Do Elac 10H, 40H and 50H turntables run fast due to pulley diameter?

[monkboughtlunch]

The Papst motors spin at the correct speed. It’s the inaccurate factory pulley with poor sizing tolerance that’s the issue.

This is probably why Elac added an adjustable strobe and tapered pulley on the 770H and 50H II.

 

[Bicyclist]

I sanded down the idler pulley with 120 grit and now app reading gives between 33.34 and 33.38. Good enough for me. The amount of material shaved off amounted to two pinches of aluminum dust. I am using the RPM Speed and Wow app. The developer is/was a member of vinylengine and there's a thread there and users believe it to be reasonably accurate. Of course it won't be as good as lab tested measurements, but for the purposes of troubleshooting and gauging if your table is near spec, it's pretty darn useful.

The idler shouldnt effect platter speed. Its diameter is non critical.

 

[monkboughtlunch]

The idler shouldnt effect platter speed. Its diameter is non critical.

Correct. The pulley will respond to sanding but not the idler.

 

[wushuliu]

The Papst motors spin at the correct speed. It’s the inaccurate factory pulley with poor sizing tolerance that’s the issue.

I think that was the case for my table . The motor seems to be just fine (incredible considering its 50yrs old). I checked every other part of the table. If shaving off such minute amount corrects the issue that does seem like the pulley was machined at the edge of tolerance. Which I guess isn't that surprising considering it was made before table design reached its peak.

 

[WaynerN]

Did you ever check the speed with your stylus dragging in the grooves. Part of the measurement process is incomplete.

 

[monkboughtlunch]

I think that was the case for my table . The motor seems to be just fine (incredible considering its 50yrs old). I checked every other part of the table. If shaving off such minute amount corrects the issue that does seem like the pulley was machined at the edge of tolerance. Which I guess isn't that surprising considering it was made before table design reached its peak.

Agree. My theory: Elac designed an oversized pulley for the non-H standard models with cheaper induction motor made by Perpetuum Ebner. Those non-H motors had oversized pulleys as the US power system in the 60s had a wide range of voltages.

Of course the superior H Papst motor is immune to the voltage fluctuations because it locks to the 60Hz mains frequency.

So the evidence suggests that Elac decided to reuse the same oversized induction motor pulley on the higher end Papst models. Maybe Elac was trying to cut costs and decided to make just one pulley that would work with both the induction and Papst motors—instead of making a dedicated pulley precision sized for the Papst.

 

[monkboughtlunch]

Interestingly, a cheap rubber o-ring from a hardware store will work as a replacement for 10 and 10H idlers. Noise floor seemed a little higher. There are different o-ring durometers one could experiment with. Durometer can impact platter speed if the idler functions as a speed reducing gear.

 

[monkboughtlunch]

Did you ever check the speed with your stylus dragging in the grooves. Part of the measurement process is incomplete.

In my experience, a 10H platter with stylus in the groove spins about 1% fast at LP speed with stock pulley and stock idler.

The pulley is press on and can easily be replaced. In theory, someone could calculate the correct pulley diameter for each step and 3D print a pulley that’s dead on accurate for a Papst motor since it locks to the mains frequency. The government is obligated to ensure the mains frequency is kept to tight tolerances, and this means your Papst motor spins at a very accurate speed.

 

[wushuliu]

Did you ever check the speed with your stylus dragging in the grooves. Part of the measurement process is incomplete.

While shaving the pulley I used a 13.8oz Music Mat, which should more than make up for any stylus drag. With the stock mat, speed goes back up only just a little to ~33.4.

Just a reminder my table is a Trio PC-350 belt/idler, not an Elac.

As for app skeptics I just came across this on audiogon:
"I think the one called RPM Speed and Wow on Android has the edge. I checked that one against my industrial strobe and it was surprisingly accurate."

 

[monkboughtlunch]

A KAB speed strobe confirms the press on pulleys Elac used for the “10H” Papst model were oversized and likely borrowed from the cheaper “10” model with budget Perpetuum Ebner shaded pole motor.

 

[cafe latte]

A KAB speed strobe confirms the press on pulleys Elac used for the “10H” Papst model were oversized and likely borrowed from the cheaper “10” model with budget Perpetuum Ebner shaded pole motor.

I am too late to this thread to stop people sanding pullies. Often the problem of old idler drives going fast even with new old stock unused idler wheels is slightly hardened idler wheel rubber. New and soft there is a degree of creep, and soft mean quiet too. Older rubber is more noisy and no creep and 1% fast is common.
What the real fix should have been was a new idler rubber ie brand new not new old stock.
Chris

 

[monkboughtlunch]

I am too late to this thread to stop people sanding pullies. Often the problem of old idler drives going fast even with new old stock unused idler wheels is slightly hardened idler wheel rubber. New and soft there is a degree of creep, and soft mean quiet too. Older rubber is more noisy and no creep and 1% fast is common.
What the real fix should have been was a new idler rubber ie brand new not new old stock.
Chris

I agree in theory, but one can install a brand new 10h idler ring from the guy in Hong Kong on eBay and there is no appreciable difference in speed vs the original idler. I think at least for the 10H that Elac had some sloppy pulley tolerances. It must have been an issue back in the day when the idler wheels were still new because Elac introduced a strobe and tapered pulley allowing fine tuning adjustment on the 770H and 50H II.

 

[cafe latte]

I agree in theory, but one can install a brand new 10h idler ring from the guy in Hong Kong on eBay and there is no appreciable difference in speed vs the original idler. I think at least for the 10H that Elac had some sloppy pulley tolerances. It must have been an issue back in the day when the idler wheels were still new because Elac introduced a strobe and tapered pulley allowing fine tuning adjustment on the 770H and 50H II.

Or he is using a different rubber..
Chris

 

[td126mk2]

From the german service manual:


This means to check the height of the idler wheel (outer rubber-ring of the wheel) and the health of the (rubber) wheel itself. It must be soft and clean.
If everything is ok, it shoult not run slower/faster than 0,5%

10 and 10H idler wheel mechanic ist the same


So, maybe your 10H is running correct and you measured 1% , but it is only 0,5% ??

 

[cafe latte]

From the german service manual:View attachment 1752092


This means to check the height of the idler wheel (outer rubber-ring of the wheel) and the health of the (rubber) wheel itself. It must be soft and clean.
If everything is ok, it shoult not run slower/faster than 0,5%

10 and 10H idler wheel mechanic ist the same


So, maybe your 10H is running correct and you measured 1% , but it is only 0,5% ??

Soft rubber makes quite a difference, if wheels are made of slightly harder rubber the turntable will run fast. You dont want slow as that is more audible so slightly fast is better, but I really would be looking at the idler wheel first.

 

[illinoisteve]

My 50H runs a bit fast, according to a 33 rpm strobe disc running without any needle contact. The strobe marks s-l-o-w-l-y shuffle around instead of standing still. I can't hear any difference in the sound when I play LPs. It's my impression that I would have to have a 50H II in order to have speed adjustment, not that their might be a hack of some kind. I WOULD NOT sand down the motor pulley, since I may be using the 50H as my main TT for playing 78s later, and, if the pulley is more accurate at that speed, I don't want to screw that up. Right now my 50H is waiting for refurbishing while I've gone back to using my Dual 1229 in my system for a while. I love 'em both.

 

[cafe latte]

My 50H runs a bit fast, according to a 33 rpm strobe disc running without any needle contact. The strobe marks s-l-o-w-l-y shuffle around instead of standing still. I can't hear any difference in the sound when I play LPs. It's my impression that I would have to have a 50H II in order to have speed adjustment, not that their might be a hack of some kind. I WOULD NOT sand down the motor pulley, since I may be using the 50H as my main TT for playing 78s later, and, if the pulley is more accurate at that speed, I don't want to screw that up. Right now my 50H is waiting for refurbishing while I've gone back to using my Dual 1225 in my system for a while. I love 'em both.

Yes people are too quick to jump in and start advising irreversible mods. Going fast is really likely hard rubber, when you sand a pulley It Won't be round anymore and when you replace the idler it will be slow and impossible to fix.
Chris

 

[Radiosky]

My 40H is perfectly accurate.

Can you share what your pulley measurements were? Assuming any were made