Building a Plinth for Lenco L75

Joshua,
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Achates Idler Drive Modular Inverted Bearing Debut | Turntables | Hammond, Indiana 46324 | AudiogoN - The High-end Audio Community

Inverted bearing on a lenco base

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Here's a pic from when this turntable was with its original owner, Ranjeet Singh

Two 3012s and an an Ortofon 12 incher. One 3012 is now with Malvai, the second one with me:) and I guess the Ortofon remains with Mr Singh.
 
Two 3012s and an an Ortofon 12 incher. One 3012 is now with Malvai, the second one with me:) and I guess the Ortofon remains with Mr Singh.

From your experience with customization, what is your opinion on the method used for mounting the additional tonearms? He has not used the traditional arm pod approach. Apologies for a bit of a thread-hijack but could not resist asking.
 
From your experience with customization, what is your opinion on the method used for mounting the additional tonearms? He has not used the traditional arm pod approach. Apologies for a bit of a thread-hijack but could not resist asking.

It is quite an unique approach to tonearm mounting. It will work because the arm baord is rigid copper plates. But in my opinion, it is a convoluted method of arriving from point A to B, via may be C and D.
 
It's been a few days now so I changed lube. The old lube has become greyish. The thrust plate has developed a tiny indentation where the bearing ball rests.

Right now, whatever record I play sounds distorted and crappy. May be that's part of the wear-in? The distortion sounds similar to IGD but occurs from the outermost track itself on tracks I know play very clean. Will have to bide by my time till this phase passes.
 
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I got an inkling of what may be wrong (subject to verification) - I think I am faced with a "torque deficit".

Last night, I was using an antistatic record brush to clean a record that was kept spinning on the Lenco L75. The weight of the brush actually caused the platter to slow down and nearly stop it. I am seeing this for the first time on the Lenco L75. It has immense torque and is never bothered by the mere weight of a record cleaning brush.

So there is either a new source of friction introduced post change of lube (here's hoping I haven't ruined the mating parts:sad:), or the current lube concoction is too viscous. The latter is the less likely scenario, but can be easily proven by flushing the current lube and replacing it with regular sewing machine oil only to lube both the spindle and bearing ball. So this calls for some more grease elbow (literally) this weekend.

FWIW, I re-aligned the nulls and adjusted overhang. Not much improvement. Tracking force is 1.93 grams (recommended is 1.9g).
 
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It's all sweetness and light again in Lencoland:)

All traces of grease removed. Now using only sewing machine oil to lube the spindle. Also, the threaded bottom (thrust plate) was leaking oil so I used liberal amounts of plumber's white tape (teflon tape) to seal it.

It now passes the antistatic brush test with flying colours.

But an irritating side effect has become apparent - not so loud ticks and surface noise has become more audible, probably because the bearing has lowered the noise floor. A good thing, but a bad thing too.
 
Are you sure your alignment is perfect? Ticks and surface noise could be due to mis-alignment in my opinion and cannot be due to lower noise floor. I think you should try several records before confirming the root cause of higher surface noise
 
Are you sure your alignment is perfect? Ticks and surface noise could be due to mis-alignment in my opinion and cannot be due to lower noise floor. I think you should try several records before confirming the root cause of higher surface noise

My alignment is still a bit off - I can hear IGD. I guess I re-aligned it under stress, and need to refine it further. BTW, I use several records as reference, more because I like the music and less because they're "audiophile" in the quality of the recording (though some do qualify on that count). I listen to these records a lot, and use them for testing any new component in the analog chain.They're not in pristine condition but they never used to have that much surface noise or ticks. At least not enough to annoy me. IMHO, improper alignment will produce distortion, but I am not sure if it would accentuate surface noise and ticks.
 
Fun experiment:

Measurement of vibration taken with an Android phone running Vibrometer app available free from the Play Store. This one is taken on top of the plinth, phone placed near the Lenco L75 On-Off switch.



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And this one was taken on top of the plinth near the motor.


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Track used was bass heavy and complex. Played at normal listening volume. Sampled over about a minute each.


I took the same measurement on the concrete floor and the mean is similar to the measurements above.


And this one is taken atop my right speaker. Track was Frankie Goes to Hollywood's Two Tribes (surrender)


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Please try this at home and report back your results. I believe there is a similar app for iPhones too.
 
I have been reading up on bearing oils for Lencos here and there seems to be no consensus on which oil is best. However, there are a couple of consensus:

1) use synthetic oil
2) thicker oil sounds better, though there is no consensus on what is the best viscosity (5W weight oil seems to be preferred viscosity but I don't know where one can get single weight oil - range type oils like 5W30 is what we usually find in shops).

There are lots of folks who have tried synthetic motor oil like Mobil 1 of 5W30 grade, while others are happy with synthetic compressor oil. Some others use grease on the load bearing part and 3-in-1 oil (sewing machine oil) for the sidewalls of the spindle.

My take home from all this clutter: use any decent synthetic oil, try viscosity to suit one's taste because different viscosity does change the way a turntable sounds.

With that put aside, last night I started using the compressor oil that I bought. This is a "blind" use as I don't know its viscocity rating, nor whether it is synthetic or natural (my guess is it is natural because manufacturer's usually don't forget to trumpet about the virtues of synthetic!). This oil is much thicker than the sewing machine oil that I have been using. I drained off the sewing machine oil and cleaned it thoroughly, then poured the new oil. Later I daubed/smeared the spindle liberally with the compressor oil and carefully inserted it. Being thicker, it takes quite some time for the spindle to settle to its final resting position. It was impossible to push the spindle to its final position. The air trapped at the bottom just pushed it back. So I put the platter on and let it spin for a few minutes for the spindle to finally settle.

Listening to oil:
This is a new and interesting occupation for tuntablephiles :lol: - listening to different oils. The sound was straightaway more solid and darker that what I had heard with the sewing machine oil. It gained more focus. It also tamed the ticks and pops, and I am back to hearing the same level of ticks and pops that I used to hear before. This bearing has a lower noise floor than the stock bearing. This translates to a bit more micro details being audible in the music. But as already mentioned, it has its downside too by making you hear the ticks and pops in the records. This was with Sewing machine oil lube. My guess is the thicker and more viscous compressor oil provides some sort of damping that somehow better suppresses the ticks and pops. But I don't know if, on the other hand, it is overdamped and losing the agility to react to fast transients and perhaps causing more lethargic decays. I thought I heard a wee bit more lethargic bass.

I will listen to this oil till I can lay my hands on some more synthetic motor oil.
 
A block of acrylic being cut:

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To ease the process of rounding it, the block is "hexagonised":


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This is how the final product looks like, stacked on the stock platter. The edge is buffed to a shine (as are the flat surfaces):


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Now, there's just one SNAFU - the spindle for the stacked platter is extra long - 2 inches + 1 inch extra. When stacked on top of the aluminium platter, the acrylic platter wobbles, as though it is spinning a warped record. I think the 3 inch long spindle is not correctly machined. The other thing that can go wrong is spindle hole bored out of alignment (should be exactly perpendicular to the surface of the platter). It does look like the former.

Specs:
1) thickness: 50 mm
2) diameter: 317 mm
3) weight: not measured, but should be around 4.5 kgs as per my calculation

I initially tried it by placing it directly on top of the aluminium platter and it works fine. However, the tonearm VTA was drooping slightly towards the cartridge end, so I placed a felt mat between the platters to compensate. I can't hear a difference between the two, though. Mat used is acrylic, 4 mm thick.
 
I did some observations today. I substituted the acrylic platter with an equally thick one composed of a platter from a Garrard 301 and a few acrylic mats and felt mats. It drastically reduced the wobble but not fully. This means that the thick acrylic platter has uneven thickness. I measured the thickness at various points on the periphery and it varied from 47.xx mm to 49.xx mm. So this seems to be introduced at the buffing stage.

The temporary composite platter mentioned above is also not perfect and shows slight wobble. This means the spindle isn't perfect, though it's close. The composite platter sounds dark and has rolled off highs. Too much energy is absorbed, so it's no good. On the other hand, the thick acrylic sounds somewhat darker than the stock platter alone, but gains more density and focus. It retains its liveliness, while adding gravitas in the lower octaves. I don't know if that makes sense
 
Excellent work Joshua. Turntable bearing and platter looks superb. Regarding wobble how was the platter held on lathe and how was the center hole made ? Once put on lathe it should be finalized on lathe itself. Would give more accuracy. Also longer the bearing spindle more accuracy is required a slight variation at the end would magnify wobble.
Regarding lubricants, one theory of viscous lubricant is; 'if' motor plus idler has sufficient torque it overrides the dynamically changing stylus drag because motor is already working on little heavier resistive force of the viscous lubricant when in motion.
You have achieved admirable high quality DIY, so kudos to the work well done. :thumbsup:
Regards
 
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