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Old 30th March 2008, 08:45 PM   #1
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Default Thorens TD-125

I've been trying to repair this turntable.

I've replaced a 2N2218 transistor which was bad. Also replace the ).1 Mf capacitor from the wein bridge to the phase shifter.

I don't have an oscilloscope, only a VOM meter. I measured 3.2 vAC between the Wein Bridge oscillator and ground; and 4 Vac between the phase shifter output and Ground. But, the motor does not turn.

What could be the problem? Could the motor be the problem?


Ken
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Old 30th March 2008, 09:04 PM   #2
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Can you measure some voltage across the motor poles? I looked at the schematic but must admit not to understand how it works so bear with me if this questions seems stupid.

/Hugo
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Old 30th March 2008, 11:48 PM   #3
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OK. More mystery.

I was able to adjust both voltages (stage 1 and 2) to 5 Volts on the 33 RPM position.

But after I connected the motor, the motor still does not turn. And now, the voltage on stage 1 is around 3 volts, and on stage 2 is zero.
Disconnected the motor, voltages still measure the same.

What could be the problem?

Maybe the motor is shot?

To answer Netlist questions, now the voltage from "red" to ground is 3 vAC; and from "Blu" to ground is zero.

Ken
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Old 31st March 2008, 09:41 AM   #4
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2N2218................................is it a MKII???

If it is then you don't need an oscilloscope.

I went through the entire board on a MKII last month. It had to have been the motor. Nothing else was left. I even replaced the 709 opamps.

The 2N2218s and 2N2904 would get very hot and the motor would slow down and stop.

The motor never even got warm.

There are two windings in the motor. Evidently even the slightest short causes the circuitry to overheat. Mark
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