Thorens TD-147 Spins backwards

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jayk
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Thorens TD-147 Spins backwards

Post by jayk » 16 Jan 2020 22:42

I'm bringing a td-147 back to life but not having luck fixing this problem yet. On startup it starts spinning counter-clockwise looking down from above the table. I've replaced the startup cap (4.7uF iirc) and same thing happens. The wires from the motor seem like they may have been mucked with at some point but from what I can see in images.google it's wired the same as other tables. Black-black-blue-red.

Any ideas?

jayk
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Re: Thorens TD-147 Spins backwards

Post by jayk » 16 Jan 2020 23:33

So, in the spirit of experimentation I checked voltages across 1-3 and 2-4 on the motor while it is running backwards and found -20 and -18. I then decided to take it a step further and reversed red and blue and the two blacks and lo-and-behold it spins the correct direction. I've unplugged and turned off everything now while I consider.

Is it just coincidence that reversing the wires corrects the spin direction? Is there still an underlying problem? Maybe it was wired incorrectly by a previous "tech". Or - Maybe I installed the cap backwards? I didn't see a polarity indicator on either the replacement or original.

It starts up solidly and spins with authority so the motor seems ok.

medwaybeat
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Re: Thorens TD-147 Spins backwards

Post by medwaybeat » 17 Jan 2020 12:44

I doubt it was the way you installed the cap as most are non polarised these days.
I had the same issue with mine but it was very obvious the previous owner had had a go at rewiring it.

Pauw
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Re: Thorens TD-147 Spins backwards

Post by Pauw » 17 Jan 2020 13:50

If you "backwards wire" a four pole motor you set up a situation where the field and coil current are out of phase and thus it will spin backwards. :D

jayk
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Re: Thorens TD-147 Spins backwards

Post by jayk » 17 Jan 2020 16:18

I worry that something else is causing it to spin backwards and I "backwards wired" it to spin forwards again. As far as I can tell from service manual it used to be wired correctly.

Also worth noting that I am using a power supply from e-bay because it was sold without the original power supply.

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