Ar Tt Wobble

[rl1856]

Hello,

I have both an ES-1 and XA. Platters on both exhibit some wobble during rotation.

I have checked the motor shaft, pulley, bearing shaft and inner platters on both TT. No issues. The motor shafts do not have any horizontal movement, the pulleys are level and do not oscillate in any way. The bearings are clean and the inner platters spin true. Spinning just the inner platters only, there is no wobble that I can detect, either spinning freely or when driven by the pulley.

Inverting the outer platters, so that I see the path of the belts shows no deviation in the belt path.

When I put the outer platters on correctly (or even switch them between TT), I can see a perceptible rotation wobble. There are times the movement is audible such as when a a single note is sustained.

Anyone else notice this with their AR tt ?

Is the cure to have the out platters balanced at a machine shop ?

Thanks,

Ross

[pivot]

Does the platter itself wobble because it is out of round or does it cause the suspension to oscillate due to imbalance?

I have had my platter rebalanced and match marked by George Merrill decades ago. Even before that however I do not recall a wobble, either visual or audible.

What are you using for plattermats? Is it possble the mats are out of balance or not flat? With mats off do you see the wobble?

Have you tried adjusting the suspension springs?

[Conrad Hoffman]

Remember that machining errors (and there will always be errors) get magnified at the outer edge of the platter. It may be possible to find the low spot and apply a piece of thin tape to the inner platter so the outer runs true. I'd probably build up three places for proper kinematic support and no rocking. I don't believe one could hear this, as the error is usually way less than record warp, and at a 1.8 second interval. That said, the AR tables I've seen all run dead true.

[Alec124c41]

Are you seeing the edge of the platter move in and out, or up and down?
Or are you seeing the tone-arm move sideways?

Cheers,
Alec

[rl1856]

First thing I did was to check that all was level....wall shelf, top plate and platter are all level.

The platter moves up and down, like a slight flutter. I have observed this when looking at the platter only, without mat.

The platter does not move side to side, only up and down. I have not observed any deflection of the suspension.

With a flat record, the movement is enough to cause the tonearm to move up and down slightly.

It occurred to me that the problem could be on the inner surface of the outer platter, where it makes contact with the inner platter.

Suggestion to use tape to address the low spot is intriguing but first I have to identify the low point....

Thanks !

Ross

[pivot]

Are you sure the outer platter and subplatter are going together right?

Top seam between inner and outer platter should be snug, flush and level once they are joined.

I would make sure the mating surface between platters was clean and free of anything that could interfer. Don't be afraid to do a little light polishing.

[rl1856]

Inner/outer platters are correctly mated. If not there would be side to side movement of the platter.

Hard to measure that both surfaces are level because the weight of my level causes the suspension to deflect.

I will examine the mating surfaces more carefully.

Thanks,

Ross