Thorens TD-160 Motor Windings Question

[ficklecycler]

Hi there,

I just got a TD-160 with a motor that won't turn when powered on. I'm running through some diagnostics to try and determine what the problem is before I plunk down the money for a new (old) motor.

Can someone please tell me what the resistance value of the motor windings should read if they are good? Am I correct in my understanding that they should read a high resistance value but still have continuity? If this checks out, what should the next most suspicious component be? The power cord and switch are all totally functional.

Many thanks!

 

[Kico]

This may help...

From my notes during the upgrade of my TD-160, the motor windings measured resistance at 4630K ohms. If I'm wrong on this, I'm sure another member will chime in.

 

[marcmorin]

This may help...

From my notes during the upgrade of my TD-160, the motor windings measured resistance at 4630K ohms. If I'm wrong on this, I'm sure another member will chime in.

you might drop the "K" from that, or change it to 4.6K.

 

[ficklecycler]

This may help...

From my notes during the upgrade of my TD-160, the motor windings measured resistance at 4630K ohms. If I'm wrong on this, I'm sure another member will chime in.

Thanks, seems like the motor is still good! I'm measuring 4.55k on one and 4.6k on the next. So does the answer come down to one of the two little caps?

 

[marcmorin]

Thanks, seems like the motor is still good! I'm measuring 4.55k on one and 4.6k on the next. So does the answer come down to one of the two little caps?

possible, also remember that the PM pole piece must have 3 areas of magnetism. I've had PM motors go bad both ways, bad coils, and bad rotors.

 

[ficklecycler]

possible, also remember that the PM pole piece must have 3 areas of magnetism. I've had PM motors go bad both ways, bad coils, and bad rotors.

Wow, had no idea that was possible. Thanks for the lead.

 

[muovimies]

I'd say it's most probable the phase shift capacitor has gone bad - I don't recall the value of the top of my head but it's all in the service manual. It's what provides the 90 degree phase shift between the motor coils.

 

[ficklecycler]

So just to do a little update, it WAS the phase capacitor that was bad. I put everything back together and fired it up. Running nice and steady. I am a little concerned that the motor seems to be introducing vibrations into the plinth. I know that's why the suspension is there, but how much vibration is normal? You can't hear it with your ear next to it, but you can feel it in your fingertips when you touch the deck.

Next up on the list, replacing the bad RCA plug, then cleaning it, then setting up the arm, and so on and so on.

 

[bob06]

As far as the vibration goes check the pulley shaft and see if it is bent. Those motors are known for having bent shafts.

 

[muovimies]

What was the value of the cap you replaced it with? AFAIK Thorens used two values, maybe they were 0.15µF & 0.33µF but I might recall wrong. But the actual optimal value will somewhat depend on the motor. In an optimal situation both coils would get exact same voltage and the phase shift would be exactly 90 degrees - with a simple cap that's rarely the case. Any deviation from that optimal situation will result in more vibration. I actually tried 3 or 4 different values for my motor and checked the vibration patterns and settled on the best compromise. Don't recall what I ended up with.

If you detach the belt and rest the stylus on the still platter with the motor running, absolutely no vibration should be heard as hum. The same with the belt on (but of course you can't try it this way), if you can hear rumble with a TD-160 something is wrong or at least less than optimal. I don't have mine setup atm so I can't try how much the motor actually vibrates, but combined with the lack of a proper powersupply for getting the voltages just so, it is a weak part of the design IMO.

 

[gadget73]

Wear in the motor thrust bearing will also tend to produce vibrations. Usually you'll hear it in the form of "knocking". There are a couple of fixes but they're all basically the same. Essentially something is fastened onto the bottom of the motor to provide a new thrust bearing in place of the old one. I think its VinylNirvana that sells it, but its basically a plastic sleeve with a threaded hole in it. A ball bearing, spring, and set screw go into it. The bearing sits against the motor shaft as the thrust bearing, the spring provides preload, and the screw holds it all together.


Wear in the thrust surface under the spindle bearing might also introduce some vibrations. Pull the inner platter out of the well and have a look in there to see if there is a dimple.

Higher frequency vibrations could be that the phase isn't quite perfect. Someone was selling a service where they profile your motor and install the optimal cap value to provide the precise phase offset that your motor needs to run it's smoothest. I think they used either a microphone or an accelerometer attached to the motor and they tweak the cap value to get vibrations to a minimum.