Thorens TD 104 no motor power :(

[Terracide]

I own a TD 104 that stopped working. I pulled it apart to see if i could detect anything. When i use a multimeter i detect no power on the motor it self when it's turned on. The lights on the speed selector still work. I used another power adapter to be sure (even when i measured it) and still same. The 104 is pure manual so there is not switch that can turnoff the motor.

I used a service manual: http://www.kevinchant.com/uploads/7/1/0/8/7108231/thorens_td104_105_service.pdf But i do not have much experience in this. I tried to measure the points that are known as testpoints, they all have voltage but they are all a bit lower as suggested. I measured the C112 capacitor that is the 25v, and that one still holds 24.7 so that one is probably ok. C113 looks a little dark on one side, i cannot measure it when it's soldered in but can C113 be my problem? I have a testtool that can measure capacitors but then i need to solder it out.

When i look at he diagram the T109 and T110 (part of the motorboard) should deliver 18V but they have 14.5 and 13.5V (with no load). So my guess (and i am a noob) it looks like the board has bad capacitors on the power circuit that deliver voltages too low....?

Anyone with more technical skills have any suggestions?

 

[BinaryMike]

I would first disconnect the motor's power input wires and apply 2~3VDC from a power supply or maybe just a 1.5V battery, to make sure it's not shorted and capable of normal operation.

 

[elnaldo]

In the service manual you have a detailed explanation of the motor drive circuit, and the speed selector circuit.

It says " The DC Motor is fed from Z 102-1 trough T104". I'd start checking voltages at T104, Base, Collector and emitter.

There is a Logic IC involved in the speed selection too, and the stop function, I think you should check voltages at that IC, check if the HI and LOW voltages explained in the service manual match your circuit.

Of course, check if the motor is OK.

You need to check at Zener diode D106, 10Volt across it, and check test point "C" for 10 Volts. And Zener D107 (test point "D"), for 4.7V DC.

T109 and 110 don't deliver 18V, they close the 18V circuit to ground, through the LEDs, to light the speed selected. If the LED light, T109 and 110 are working. (18V come from the PS, go to the LEDs, then to the transistors, when transistors are conducting, the circuit is closed to ground through R158)