Building a Plinth for Lenco L75

[jls001]

I wanted to share my home-made protractor - this is for making a new arm hole, and also to obtain correct overhang:

An "improved" version of the protractor. Instead of a line, there is now an arc where the tip of the stylus must rest/coincide. You no longer need to have the arm tube parallel to the pivot-spindle line. All making and usage instructions from previous post remain valid. For those interested to make your own as per your arm specifications, you can use the free vector drawing program Inkscape. In Inkscape, print the drawing to 100% scale.

Do be careful while aligning cartridge and adjusting overhang.

 

[jls001]

Ahead:
1) top layer of plinth to be changed to 10 mm thick MDF or HDF. Current top layer is 12 mm and it wrong. I end up using ad hoc fillers below the top plate and second layer to mate the top plate to the plinth. So whoever is going to build a plinth in the near future for your beloved Lenco L75, take note -- use 10 mm top layer. I went to many plywood shops but none had 10 mm thick plywood or MDF. Some shops claimed there is no 10 mm plywood or MDF. They offered 6 or 12 mm. Is it true that standard thickness is 6, 12, 18, etc mm?

2) need to decide whether to keep this plinth and complete it properly, or build something else that has caught my fancy

Some more updates:

Looked everywhere but couldn't get 10 mm plywood or MDF. I hit paydirt today. Got 10 mm plywood. Brand is MACRO. It is exactly 10 mm thick, though it is sold as 12 mm. Don't tell the Legal Metrology Dept.

I will go get it cut now.

I'm adding two 18 mm layers of plywood at the bottom to give it more mass. So this plinth build will be taken to it's logical conclusion.

 

[reubensm]

Some more updates:

Looked everywhere but couldn't get 10 mm plywood or MDF. I hit paydirt today. Got 10 mm plywood. Brand is MACRO. It is exactly 10 mm thick, though it is sold as 12 mm. Don't tell the Legal Metrology Dept.

I will go get it cut now.

I'm adding two 18 mm layers of plywood at the bottom to give it more mass. So this plinth build will be taken to it's logical conclusion.

a dumb question Joshua, can a layer of granite slab or concrete slab be used say, after layer 2 (counting from the deck, downwards), I assume the ringing effect would not come into the picture, also effective mass increases, right? Any thoughts?

 

[jls001]

It should be possible to sandwich granite layer without ill effect.

And it will certainly add to the mass as granite is denser than plywood or MDF. I have also heard of some folks filling lead shots for the added mass.

 

[sachu888]

Frank Schroeder's turntable has a sandwich Bamboo-Slate-Bamboo plinth.

Regards,
Sachin

 

[arj]

i believe , if you use granite, you must use a dampening agent (like bitumen) on it first. that cuts down heavily on the ringing.
But Slate is the Best...although no idea where you get it ..

 

[jls001]

Lots of people around the world have tried slate and they seem to universally like it. Something to do with the nature of its structural make-up. People closer home have sandstone too. I believe sandstone and slate have similar structural composition.

Update:
I tried out the 10 mm top layer last night. It is NOT a direct drop in. There are three or four screws that need to be slightly "modified" as they protrude below the pan surface and does not allow the mating of bottom of the pan to the second layer. I will take some photos and point out the offending screws. After these screws are adjusted, the top layer does sit comfortably on the plinth.

The bottom has gained two new 18 mm layers, taking the overall height of the plinth to exactly 5 and half inches. I think it makes it look much more substantial than before. I forgot to weigh it. Will do when it dismantle it for gluing.

After adjusting VTA, the TT is back in action.

 

[Rajiv]

Hi,

But Slate is the Best... although no idea where you get it ..

Billiard and Snooker table manufacturers use slate for the tables.

I asked John W. Roberts&Co.(one of the oldest Billiard table makers ) here in Madras and they said that they have Indian and Italian slate at their works,and I could have any of their left over/damaged slate .

The problem is that they have moved their works from G.P.Road in the city, to Red Hills which is a way off,and I have not found the time to make the trip to their works.

Arj, you could check out the Billiard table makers in B'lore.

Regards
Rajiv

 

[sachu888]

One of our FM told me raw Slate blocks are easily available in Kolkata @ Rs1000(approx).

Regards,
Sachin

 

[arj]

first is procuring the slate and next is getting someone to cut it to specs.
Rajiv/Sachin , thanks a lot for the pointer on slate..let me try and figure that out..would you know whom to get in touch with for cutting it to spec ?

 

[jls001]

Some questions:
1) does stacking platters have sonic benefits? If yes, why?
2) how is ceramic ball superior to a regular steel ball bearing (if at all it is, that is)?

I have been toying with the idea of machining a two inch thick platter of frosted acrylic, exactly of the same diameter as the stock platter of the L75. My calculation says that it will weigh about 4.5 kg. Add 3 kg of the stock platter to get about 7.5 kg platter weight. If I simply machine a new bearing with an extended spindle of about two and half inches, will the stock thrust plate be strong enough to handle the extra weight?

The stock bearing uses steel ball bearing of 5 mm diameter as load bearing member. Will using a ceramic ball of 6.5 mm dia (solely because I have one at hand) increase the load bearing capacity of the bearing assembly? 6.5 mm easily fits into the 9 mm bushing. In fact I'm using it right now instead of the stock 5 mm steel ball.

Will a rounded bottom - instead of the concave one that accommodates the ball bearing - that mates directly with the thrust plate, be an equally good design?

Provided one can get Oilite type brass bushing of a larger diameter than the one in the stock bearing, how does a larger bearing diameter help? I'm asking because almost all premium bearings seem to grow in girth.

Last, but not the least, will Stainless Steel be good enough for large girth bearing? Or does it have to be solely hardened steel?

FWIW, I found a guy who is ready to machine the acrylic platter for nearly reasonable cost. And my favorite lathewalla should be able to machine the bearing. I'm yet to find brass bushing.

Those with more experience may please chirp in with opinions, please. If you think it's a hare brained scheme with no sonic benefits, please feel free to say so.

 

[sachu888]

Hi Joshua,
Yeaterday,I changed my Lenco's bearing oil with SAE32 grade oil.I also replaced steel bearing ball with Ceramic one and original thrust pad with POM.I can clearly feel more flow in music.Its more refined,focused and very detailed without being harsh.This can be because Ceramic ball,thrust pad or oil.The oil(SAE32)I used is thinner than my previous oil.

Regards,
Sachin

 

[anilva]

Some questions:
1) does stacking platters have sonic benefits? If yes, why?
2) how is ceramic ball superior to a regular steel ball bearing (if at all it is, that is)?

I have been toying with the idea of machining a two inch thick platter of frosted acrylic, exactly of the same diameter as the stock platter of the L75. My calculation says that it will weigh about 4.5 kg. Add 3 kg of the stock platter to get about 7.5 kg platter weight. If I simply machine a new bearing with an extended spindle of about two and half inches, will the stock thrust plate be strong enough to handle the extra weight?

The stock bearing uses steel ball bearing of 5 mm diameter as load bearing member. Will using a ceramic ball of 6.5 mm dia (solely because I have one at hand) increase the load bearing capacity of the bearing assembly? 6.5 mm easily fits into the 9 mm bushing. In fact I'm using it right now instead of the stock 5 mm steel ball.

Will a rounded bottom - instead of the concave one that accommodates the ball bearing - that mates directly with the thrust plate, be an equally good design?

Provided one can get Oilite type brass bushing of a larger diameter than the one in the stock bearing, how does a larger bearing diameter help? I'm asking because almost all premium bearings seem to grow in girth.

Last, but not the least, will Stainless Steel be good enough for large girth bearing? Or does it have to be solely hardened steel?

FWIW, I found a guy who is ready to machine the acrylic platter for nearly reasonable cost. And my favorite lathewalla should be able to machine the bearing. I'm yet to find brass bushing.

Those with more experience may please chirp in with opinions, please. If you think it's a hare brained scheme with no sonic benefits, please feel free to say so.

Joshua,

While all of the above might give us a thrill in terms of 'DOING' something to the L75, my view is that the benefits will be marginal compared to a well setup original L75. You may use the spindle extender and try the acrylic platter but I wouldn't change the bearing girth etc. 5mm Ceramic ball bearing might be a good idea purely from load bearing and not from a smoother friction standpoint and associated musical quality.

My two cents.

Cheers.

 

[quad]

And my favorite lathewalla should be able to machine the bearing. I'm yet to find brass bushing.

The normal lathewallas I have seen here cannot do high precision work - at
least not for TT/audiophile kind of tolerances.
Their machines are also old, and i suspect out of tolerance.

 

[prem]

It's a very interesting thing that you mention Anilva. I have always wondered why Lenco did not use a heavy plinth. I am sure they must have experimented. Putting a heavy plinth is one of the easier things to do. So obviously there must have been some reason. Ditto for Garrard too. Maybe your suggestion of restoring the Lenco to its original specs has a lot of merit.

 

[jls001]

Joshua,

While all of the above might give us a thrill in terms of 'DOING' something to the L75, my view is that the benefits will be marginal compared to a well setup original L75. You may use the spindle extender and try the acrylic platter but I wouldn't change the bearing girth etc. 5mm Ceramic ball bearing might be a good idea purely from load bearing and not from a smoother friction standpoint and associated musical quality.

My two cents.

Cheers.

I can think of a theoretical advantage of a heavy platter - the flywheel effect. In fact that's how most modern belt-driven turntables are made - very heavy platter driven by a noiseless DC motor which need not have a high torque (though there are certainly exceptions). The heavy platter gives the turntable extra drive by virtue of the moment of inertia.

The question for us is whether the extra moment of inertia will enhance the already strong drive of the L75. And by how much.

A tight tolerance bearing is supposed to reduce the very minute wobble of the platter when it rotates. The wobble is due to the slacker tolerance of the stock bearing, or due to worn bushing. See the picture with the two red arrows on Thomas Schick's rebuild of an L75. This is a very clever way to check the condition of the bearing. Try the same exercise and see if there is play in your bearing. I guess this trick is applicable not just to L75s. On my L75, there is very minor play, nothing worrisome but you know how things are when some stupid thoughts get into your mind and consume you:lol:

To quote from the above link:
"If there is a little play you will notice. Ideally it shold not move at all. If it does move, the bronze bushings are worn out. That has a weakening influence on the sound. It still sounds nice, but precision or definition is lost."

Emphasis mine.

Better bearings supposedly give you blacker background. A lowered noise floor, that is.

Extended spindle is fairly easy to do as one has to make a replica of the bearing and simply extend the spindle part of the bearing, but my concern was whether the stock 5 mm ball bearing and the stock thrust plate will be able to handle the extra weight. There are now better thrust plates made of POM and PEEK.

Is is true that a ceramic ball bearing will be able to handle more load than a comparable steel ball? Is it also superior in terms of wear and tear resistance, and perhaps have lesser friction?

Why is it that all premium bearings for Garrards, Thorens, and Lencos have much larger diameters than the stock bearing?

Questions, question.

 

[jls001]

The normal lathewallas I have seen here cannot do high precision work - at
least not for TT/audiophile kind of tolerances.
Their machines are also old, and i suspect out of tolerance.

My lathe guy undertakes precision jobs for lots of industrial customers so I am hoping he will be able to achieve the tight tolerances needed. He will need drumming into his head and may be I will have to be actually be present while he does the job. Now, to find appropriate brass bushings.

 

[anilva]

I can think of a theoretical advantage of a heavy platter - the flywheel effect. In fact that's how most modern belt-driven turntables are made - very heavy platter driven by a noiseless DC motor which need not have a high torque (though there are certainly exceptions). The heavy platter gives the turntable extra drive by virtue of the moment of inertia.

The question for us is whether the extra moment of inertia will enhance the already strong drive of the L75. And by how much.

A tight tolerance bearing is supposed to reduce the very minute wobble of the platter when it rotates. The wobble is due to the slacker tolerance of the stock bearing, or due to worn bushing. See the picture with the two red arrows on Thomas Schick's rebuild of an L75. This is a very clever way to check the condition of the bearing. Try the same exercise and see if there is play in your bearing. I guess this trick is applicable not just to L75s. On my L75, there is very minor play, nothing worrisome but you know how things are when some stupid thoughts get into your mind and consume you:lol:

To quote from the above link:
"If there is a little play you will notice. Ideally it shold not move at all. If it does move, the bronze bushings are worn out. That has a weakening influence on the sound. It still sounds nice, but precision or definition is lost."

Emphasis mine.

Better bearings supposedly give you blacker background. A lowered noise floor, that is.

Extended spindle is fairly easy to do as one has to make a replica of the bearing and simply extend the spindle part of the bearing, but my concern was whether the stock 5 mm ball bearing and the stock thrust plate will be able to handle the extra weight. There are now better thrust plates made of POM and PEEK.

Is is true that a ceramic ball bearing will be able to handle more load than a comparable steel ball? Is it also superior in terms of wear and tear resistance, and perhaps have lesser friction?

Why is it that all premium bearings for Garrards, Thorens, and Lencos have much larger diameters than the stock bearing?

Questions, question.

You have some high pedigree turntables already I believe. You can just replace the bearing of the Lenco with another one available on ebay bring it back to spec. They cost about $40. Thomas's Lenco still retains the original plinth and the bearing.

Cheers.

 

[quad]

Now, to find appropriate brass bushings.

Some links you may find useful -

http://www.rgbronze.com/images/material-selection.pdf
Sintered Bronze Plain Bushes
Mumbai bronze bearings

 

[arj]

Some questions:
1) does stacking platters have sonic benefits? If yes, why?
2) how is ceramic ball superior to a regular steel ball bearing (if at all it is, that is)?

I have been toying with the idea of machining a two inch thick platter of frosted acrylic, exactly of the same diameter as the stock platter of the L75. My calculation says that it will weigh about 4.5 kg. Add 3 kg of the stock platter to get about 7.5 kg platter weight. If I simply machine a new bearing with an extended spindle of about two and half inches, will the stock thrust plate be strong enough to handle the extra weight?

The stock bearing uses steel ball bearing of 5 mm diameter as load bearing member. Will using a ceramic ball of 6.5 mm dia (solely because I have one at hand) increase the load bearing capacity of the bearing assembly? 6.5 mm easily fits into the 9 mm bushing. In fact I'm using it right now instead of the stock 5 mm steel ball.

Will a rounded bottom - instead of the concave one that accommodates the ball bearing - that mates directly with the thrust plate, be an equally good design?

Provided one can get Oilite type brass bushing of a larger diameter than the one in the stock bearing, how does a larger bearing diameter help? I'm asking because almost all premium bearings seem to grow in girth.

Last, but not the least, will Stainless Steel be good enough for large girth bearing? Or does it have to be solely hardened steel?

FWIW, I found a guy who is ready to machine the acrylic platter for nearly reasonable cost. And my favorite lathewalla should be able to machine the bearing. I'm yet to find brass bushing.

Those with more experience may please chirp in with opinions, please. If you think it's a hare brained scheme with no sonic benefits, please feel free to say so.

Joshua, I have also thought of a spindle extender/double platter many times but from all i could find out from folks who have done it the results are marginal to say the least.
I also have tried Mirkos stainless steel bearing with a ceramic ball bearing.. while initially it sounded better than the original bearing, when i cleaned/lubed the original bearing and raised the thrust pad slightly with a coin, I found them almost equivalent
but the spindle extender with a acrylic platter is pretty tempting !