Wobble on platter (Technics 1200)
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asdf

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There is a VERY slight wobble on a Technics 1200 turntable that I purchased (cheaply). I found a mark on the platter that leads me to believe that something may have been dropped onto it. The wobble is barely perceptible (but it's there).

I cannot see or feel any movement on the spindle. I have checked the screws that hold the spindle in place and all seem to be tight. My only guess is that the spindle may have been damaged. I planned on replacing the spindle (a new one is only $30, and it appears to be an easy job). Anyway, I thought I'd get some opinions before doing this.

If no skipping is taking place, is this worth replacing?

Thank you.

--asdf
 
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asdf

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Well, I just spoke with KAB about this issue. They are very nice and very helpful, by the way. It sounds like it is very unlikely that it is a spindle problem. Instead, it's probably one of four different problems:
  • My imagination (there's a pattern on the side of the platter that can create an optical illusion);
  • The platter is not sitting properly because I (and the previous owner) did not seat it carefully enough;
  • There are dents in the platter hole (don't remember the technical term); regardless, these can be fixed without much expense;
  • The platter itself could be warped (obviously the worst scenario).

I don't have the turntable with me, so I can't confirm the problem. I'm hoping it's just my imagination, though.

--asdf
 
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Lazarus Short

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If you hold a piece of soft chalk close, then closer, then closer, then closer to the platter as it spins, you can find the high spot if there is one, or maybe find that it is, indeed, an illusion. On the other hand, your 1200 may have the same problem mine had, and it is common to direct-drive turntables: cogging. As the whole thing turns, one part of the motor swings past the coil [or pole], and gets a boost. Before it reaches the next coil [or pole] it slows down. So, you see, it is always speeding up and slowing down - cogging. I have been told that only Hitachi Uni-Torque motors are immune to this, but then you have to settle for Hitachi. My 1200 got so bad I had to sell it for peanuts.


Worry not! There are gobs of good tables out there!

Laz
 
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Quote:

Originally Posted by asdf /img/forum/go_quote.gif
There is a VERY slight wobble on a Technics 1200 turntable


There is often a bit more play in a direct drive platter if you rock it than a belt drive as the spindle is part of the motor so the tolerances are never going to be as tight as on a belt drive. This is just part of the design and shouldn't be a cause for concern unless what you are describing is that the platter has become warped somehow and rises and falls as it spins, which would indicate more serious issues.
 
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I wouldn't worry about it, if it plays okay.
 
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Well, I haven't played it, yet. My new cartridge hasn't arrived, but I'm hoping it's waiting for me at home. I don't want to let the previous owners' cartridge get anywhere near one of my albums (even though it sounded fine on his system).

I'll have to try the chalk trick. I spent 15 minutes studying it (after reseating it), and I can't decide whether or not the wobble is actually there. That's probably an indication that it won't affect the sound. We shall see.

--asdf
 
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Quote:

Originally Posted by Lazarus Short /img/forum/go_quote.gif
If you hold a piece of soft chalk close, then closer, then closer, then closer to the platter as it spins, you can find the high spot if there is one, or maybe find that it is, indeed, an illusion. On the other hand, your 1200 may have the same problem mine had, and it is common to direct-drive turntables: cogging. As the whole thing turns, one part of the motor swings past the coil [or pole], and gets a boost. Before it reaches the next coil [or pole] it slows down. So, you see, it is always speeding up and slowing down - cogging. I have been told that only Hitachi Uni-Torque motors are immune to this, but then you have to settle for Hitachi. My 1200 got so bad I had to sell it for peanuts.


Worry not! There are gobs of good tables out there!

Laz



Cogging is theoretically an issue with all electric motors and since all the turntables I know of use them, no drive system can totally escape the problem. A turntable can be no better than its motor regardless how well the rest of it is made. Since the platters and motors on direct drive tables are essentially one, cogging should be a bit more of an issue but this is more theory than real listening experience. If an audible cogging symptom is experienced on a Technics or an other high quality turntable, I would blame a faulty motor instead of the drive system.
 
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Quote:

Originally Posted by ssportclay /img/forum/go_quote.gif
Cogging is theoretically an issue with all electric motors and since all the turntables I know of use them, no drive system can totally escape the problem. A turntable can be no better than its motor regardless how well the rest of it is made. Since the platters and motors on direct drive tables are essentially one, cogging should be a bit more of an issue but this is more theory than real listening experience. If an audible cogging symptom is experienced on a Technics or an other high quality turntable, I would blame a faulty motor instead of the drive system.


If this were the case, would replacing the spindle assembly fix the problem?
 
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Quote:

Originally Posted by asdf /img/forum/go_quote.gif
If this were the case, would replacing the spindle assembly fix the problem?


no.

if you ave audible cogging you will know INSTANTLY. it is a VIOLENT speed instability.

the technics uses a DC motor, which does not eliminate cogging, but certainly limits it compared to an AC one.

if the dot for the speed ring kind of fades in and out at a fixed pace i would nto wory too much. see if you can get the +3 or -3 dots to be still. the center "dent" bypasses the slider, and does not always EXACTLY meet 33.333RPM. it could be 33.34.
 
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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
no.
if the dot for the speed ring kind of fades in and out at a fixed pace i would nto wory too much. see if you can get the +3 or -3 dots to be still. the center "dent" bypasses the slider, and does not always EXACTLY meet 33.333RPM. it could be 33.34.



The dot for the speed ring does fade in and out (but it's barely perceptible). Are the +3 and -3 dots the ones immediately above and below the main dot? Does it matter if they are closer to +4 -4 dots?
 
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Quote:

Originally Posted by ssportclay /img/forum/go_quote.gif
Cogging is theoretically an issue with all electric motors and since all the turntables I know of use them, no drive system can totally escape the problem. A turntable can be no better than its motor regardless how well the rest of it is made. Since the platters and motors on direct drive tables are essentially one, cogging should be a bit more of an issue but this is more theory than real listening experience. If an audible cogging symptom is experienced on a Technics or an other high quality turntable, I would blame a faulty motor instead of the drive system.


Good information!

Years ago, I was shown at an audio shop two turntables: a TOTL direct-drive [don't remember brand] and one of those quirky British Connoisseur belt-drives with clock motor. The power switch included a little rubber foot which literally kick-started the platter when you yanked the lever. If you did not give the lever a good yank, the thing just would not start. Oh, please
! Both tables had the same phono cartridge, and fed the same amp and speakers. Both played the same LP. The Connoisseur won out, and the salesperson explained that it had to do with the belt-drive being a non-cogging drive system. I don't know if he was correct or if it was snake oil.

Laz
 
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Quote:

Originally Posted by asdf /img/forum/go_quote.gif
The dot for the speed ring does fade in and out (but it's barely perceptible). Are the +3 and -3 dots the ones immediately above and below the main dot? Does it matter if they are closer to +4 -4 dots?


by+4/-4 do you mean on the slider? if so thats totally OK. the numbers on the slider are just there for reference, the dots on the rim represent the actual speeds.
Quote:

Originally Posted by Lazarus Short /img/forum/go_quote.gif
The Connoisseur won out, and the salesperson explained that it had to do with the belt-drive being a non-cogging drive system. I don't know if he was correct or if it was snake oil.


the cogging effect of the motor has little to do with belt or direct drive but how the motor is built. belt drives are more tolerant of a jerky motor than a direct drive (which are completely intolerant) but FAR from immune from the ill effects. Teres audio has a good paper on why even a belt drive works better with a motor that cogs less.

the direct drive camp argues that the "short term" speed instability shown in the ittsy bitsy cogging is offset by the superior speed control compared to the belt drives when playing long notes and loud passages.

as an odd twist of fate and perhaps the pendulum simply swinging the other way, direct drives and idler drives are coming back into style.
 
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Quote:

Originally Posted by nikongod /img/forum/go_quote.gif
as an odd twist of fate and perhaps the pendulum simply swinging the other way, direct drives and idler drives are coming back into style.


Yes, indeed. I currently own one belt drive Dual, two direct drive Sonys, and one direct drive Denon [DP-11F, bought yesterday]. I was quite the belt advocate for years after my SL-1200 debacle. I can't see the need for idlers, however.

Laz
 
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Quote:

Originally Posted by Lazarus Short /img/forum/go_quote.gif
Yes, indeed. I currently own one belt drive Dual, two direct drive Sonys, and one direct drive Denon [DP-11F, bought yesterday]. I was quite the belt advocate for years after my SL-1200 debacle. I can't see the need for idlers, however.

Laz



Some of the idler people claim that they provide detail and dynamic slam beyond the capability of any belt drive turntable.They also sometimes claim that direct drive also has this same potential but a great one was never made due to motors being imperfect.
 
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Lazarus Short

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Quote:

Originally Posted by ssportclay /img/forum/go_quote.gif
Some of the idler people claim that they provide detail and dynamic slam beyond the capability of any belt drive turntable.They also sometimes claim that direct drive also has this same potential but a great one was never made due to motors being imperfect.


Idler drives also provide squeeky noises if the platter & idler are not perfectly aligned. Given that the idler is usually mounted on a comparatively flimsy pivot, this is a very real problem. I have resorted to bending parts to get things into alignment. If the table is expensive, it is not an exercise for the faint-heated.

Laz
 
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