100Hz hum: Motor noise?

[discosdecorte]

Dear fellow trolls,

I've recently purchased a diamond stylus for my Hara M-180. It was an important improvement, sonically speaking, but it also helped me to reveal a 100Hz hum in my lathe. I think it may be motor noise, because I've tried to cut a silent groove without input signal, no heating wire, no computers or power supply units near... nothing. I've tried in several power sockets around my home. The 100Hz hum is there everytime. In fact, I can hear it when I put my ear near the Hara with the motor running. Here the current frequency is 50Hz, so it should be the second harmonic, as grooveguy states in this thread: https://www.lathetrolls.com/viewtopic.php?t=6122#p38541. Right?

Maybe the hum is inevitable in a so small unit, I don't know... It is not audible at all when the music starts, but I don't like it to be there. I can still hear it between tracks or at silent passages. There must be a way of isolate it from the head, to avoid the 100Hz to be recorded in the blank! Any suggestions?

Clip: https://drive.google.com/file/d/16oV9rvlZ4TYtoBxcLHnPTqDCoBh8svkn/view?usp=sharing
Freq. graph: https://drive.google.com/file/d/13oZ-WSpIfi8hQlB-UIu8Y3EDxuGfHQSD/view?usp=sharing

Best regards,
Fer

[markrob]

Hi,

Sounds more like rumble rather than AC mains motor noise (but that could be there as well). I think I can hear some low frequency stuff that sounds like once per revolution. The spectrum is pretty broad rather than sharp like a constant tone would show. I suspect that its probably close to the limit for a machine of this type. You might look for worn out rubber shock mounts and idler wheels. Otherwise, you are probably into modification to the unit to reduce it further. You don't provide a 0 db reference to determine how far down the rumble is from a standard operating level. If you have a test record with a 5cm/sec 1Khz ref tone, play that back and set to 0 db (or note the level). Then without changing any gains, playback your silent cut and measure how far below the reference level the rumble sits.

Mark

[Soulbear]

Food for Thought??
https://www.techhive.com/article/3063590/how-to-get-rid-of-hum-and-eliminate-other-noises-from-your-audio-and-video-systems.html

[juba bc]

I had noise problems in 40hz, I discovered that it was the power transformer of the circuits, I solved the problem using a switched source

[discosdecorte]

Sounds more like rumble rather than AC mains motor noise (but that could be there as well) [...] I suspect that its probably close to the limit for a machine of this type. You might look for worn out rubber shock mounts and idler wheels.

Hi Mark! Thanks for your suggestions. I think it is rumble too. And I do certainly have a dry rotten idler wheel, as you can see here: https://drive.google.com/file/d/1CjEYNpX3nk_aiitU5NJN0q8K9utPPms5/view?usp=sharing (thanks to sgreiner1011 for letting me notice about it)

I've been looking for a replacement that could fit, but I had no success. I've just started another thread looking for a replacement: https://www.lathetrolls.com/viewtopic.php?f=4&t=8782

Soulbear, juba bc, thanks so much for your suggestions, you are very kind.

Best regards,
Fer

[Soulbear]

Hi Fer, Hope this helps
A Question from another forum : -
Q “Hi. I'm working on a suitcase record player with a rubber idler wheel drive. The original wheel was as hard as a rock, so I found another wheel with good rubber on it that was (surprisingly) easily removable. I chucked the wheel on a drill and used sandpaper to bring the new wheel down to the diameter of the old wheel, removed the rubber, and glued it in place on the old wheel. As it is now, the turntable turns at a steady pace, but the speed is just a couple of RPMs too slow. I'm wondering how the "gearing" is set up on a turntable like this”
Answer :-
A “Unless it is an RCA Victor 45 player with a two-level idler wheel, the diameter of the wheel will change the speed of the turntable NOT AT ALL. !!!
The speed is determined by the ratio of the motor spindle to the turntable inside diameter. The idler has nothing to do with it.”

Fer, this is correct, the idler tyre doesn't determine the rotational speed of the turntable. It's about surface physics, friction, and slippage... not the surface diameter of the Idler Wheel. I have literally just Skimmed on a Metal Turning Lathe, a very "Similar condition to Yours" Idler wheel for one of my Three AR Sugden Lathes :-

Skimmed Idler-1.jpeg

Un-Skimmed Idler-1.jpeg

A 2” inch wheel will spin half as fast as a 1” inch wheel, if driven from the same motor shaft at a given RPM...... however it will still drive the Platter at the same RPM speed as the 1” inch Idler Wheel did.
If Skimming your own Idler is not a readily available option do not worry!!
Don’t worry too much about getting an “Exact Replacement” it might take you forever to locate one. A “Near enough” New Idler will get the job done for you, if it is a slightly smaller diameter it will rotate a few more times in a minute than the old idler. Conversely, if the new idler is of a slightly larger diameter, it will rotate a few less times in a minute. The speed transfer between Driver (The “Motor Capstan Diameter”) and the Driven (“The Platter” will remain the same, ONLY THE RPM OF THE IDLER WILL BE CHANGED
Hope this Helps Regards Soulbear

[discosdecorte]

Hi Soulbear!

Thanks for your kind response! You are being very helpful

I remember having read about the idler size question (Terry Rubber's Rollers site has a section titled "The big idler debate" about it) You are so right, I don't need an exact idler wheel (good news!) but I am not sure how much smaller diameter will work in my Hara M-180: When moving the head to start cutting, the idler wheel moves down a little in order to touch the motor tip and the inner face of the platter at the same time. But, as you surely know, this is a small unit and the distances and margins to "play with" are veeeery few.

I think I've found a idler wheel that could fit very well. I'll let you know if it works.

Thanks a lot!
Fer

[Soulbear]

Hi Fer,
I'm curious as to whether you managed to resolve this issue, did you get the Walsco 1444 and Try it?? I was looking at the Specs here :- https://www.turntableneedles.com/Record_Player_Idler_Wheel_1444
I thought there was possibly perhaps too much of a mis-match between your Spec and the the Spec listed , Height, diameters, more especially the diameter for the Spindle?? Might it be worthwhile having go at repairing the idler yourself?? In another thread about SP10 Platter Mats ( https://www.lathetrolls.com/viewtopic.php?f=1&t=8691&p=55504&hilit=sp10+mat#p55504) Suedenim mentioned this :- https://www.ebay.co.uk/str/number1gasketshop/Turntable-Mats/_i.html?_storecat=33339673011
I just saw a YT video where a Guy got a result DIY presumably using a thicker Neoprene Mat from the same supplier :- https://www.youtube.com/watch?v=F0sgOosqf84
Thought it might be worth looking into??
Regards Soulbear

[discosdecorte]

Hi Soulbear!

Hi Fer,
I'm curious as to whether you managed to resolve this issue, did you get the Walsco 1444 and Try it?? I was looking at the Specs here :- https://www.turntableneedles.com/Record_Player_Idler_Wheel_1444
I thought there was possibly perhaps too much of a mis-match between your Spec and the the Spec listed

Yeah, I have finally ordered a Walsco 1436 idler wheel, still on its way from Russia! Specs: https://www.turntableneedles.com/Record_Player_Idler_Wheel_1436

I just saw a YT video where a Guy got a result DIY presumably using a thicker Neoprene Mat from the same supplier :- https://www.youtube.com/watch?v=F0sgOosqf84
Thought it might be worth looking into?

Very cool! Thanks, you are very kind!

Best regards,
Fer

[discosdecorte]

Hi,

Sounds more like rumble rather than AC mains motor noise...

I've tried sitting my small lathe over two layers of bubblewrap I have at home and It helped a lot with the rumble. So I am thinking about using some absorbent stuff under my lathe. What do you think? Any recommendations?

Best regards,
Fer

[discosdecorte]

Hi,

Sounds more like rumble rather than AC mains motor noise...

I've tried sitting my small lathe over two layers of bubblewrap I have at home and It helped a lot with the rumble. So I am thinking about using some absorbent stuff under my lathe. What do you think? Any recommendations?

Best regards,
Fer

Solved thanks to this: https://www.hudsonhifi.com/products/75-platinum-silicone-hemisphere-bumper-non-skid-isolation-feet-with-adhesive-20-duro-16-pack
Awesome results

Best regards,
Fer

[EposLab]

I wait my M180 to arrive! I am really curious about this mini cutting machine and looking forward in using it!

[EposLab]

Yeah, I have finally ordered a Walsco 1436 idler wheel, still on its way from Russia! Specs: https://www.turntableneedles.com/Record_Player_Idler_Wheel_1436

Well today my M180 arrived!
Its a lovely little machine but the idler wheel is not that good.
Is this 1436 wheel a direct replacement or does it change the speed?

[discosdecorte]

Yeah, I have finally ordered a Walsco 1436 idler wheel, still on its way from Russia! Specs: https://www.turntableneedles.com/Record_Player_Idler_Wheel_1436

Well today my M180 arrived!
Its a lovely little machine but the idler wheel is not that good.
Is this 1436 wheel a direct replacement or does it change the speed?

Sadly, the 1436 idler wheel doesn't fit and I haven't found any valid replacement yet!

Good luck!
Fer

[EposLab]

Oops, thats not good
Any idea of where to make a custom wheel?

[Soulbear]

Hi There

Sadly, the 1436 idler wheel doesn't fit and I haven't found any valid replacement yet!

Oops, thats not good
Any idea of where to make a custom wheel?

Stateside Trolls are lucky to be able to use the services of this gentleman :-
http://www.terrysrubberrollers.com/ However!!! His site message is that due to the Covid19 Pandemic he is not taking any orders right now. However, all is not lost

https://www.youtube.com/watch?v=UE_lePo_ZQk



Take a quick look on YT using "Idler Wheel Repairs" as the search term!! There are many Videos covering all manner of Idler Wheels, Many on Tape Recorders, and others on a variety of Turntables. Lots of Various solutions, some very simple, some a little more complex, many demonstate Great Results.
I hope this helps
Best Regards Soulbear

[discosdecorte]

Hi EposLab!

Have you checked out these links?

https://www.lathetrolls.com/viewtopic.php?f=1&t=8691&p=55504&hilit=sp10+mat#p55504) Suedenim mentioned this :- https://www.ebay.co.uk/str/number1gasketshop/Turntable-Mats/_i.html?_storecat=33339673011
I just saw a YT video where a Guy got a result DIY presumably using a thicker Neoprene Mat from the same supplier :- https://www.youtube.com/watch?v=F0sgOosqf84

Best regards,
Fer

[EposLab]

Well i was curious if the idler wheel was totally dry, so trimmed the dry & uneven top layer and found that inside seems to be in very good condition as a rubber. Living in a 50hz region lowers the speed and now is just above 33rpm! I am planning to send it to Jesus @agnewanalog for a very precise trim of the idler wheel so it will run at 33rpm. Once this is done he will make an additional custom cupstan for running at 45rpm!
I know this will take sometime cause Jesus is busy with moving but i really look forward as i fell in love with this small lathe!!

IMG_20201101_142115.jpg

[markrob]

Hi,

If its really an idler wheel, the diameter will not affect speed. Aren't these meant to run on 50 hz as they were sold in Japan?

Mark

[Soulbear]

Well i was curious if the idler wheel was totally dry, so trimmed the dry & uneven top layer and found that inside seems to be in very good condition as a rubber. Living in a 50hz region lowers the speed and now is just above 33rpm! I am planning to send it to Jesus @agnewanalog for a very precise trim of the idler wheel so it will run at 33rpm. Once this is done he will make an additional custom cupstan for running at 45rpm!

Hi,

If its really an idler wheel, the diameter will not affect speed. Aren't these meant to run on 50 hz as they were sold in Japan?

Mark

Exactly as Mark says

if it is a slightly smaller diameter it will rotate a few more times in a minute than the old idler. Conversely, if the new idler is of a slightly larger diameter, it will rotate a few less times in a minute. The speed transfer between Driver (The “Motor Capstan Diameter”) and the Driven (“The Platter” will remain the same, ONLY THE RPM OF THE IDLER WILL BE CHANGED

"The diameter of the idler wheel will have absolutely no effect on the final drive speed. The only way to change the final drive speed (short of changing the motor speed) is to change the diameter of the driving member (Motor Pulley, or in this case, the Motor Capstan) or the Driven Member ( The Platter Diameter itself)"

If the Speed is Slightly "Off" it could be any number of the other things mentioned in the earlier posts ^^^^^^^^^^^^
Caused in all probability by few thousandths of an inch/mm undersize of the Motor Drive Capstan (Being all it needs to cause this) would be my Best Guess, and a pretty easy fix if you entrust it to Jesus @agnewanalog. Totally professional and thorough, I cannot recommend his work enough
Hope this helps Best Regards Soulbear