not enough to cause any trouble.

 

[batkovan]

I am planing to do a wooden frame and I could redo the wiring as in the manual as well.

well except the values of the resistor and the caps which I will reuse.

I'm just wondering if it is worth it. I measured today the rpm's with the rpm app(I know that it is not exact measure, but still) and it is pretty close - 33,8 rpm.

 

[batkovan]

Than it is really strange. I am almost certain those were factory solder joints, because they were so nice and clean(unlike mine now) and the motor was wired that way. In fact with this kind of arrangment of the elements on the wiring hub you can not wire the motor like in the service manual (assuming those were factory solder joints). Here on the left side the resistor and the capacitors(see the clean and nice connections) - the resistor 10kOm is between the top left pin(1st) and 3rd, and the 0,15 capacitor is in series - between 3rd and 4th pin.

Either those capacitors and resistor were rearanged in the past or they were soldered wrong at the factory.

 

[batkovan]

Someone may find this usefull - i did the wooden frame and rewired the motor like in the pic above(same as in the service manual for my model TD 166 mk II) and my motor started to rotate backwards(anticlockwise). I swapped the red and blue cable of the both windings and now it spins in the right direction . The RPM app still shows 3,66 though - but it is ok. However when selecting 45 rpm the belt has hard times going up the pulley as in this thread https://audiokarma.org/forums/index.php?threads/thorens-td160-super-wont-play-45-rpm-video.887009/

my belt is genuine thorens and I cleaned it, also the pulley and the inner(black plastic?) platter with almost pure ethanol(96% alc.) but it still won't go 45 rpm. Tried to play with the azimuth spring but slightly tilted either side did not fix it. I would buy a new belt if I was sure that this is the very reason why it won't play 45rpm. The pulley somehow can't grab the drivebelt, I'm wondering if I sand with say 1000 gritt sandpaper little bit the exact intersection where the pulley should grip/bite and swap the drivebelt to 45 rpm(the half bottom side of the top plastic part of the pully) will solve this or is that a very bad idea which will ruin the pulley?

a few pictures with the new frame