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Vinyl Asylum Welcome Licorice Pizza (LP) lovers! Setup guides and Vinyl FAQ. |
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Vinyl Asylum Welcome Licorice Pizza (LP) lovers! Setup guides and Vinyl FAQ. |
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In Reply to: STILL not there. posted by ddarch on September 10, 2006 at 17:19:13:
Hi Dave,More stuff to try...
When reinstalling the motor pulley, tighten the black screw first, then the nickel (shiny) one.
If all else fails, a thicker oil (more viscous) will cause more drag on the bearing shaft and slow things down. I suggest Mobil 1 synthetic - don't overthink the oil thing. Try a 20W or 30W oil if all else fails - it will slow the platter somewhat.
(I have the opposite problem and I use Mobil 0W-15 in my main bearing)
That said, you are NOT going to do anything to the motor wiring or circuitry that will cure this issue. A bit o' theory might explain why not...
Thorens motors are designed to run on 50Hz or 60Hz (by flipping the pulley) and to work with 3 different voltage ranges (by commutator selection). There is no external capacitor, resistor, etc. that affects motor speed. It is what it is as wound by the factory.
Next, by changing from the 100-120 to 125-150 range on the commutator, what you are doing is lowering the torque the motor puts out, not the revs per minute. The revs are controlled by the AC mains frequency.
Speed is fine tuned by the eddy current brake acting on the stepped pulley. It acts as a drag to slow the motor enough to hit the exact speed. Moving the magnet closer to the pulley (actually the small movable plate underneath the pulley), increases the braking effect.
With the above in mind, if you've switched the commutator to the 125-150 range AND moved the crescent moon magnet very close to the stepped pulley the unit "should" be running so slow you can't get it anywhere near 33.333. Oops.
What else could be wrong?
One answer is - are you aligning the magnet when you adjust it so the spacing is uniform between the curve of the magnet and the curve of the pulley? A uniform distance across the curved face of the magnet allows max braking. If the magnet is skewed (one end of the crescent is significantly closer than the other) you won't be getting the optimum braking force.
Now for some weird stuff...
It could be that your house AC is running faster than 60Hz (don't laugh, your local utility can vary the mains frequency within certain tolerances so long as the average freq every 24 hours = 60Hz. Otherwise all the electric clocks would run fast or slow).
AC voltage variation will also cause speed variation by varying the torque the motor puts out - then it runs faster or slower but only due to the interaction with the eddy brake, not because the motor spins faster. Again, the motor revs are set by the AC frequency, not the voltage.
At my place, the voltage and frequency are both lower during peak usage periods (business daytime), and much higher at night. I usually have to slow the TT down once or twice between 7PM and midnight. If your utility provider is playing catch-up at night and that's when you're trying to figure this out, you will always run faster than average. Try on a weekday afternoon sometime to see the difference.
I'm not suggesting this is your problem but you should be aware of the situation so you're not freaked out by the TT running faster or slower over a 5 hour period.
Back to your situation -
It sounds like the winding of your motor is such that it runs faster than the pulley(s) ratios and eddy brake can compensate for. In other words your motor may be at the high end of the acceptable speed range just as mine is at the low end.
So...adjust that magnet close to the pulley. Align it properly. Set the commutator at 125-150, and put some 30W Mobil 1 in the main bearing.
If that doesn't slow it down enough you'll need a mains AC frequency regenerator to drop the line freq down a few Hz. Or you could have the motor pulley machined a bit smaller (but be very careful).
Lowering the line voltage won't help - that's what the commutator adjustment does (effectively).
Sorry this was so wordy but the more you know the better chance you have of making this work.
Good luck,
Pete
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Follow Ups
- Other possibilities (longish)... - Pete Fowler 20:27:36 09/10/06 (0)
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