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Thorens TD-124 running too slow with Audiosilente idler wheel (but runs fine with original idler)

GordonW

GordonW

Speakerfixer
Subscriber
This is a puzzler.

I have a TD-124 here for cleanup and some parts updates (motor springs, plinth, arm change, etc).

One of the things to be installed, was a new idler wheel. This is one of those, with the machined aluminum hub, and a fat o-ring as the friction surface.

I got everything installed- and when I started it up, it couldn't be brought up to speed. The speed adjustment seemed to do virtually nothing- or, at least, it didn't get even close to the correct speed (way too slow).

As it had been working- I tried changing the belt- no difference.

I then took off the new idler wheel, and put the original back on- voila, CORRECT SPEED.

The owner just sent me ANOTHER idler wheel- an Audiosilente, which apparently is very highly regarded. Put it on- SAME PROBLEM- way too slow. And again- putting the original idler wheel back on, restored speed to its normal adjustment range.

Anyone seen this before? The only thing I can obviously see, is that the new idler wheels seem to be ever so slightly larger in outer diameter than the original (I mean, by a few millimeters), and the friction surface is round (o-ring outer surface) on the replacement idler wheels (as opposed to a flat surface on the original wheel).

I made sure the idler wheels are all installed in the correct orientation (the extended part of the bearing hub facing down). Just like the original was installed.

I'm thinking, that since the original idler wheel works fine- there's fundamentally nothing wrong with the turntable...

Any ideas?

Regards,
Gordon.
 
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You may have oil on it. Give the o ring a good clean.
If it's on of the new ground wheels do not remove the O ring.
Also make sure the inner rim of the platter is clean and free of oil
 
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Hello. Is a new idler rubber softer than original? If it is the contact area of the pulley and idler is to big and in practice makes the diameter of the pulley smaller than it really is. Round cross section works against you also. The plater runs slower. Robert.
 
robnec said:
Hello. Is a new idler rubber softer than original? If it is the contact area of the pulley and idler is to big and in practice makes the diameter of the pulley smaller than it really is. Round cross section works against you also. The plater runs slower. Robert.
Click to expand...
Yep a softer (quieter) can also mean slower. Selecting the correct rubber for an idler tyre is not simple many are too soft.
Chris
 
Audiosilente does a great job providing parts for these tables. Is there a noticeable change in wow & flutter with it? If so it may be oily as suggested earlier. Have you reached out to Audiosilente? Might be worth asking.
 
Check the bearing in the new idler wheel. When you install it, does it spin freely by hand with the table in the OFF position, or does it feel like it's binding? After doing some work on my TD124, my AudioSilente idler wheel wouldn't spin freely, resulting in the same slow platter speed you describe. I contacted Simone of AudioSilente and he said the inner surface of the bearing probably picked up some dirt while it was off of the table. Sure enough, I cleaned the inner surface with a Q-Tip and alcohol, re-oiled it, and it spun like a champ.
 
Just wanted to say I installed an Audiosilente idler wheel w/sintered bushing today on my mkI and the low rumble I had been experiencing almost completely disappeared. The difference in audio quality is very noticeable.
I'm very happy with this upgrade :)
 
I tried an audiosilente idler on my 135 but the original was still quieter and maintained more consistent speed better. My original idler is in exceptionally good condition; soft and no flat spots. I treat it occasionally with old school brake fluid
 
GordonW said:
This is a puzzler.

I have a TD-124 here for cleanup and some parts updates (motor springs, plinth, arm change, etc).

One of the things to be installed, was a new idler wheel. This is one of those, with the machined aluminum hub, and a fat o-ring as the friction surface.

I got everything installed- and when I started it up, it couldn't be brought up to speed. The speed adjustment seemed to do virtually nothing- or, at least, it didn't get even close to the correct speed (way too slow).

As it had been working- I tried changing the belt- no difference.

I then took off the new idler wheel, and put the original back on- voila, CORRECT SPEED.

The owner just sent me ANOTHER idler wheel- an Audiosilente, which apparently is very highly regarded. Put it on- SAME PROBLEM- way too slow. And again- putting the original idler wheel back on, restored speed to its normal adjustment range.

Anyone seen this before? The only thing I can obviously see, is that the new idler wheels seem to be ever so slightly larger in outer diameter than the original (I mean, by a few millimeters), and the friction surface is round (o-ring outer surface) on the replacement idler wheels (as opposed to a flat surface on the original wheel).

I made sure the idler wheels are all installed in the correct orientation (the extended part of the bearing hub facing down). Just like the original was installed.

I'm thinking, that since the original idler wheel works fine- there's fundamentally nothing wrong with the turntable...

Any ideas?

Regards,
Gordon.
Click to expand...
The diameter of the idler wheel does not change the gear ratio. It is an idler which only transfers motion to the platter. My suggestion is to check and see where the idler is running on the motor spindle. If it is a little hi or low it will cause this. You may need a washer to change it's position.
 
Thunderbox said:
It's idler drive no belt.
Click to expand...

The TD124 has an idler and a belt. It's a different setup than a garrard, bsr, dual, etc. The belt drives an intermediate pulley, which then drives the idler. I think they did this to reduce motor noise. The belt can wear out and shed black goo all over the pulleys, affecting speed.
 
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My 2 cents;Check that the o-ring is running concentric , clean with isopropyl alcohol and check that the stepped pulley gets proper engagement, adjust if needed.
I have the Audiosilente idler wheels in my two Thorens 124 ( Mk I & Mk II )and I have never encounter any problems whatsoever ( so far so good!)
But just don't bolt on and hope for the best, check and adjust and measure every parameter so that everything is running smoothly.
The service manual is always of great help!

124mk2_idler_adjustment400.jpg
 
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zwuttoo said:
My 2 cents;Check that the o-ring is running concentric , clean with isopropyl alcohol and check that the stepped pulley gets proper engagement, adjust if needed.
I have the Audiosilente idler wheels in my two Thorens 124 ( Mk I & Mk II )and I have never encounter any problems whatsoever ( so far so good!)
But just don't bolt on and hope for the best, check and adjust and measure every parameter so that everything is running smoothly.
The service manual is always of great help!

View attachment 3596436
Click to expand...
O ring idler wheels are not great. I have made them myself, and no O ring is the same diameter all round. They have lumps and bumps so they introduce wow and most are the wrong hardness of rubber.
I glued on oversized o rings of the correct hardness and machined the rubber which is the only way to do it, even then a bonded idler is better.
Chris
 
cafe latte said:
O ring idler wheels are not great. I have made them myself, and no O ring is the same diameter all round. They have lumps and bumps so they introduce wow and most are the wrong hardness of rubber.
I glued on oversized o rings of the correct hardness and machined the rubber which is the only way to do it, even then a bonded idler is better.
Chris
Click to expand...

O ring idler wheels are not great.
Click to expand...


I know and that's probably why no one who owns a TD124 uses them!:jump:
 
Thunderbox said:
The diameter of the idler wheel does not change the gear ratio. It is an idler which only transfers motion to the platter. My suggestion is to check and see where the idler is running on the motor spindle. If it is a little hi or low it will cause this. You may need a washer to change it's position.
Click to expand...
If there is a belt driving a smaller pulley on the idler shaft the ratio can be changed.
 
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