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View Full Version : Lenco #2, plinth comparisons, plans etc.



helma
26-07-2017, 13:14
Since I got my 2nd Lenco and my first stock plinth I decided to do some experiments. I know this would be far more fun with some pictures, but I'm lazy with the camera.

One Lenco, two plinths. Big one is 60x40cm, 3 layers of 18mm acacia sandwiched between 18mm layers of Bamboo, so 5 layers in total. Mounting of the turntable with 4 bolts that go through the whole plinth construction. For footers this one has 3 hockey pucks which rest on cradles made of rubberbands & little glass cups. (Think ash-tray feet like I hear DJs of old used to do with SL-1200).

Second plinth is the original one, but with some modifications. Springs were gotten rid of and replaced with small wooden blocks with some furniture rubber footers for a little bit of isolation from the bottom board. I also installed a cross-brace and damped the sides with acrylic mass. Both of these things helped a lot as far as knuckle test for plinth resonances go - it's not as dead obviously as a more substantial plinth, but it doesn't ring anymore and when rapped with knuckles produces a reassuring sounding little thud instead. I've seen several different variations of the stock plinth, this one seems a later production one which is made of chipboard with very thin veneer on top.

I recorded a lead-in groove and analyzed the spectrum for rumble. For first test the top plate was mounted like stock, so the 4 rubber grommets on corners and two screws on the pan. Now these figures don't follow any standard obviously and as such don't hold any meaning compared to anything published anywhere else, but they are comparable (within +/- 2dB or so) between each other. So here they are:

Big plinth
50Hz -59.6dB
100Hz -71.5dB
150Hz -74.1dB

Modified stock plinth
50Hz -59.9dB
100Hz -54.2dB (!!!)
150Hz -75.6dB

That 100Hz was clearly audible, not distracting while listening to music, but between tracks you could hear it, either very faintly or quite clearly depending on the volume :) Very disappointing result for the modified plinth in any case and removing the springs didn't seem to do much for the rumble even with the additional damping of the plinth. Sadly I didn't measure the TT in completely stock form, but using ears alone it was improvement, but a pretty slight one. I traced most of the rumble coming through the idler arm, so I damped it using electrical tape, rotated the rubber grommet 90 degrees just in case and in a different test (not directly comparable to this one, because platter wasn't installed and stylus rested in a resonating hollow plastic cap) that reduced the 100Hz rumble by 6dB and also spread the spectrum a bit. In the above test I doubt the difference would be as great, but probably a few dBs anyway. Next I altered the mounting and got rid of the rubber grommets at corners and the results were as follows:

50Hz -58.2dB
100Hz -64.3dB
150Hz -75.3dB

A whopping 10dB reduction @ 100Hz, which means with the rubber grommets in place (and idler arm undamped), the rumble @ 100Hz was about 3 times as loud. While the modified plinth still falls short of the big one (with better footers) the deck sounds splendid now and is practically silent.

I've heard some people be happy with the stock arrangement with the springs and all, but at least this one didn't sound good at all like that, plus it rumbled. The worst part seemed to be the rubber grommets though. I might try it with the springs yet just for kicks, though the upper plinth that rests on the springs is probably 2-3 kilos heavier now. Based on this, if you want a good sounding Lenco with minimum hassle, just getting rid of the springs and rubber grommets might get you quite far already with the stock plinth. However I noticed at high volumes it was prone to feedback, which doesn't happen at any volume with the big plinth and rubberband cradle footings. I attached two of self-adhesive rubber foam footers into each 4 stock feet on the bottom board and that cured it. I was just curious about what's the minimum effort and money to spend on a Lenco to get good results, and it's also further learning towards the eventual proper plinth.

I plan to try out what more solid mounting does to it - now the top plate is fastened to the plinth with only two puny woodscrews through the pan. I should've installed some additional blocks into the insides to faciliate bolting the deck down, but can't really do that easily anymore. Only easy option is to drill holes into the bottom board and bolt through it, but that means my little isolating rubbers in place of springs would become pretty much meaningless, but seeing they didn't work all that well to begin with, maybe that's not a bad thing.

Now, in stock form I don't think two 50 year old Lencos will perform exactly the same, there have been little variety in production and also the springs and rubber grommets, idler arm rubber grommet etc. have aged differently depending on the life of the deck. If after service the performance is not up to par in stock form, the above modifications cost me about 5 euros in the form of two 310ml tubes of the acrylic mass, and two pieces of scrap wood for the braces. These mods are still more or less reversable if wanting to go back to stock.

I don't know what maintenance (if any) has been done to this new-to-me Lenco, but since it came with a properly mounted Sumiko MMT and no extraneous noise is present I'm assuming at least the main bearing has been cleaned and oiled ... haven't actually opened it up yet, but I can tell it's not running dry. It came with an original 5-hole idler wheel. Just for kicks the results for my first Lenco, for which I've done motor and bearing maintenance and replaced the idler wheel with a Norbert one:

50Hz: -61.4dB
100Hz: -75.3dB
150Hz: -75.1dB

So a little quiter all-in-all, could be many things, probably mostly the idler.

What can be taken away from all this is resonances, the paths they take, damping, coupling/decoupling in mounting and the actual construction of the plinth do matter, not only in perceived sound qualities but in very easily measurable noise levels. Not exactly breaking any new ground here, but I wanted to have some actual numbers for myself to have some reference which is not dependent on my ears and how I happen to feel on a given day.

Btw. my hat off to people who make detailed threads with pics and all for tweaks and modifications they are doing, takes some real effort! I probably spent more time writing down and editing this post than I spent on swapping the Lenco between plinths, recording samples and doing the measurements ...

Next up some thoughts for a new plinth and things I'd like to experiment with.

Jimbo
26-07-2017, 14:14
Interesting Kai. So would you say just removing the rubber grommets you found an improvement or does it make the plinth more likely to pick up airborne vibration?

helma
26-07-2017, 14:46
Interesting Kai. So would you say just removing the rubber grommets you found an improvement or does it make the plinth more likely to pick up airborne vibration?

I think airborne vibration would be a lesser problem than having the top plate resonate with whatever gets through from the motor and idler arm. Removing the grommets was an improvement for both subjective sound quality and measured rumble. Without the grommets the turntable become more prone to acoustic feedback, but this gets into tricky territory because each room is so different and there's so many factors at play from speakers, to placement of turntable, what it is resting on, what kind of flooring you have etc. In my case the TT sits on a (quite resonant) wall shelf because I have very springy wooden floors, and adding some different footers solved the problem. Actually I plan to try how the rubber grommets would work as feet for the plinth, I think they might be ok for that.

I don't think the Lenco engineers were stupid, just that the way the Lenco is stock is a compromise to allow your average Joe to just place the turntable on whatever and get adequate sound without too much sensitivity to foot-falls, feedback etc. - it's same with all the other consumer oriented TTs of the era really, Duals have the top plate sitting on springs, but like the Lenco IMO they are far better off without the springs.

Spectral Morn
26-07-2017, 19:06
:worthless:

Reduced in value, not worthless, with no photos.

Wakefield Turntables
26-07-2017, 20:45
Excellent post, looking forward into incorperating some of your experiments, so its a :popcorn: from me!

helma
26-07-2017, 21:00
Hi Neil, yeah I know :) I'll try to take some when I have the deck in pieces the next time, which should be pretty soon. I should have plenty of time in the coming week or two to fettle with the Lencos - one thing I want to try is a skeletal "two-story" plinth. I was thinking upper bamboo board with cutout for the top plate, then 4 sand filled coke cans or similar between the upper and lower board. If I bolted the whole thing together from the top plate, the lower board could also support the bearing from the bottom. If all goes well, it should have enough mass to deal with vibration, yet provide good damping higher up the frequency range than a typical heavy mass affair. If I understand anything about how damping, vibrations and resonances in a TT plinth work - it's very much possible I don't, but I could always reuse the materials if it doesn't turn out well :)

On the tonearm front, the Sumiko MMT the new Lenco came with was a pleasant surprise, I think it's a very good sounding arm. My only gripe with it is there seems to be some harshness or 'grain' in the upper frequencies and somehow it sounds more like "hifi" overall compared to the Fidelity Research FR-54 on the other Lenco. It might be actually doing some things better than the FR (which really was quite affordable arm in it's day), but there's just some natural and musical rightness to the way that FR-54 behaves that's hard to put into words.

helma
29-07-2017, 13:28
Ok, here's a photo of the original plinth with the mods. The insides are not exactly pretty, but that's not the point :) The acrylic mass doesn't dry completely hard, it's retains a little bit of elasticity. I stuck some leftover pieces of rubber-cork in there as well. The very thin veneer of the plinth was in quite rough shape with many nicks, so I smoothed them out with some filler paste and painted the whole thing black.
20988


Here's a pic of quick test run resting the top plate on 3 cans of well-known soft drink. Two of the cans were filled with sand and one was unopened, to balance out the seismic micro-vibrations and retain good spatial relationship between the stylus / groovewall interface and 3-dimensional rotational forces. Seriously though, I just wanted to try what no plinth does to the sound. The amount of 50Hz rumble doesn't seem to change much with this deck no matter how it is mounted, while 100Hz is very sensitive and shows changes instantly. 100Hz rumble is also a lot more intrusive if there's any coming through. Resting on the coke cans the rumble @ 100Hz was up about 3dB compared to the modified plinth, but still -7dB compared to the same plinth with the rubber grommets in place. It sounded good overall and running the deck this way gives a little bit of a taste of what the deck is capable of, which the original plinth with springs & grommets and all really doesn't IMO (at least not the one I got).
20989

helma
31-07-2017, 20:32
A little trip to Ikea and came away with 2 Lämplig bamboo cutting boards. Wasn't really any cheaper than getting similar 18mm boards cut to size, but they were there ready waiting for me and couldn't resist the call of bamboo.

This is one idea I'm gonna try out, thought the coke cans are a bit too tall to look pleasing aesthetically, but good enough for testing the concept and playing around.
21003


This would be another way, and that center cavity could be filled with all kinds of "stuff" like silicone putty, acrylic mass, peanuts, small rocks and pine cones or whatever, and I like the sleek look. Would have to cut material away from both boards though. Without any cutouts I think the two pieces weigh a little over 6kg total. But if wanting more mass, I could always do the filling thing or get two more of the boards and do a 2nd arrangement like that, either a double decker skeletal thing or just add them to the bottom of the existing plinth. Or add a bottom and top layer of some thin birch ply. Thin because I'd like to cut it so the top plate sits flush with the plinth.
21004

Let's see how this goes, might have something put together tomorrow if the weather permits.

helma
01-08-2017, 20:59
I ditched the sand filled coke can idea for now, initial results were somewhat promising but it was too f' ugly. I opted for a good bit shorter nuts and bolts instead, it's still kinda ugly but this setup now is really tweakable for trying out different things.

How it works the bottom board has nuts glued in the corners and 60mm M10 bolts screwed in, which support the upper board. If you look at the photo you can also see some bolts under the pan - these are not fastened anywhere, but simply have nuts extended so that they provide some upward pressure from the bottom board up to the pan. For now they have some rubber cushions at the top, whether that is a good or bad idea will be seen, but initially it seems better than without the cushions. I ran out of hours, so proper test will have to wait till tomorrow because I had only one long enough M4 threaded rod - the idea is the whole thing is kept together by 4 such rods, mounted into the threaded inserts in the top plate and running through both boards, but currently it's only one and the other 3 short ones just fasten the top plate to the upper board. I also added one wood screw through the hole which originally had the L75 arm rest. It might be even with all 4 threads going through both boards the structure might not be solid enough, but I'll find out tomorrow. I hope it's good enough to see if this kind of build is something I want to commit to, I could still easily revert to a more traditional plinth and I have a feeling a sleek plinth with the center cavity (see previous post pic #2 to see what I'm talking about) filled with some appropriate goo for damping might sound pretty nice.

I did run some little tests with the setup as it is and it could hold promise, but will have to run it everything properly bolted together. Should be wiser tomorrow.

21017

helma
02-08-2017, 15:01
Now the whole thing is stuck together with the 4 threaded rods, M4 rod is quite flexible so it's not a super rigid assembly, though adding tension upward tension from the large bolts helps with that.

Doing some low volume listening and a couple measurements while at it, fiddling with the pan support bolts. There's a definite if somewhat subtle (at least at these volumes I'm currently using) change with / without the bolts. Not sure which I prefer, with added pan support the sound seems to tighten up somewhat, but I also sense there might be a certain harshness somewhere in the midrange perhaps - definitely need more listening. Without the pan supports the sound loosens up some, overall the sound is a bit more relaxed, but not in a bad or imprecise way - more like there's just a better natural and flowing quality to it. But for now I'd be inclined to say the pan supports add "fake precision" ie. colorations in the mid-range (and upper bass perhaps) which initially might make it sound more "tight" but doesn't hold water in longer listening. But that's my initial impression... I need more listening, but am also feeling impatient and might move forward before I get a chance to do that :D

I tried the pan supports with and without rubber cushions between the bolt and top plate and there wasn't much difference to be honest. Measuring it seems without pan support is better (at least the way I'm doing it atm). This is interesting, because screwing / bolting down the pan seems to be the "standard" among tweakers, but so far my ears tell me to let the pan do it's thing without additional support. To be fair the way I'm doing it now is not exactly same as bolting it down. Though I recall talking in person to one Lenco enthusiast who has done many builds, and his opinion was supporting the pan kills the sound. We'll see.

I'm inclined to probably ditch this skeletal thing altogether, glue the two boards together and fill the insides with something viscoelastic, leaning towards the acrylic mass I have used in many other TTs for damping because I'm familiar with it and it seems to do a pretty good job. Unless extended listening convinces me otherwise, but this far nothing suggest this arrangement is better than the plinth of my #1 Lenco which is my reference for now. That arrangement would still make it possible to experiment between bolting/screwing down the pan and not.

helma
02-08-2017, 16:25
Btw. I did some recordings to see the effect of idler arm damping - I previously already had put a pass of electrical tape around the arm, so I added some bits of blu-tack and another round of electrical tape and rumble was further reduced from 1 to 3 dBs - the initial damping had a similar effect, so it does pay off to damp the idler arm (I've seen this one debated). If you have already replinthed and gone over the deck, I don't think damping the idler arm would make for a very obvious improvement since the noise floor should be sufficiently low already, but all the little noises do add up.

I've done some more listening and this skeletal thing seems to work OK, and the way it is now it's already better than the modified stock plinth (but I didn't bolt the deck through the bottom plate for that one). I think I'll move on though, mainly because I'm not sure how to tweak this plinth further without making it uglier (most thing I could do would be very visible) and since I'm not a big fan of the looks to begin with, I'll be happier with something that pleases the eye more.

helma
02-08-2017, 16:39
A photo for good measure, probably the last anyone is gonna see the deck in this configuration :) The placement is very temporary, but desktop speakers were used for listening so acoustic feedback (or feedback through the floor) was not an issue.

I have to say that while it's been interesting and some of my curiosity has been satisfied, I'm also starting to wonder if there really wasn't anything better for me to do today than fool around with this thing. Yet, there's still some hours of daylight left and I could work on the plinth... ugh :)

21022

Wakefield Turntables
02-08-2017, 18:43
Now the whole thing is stuck together with the 4 threaded rods, M4 rod is quite flexible so it's not a super rigid assembly, though adding tension upward tension from the large bolts helps with that.

Doing some low volume listening and a couple measurements while at it, fiddling with the pan support bolts. There's a definite if somewhat subtle (at least at these volumes I'm currently using) change with / without the bolts. Not sure which I prefer, with added pan support the sound seems to tighten up somewhat, but I also sense there might be a certain harshness somewhere in the midrange perhaps - definitely need more listening. Without the pan supports the sound loosens up some, overall the sound is a bit more relaxed, but not in a bad or imprecise way - more like there's just a better natural and flowing quality to it. But for now I'd be inclined to say the pan supports add "fake precision" ie. colorations in the mid-range (and upper bass perhaps) which initially might make it sound more "tight" but doesn't hold water in longer listening. But that's my initial impression... I need more listening, but am also feeling impatient and might move forward before I get a chance to do that :D

I tried the pan supports with and without rubber cushions between the bolt and top plate and there wasn't much difference to be honest. Measuring it seems without pan support is better (at least the way I'm doing it atm). This is interesting, because screwing / bolting down the pan seems to be the "standard" among tweakers, but so far my ears tell me to let the pan do it's thing without additional support. To be fair the way I'm doing it now is not exactly same as bolting it down. Though I recall talking in person to one Lenco enthusiast who has done many builds, and his opinion was supporting the pan kills the sound. We'll see.

I'm inclined to probably ditch this skeletal thing altogether, glue the two boards together and fill the insides with something viscoelastic, leaning towards the acrylic mass I have used in many other TTs for damping because I'm familiar with it and it seems to do a pretty good job. Unless extended listening convinces me otherwise, but this far nothing suggest this arrangement is better than the plinth of my #1 Lenco which is my reference for now. That arrangement would still make it possible to experiment between bolting/screwing down the pan and not.

Perhaps you dont need to bolt the pan down onto your plinth maybe a layer of dampening material or something like EVA (2-3mm) between the pan the plinth (complete surface area) might be more beneficial. I'm planning another plinth design for the latest incarnantion of My Reference Lenco and this is something I'm looking in to.


Btw. I did some recordings to see the effect of idler arm damping - I previously already had put a pass of electrical tape around the arm, so I added some bits of blu-tack and another round of electrical tape and rumble was further reduced from 1 to 3 dBs - the initial damping had a similar effect, so it does pay off to damp the idler arm (I've seen this one debated). If you have already replinthed and gone over the deck, I don't think damping the idler arm would make for a very obvious improvement since the noise floor should be sufficiently low already, but all the little noises do add up.

I've done some more listening and this skeletal thing seems to work OK, and the way it is now it's already better than the modified stock plinth (but I didn't bolt the deck through the bottom plate for that one). I think I'll move on though, mainly because I'm not sure how to tweak this plinth further without making it uglier (most thing I could do would be very visible) and since I'm not a big fan of the looks to begin with, I'll be happier with something that pleases the eye more.

This is another area that I discounted as a possible modification but your mods seem to suggest that it's beneficial. Again something I could try on the new build.

Many thanks for the discussion thread so far, Its been an interesting read so far and a welcome distraction from my own Lenco ramblings. :D

helma
03-08-2017, 13:27
Well, the deck went through a test drive with the two boards simply bolted together with the mounting threads and at least like that it was nowhere as good as the double decker. Had to do a cutout for motor and tonearm on the bottom board of course, so a little less mass (and the bolts I used in the double decker weighed about half a kilo in total as well). Out of necessity feet were also a bit different. Bit too much variables for my liking :) Now the boards are glued together with little bits of wood as support in the cavity area, and 620ml of acrylic mass was used to fill empty cavities. Ran out of the acrylic, it could take another 310ml tube easily. I will give the glue at least some hours to dry under pressure, but I guess later tonight I could do a test drive and see where I'm at.

It would've been interesting experiment to try to find out resonant frequencies for the boards, I guess miking them up for recording and doing some knuckle raps might have done the trick, maybe. I'm starting to come to a conclusion trying to make an effective relatively low mass plinth like this is probably more trial and error than most people are willing to suffer. It's just everything affects everything, but I also think with some clever engineering and better understanding of all the theory involved, it would be possible to make a relatively lightweight plinth which in many ways would out perform a heavy affair. But then again going for the mass is a tried path with good results and anyone can glue pieces of plywood together :) So it's starting to look like it might end up so I'll just keep throwing more mass at this thing until I'm satisfied with the results :D

How you mount the deck to the plinth has an effect, whether you support the pan or not has an effect, how you support the pan has an effect, what you use for feet have an effect, and probably some other things that haven't yet even crossed my mind have an effect on what happens with the energy. And those are only variables that don't even take into account anything about plinth construction, materials, shape, mass etc. etc.

Still, a lot has been learnt already but I'm also starting to get fed up with the experimenting, time to choose a direction and follow it through. I know it won't be a bad sounding TT but it might not be anything like what an optimised Lenco/plinth combination is capable of. Yeah, I'm getting just a tad impatient and perhaps a bit frustrated as well :) Probably the thing to do would be to let this thing sit in bits until I feel like more trial and error, but that's something I have trouble doing, when I start something I need to see it through. I guess I'd rather just finish this and perhaps someday I will cross paths with another Lenco and do another build with more knowledge going in.

helma
04-08-2017, 12:55
Lowered motor voltage from 240V to 220V (which is what it was designed to run), some reduction in vibration that translated into a dB or two of less measurable rumble. I've played with voltages before, as I recall going lower than 200V started to increase vibration again and loss of torque became very obvious. Going from memory anything from about 205 upwards is fine. I wouldn't fuss about the voltage, 240V is good, 220 maybe slightly better overall. But I realized I have a spare 220 -> 110 step-down transformer, so I'm gonna try the motor wired for 110V because the word on the street seems to be this lowers vibration by quite a lot because the coils are wired in parallel instead of series. I'll just need to find a US mains plug or travel adapter somewhere...

Wakefield Turntables
04-08-2017, 14:03
Lowered motor voltage from 240V to 220V (which is what it was designed to run), some reduction in vibration that translated into a dB or two of less measurable rumble. I've played with voltages before, as I recall going lower than 200V started to increase vibration again and loss of torque became very obvious. Going from memory anything from about 205 upwards is fine. I wouldn't fuss about the voltage, 240V is good, 220 maybe slightly better overall. But I realized I have a spare 220 -> 110 step-down transformer, so I'm gonna try the motor wired for 110V because the word on the street seems to be this lowers vibration by quite a lot because the coils are wired in parallel instead of series. I'll just need to find a US mains plug or travel adapter somewhere...

Your findings seem to mirror my own. I've messed around with lower voltages and came to the conclusion 220V was best for my ears. I've also been planning the 110V motor rewire but just havent had time so I'm really looking forward to seeing how this turns out.

helma
05-08-2017, 17:51
I've got a 45W rated transformer sitting unused and a cheap travel adaptor should arrive here sometime next week. The rewire for 110V is as easy as loosening a couple screws and moving two wires around.

I managed to squeeze 3 more tubes of the acryl stuff inside the middle layer of the plinth, also added some support pieces of wood so the top layer can't flex. It was an improvement of about 2-3dB but at least in terms of measurements my new plinth still falls a bit short of the first one in terms of noise from the deck. It probably just doesn't have enough mass to be as effective in making motor vibrations "disappear" as the bigger plinth. Based on my experiments with this one, I really lucked out with the first plinth with some of the design choices I made by just winging it and going by gut feel. This new Lenco is gonna be one sleek looking mofo though :D I really like the proportions of a thin plinth with the deck positioned just right. Haven't yet done much real listening which will be the final judge of course.

I also experimented with supporting the pan again, this time around I actually managed to make it measure as good and even slightly better than without the supports, but I'm still not convinced by the sound. On a quick listen it sounds to me like bass is perhaps a bit more taut and controlled, but somewhere higher up things sound a bit 'strained'. I've yet to reach a conclusion if this is just a more accurate and drier presentation (and perhaps highlighting a setup issue like VTA or something) or somekind of resonance. Will need more listening and I think I'll try adding even more support to see what direction that takes things. I have to say I'm a bit disappointed because I secretly hoped for supporting the pan to be some kind of magic bullet since it seems such an universally accepted improvement. It was something I hadn't tried because the plinth of my first Lenco would make experiments difficult - the cutouts were originally for a Connoisseur BD-2 and I just enlargened them at appropriate places and stuffed the empty places with all sorts of "stuff", mainly the aforementioned acryl mass and some rubbercork mat for 'coating', not really leaving any surfaces that would work easily for pan support.

It seems to me for minimal amount of mass a double decker configuration is very effective and yields better results more easily, not sure why but some sort of magic damping must be going on :)

I also bought a can of Maston "Rubber Comp" which is a rubber coating spray, I guess similar to something called PlastiDip which seems to be popular in some parts of the world. The can suggests 4 layers 15 minutes between each layer and the final coating should be easy to peel of if you desire to get rid of it. I plan to try it on the platter at least and see if it makes a difference for better or worse. Should be easily reversible if the stuff works as advertised...

helma
07-08-2017, 14:03
Well I tried the rubber spray on the platter, only two coats though because I didn't want to over do it and well, it had next to no effect on ringing of the platter. Interesting looking finish though. I opened up the main bearing finally, was going to check / change the thrust plate, but it seemed previous owner had already been there, changed the thrust plate to a metal one and sealed the bottom plastic plug so tight with something I couldn't even get it off :) Since the bearing always was very silent and felt good in use, I just changed the oil. The bearing is definitely better than on my first Lenco, everything looks and feels very smooth and tight. I used some pretty light oil which seems pretty much identical in viscosity and color as the one that was there previously and platter takes over 5 minutes to spin to a halt from 33rpm. Seeing this example certainly made me think higher of the stock bearing. It is sort of small diameter and skimpy for such a heavy platter, but machining tolerances on this one at least seem as tight as any vintage TT I've come upon, as far as you can judge by feel and eyeballing (which might not be very far...)

Run into some trouble with finished the plinth, I was putting too much faith on the wood filler I'm using to get the front cavity even with the bottom and top layers, so it has kept collapsing and I've had to add more and more of it... I think I'm on my 4th fill now, but it looks like this one might finally do it. I could always craft a piece of veneer or something for the front, let's see how this turns out. I have to admit I'm not big on fine details and don't mind some DIY look and feel on my turntables as long as the basics of the aestethics are right. Fine for me, but if I ever decide to sell either of my Lencos (don't think I will though) it'll probably come bite me because on both all the fine detail on finishing, top plate paint etc. are really half-assed to put it bluntly. Oh well :)

Can't wait to get the plinth to a stage where I can put everything back together again, wanna see how it all looks now and get spinning some tunes.

helma
16-08-2017, 11:47
Life got in the way and I had to take a week off from the Lenco :) Got back to it yesterday, I've had some trouble with the woodworking and finishing side of things, part of it because of not taking enough time to do things properly, part of it because of somewhat loose tolerances and sloppy construction of the Ikea chopping boards and mostly because of doing all the tests and trying different things meant it just wasn't possible to know what exactly I was going to do when starting out. Got that sorted now except for final touches to make it look right.

I rewired the motor for 110V, can't say anything completely conclusive about it because between running the deck at 220V and rewiring it I also filled the old tonearm hole in the top plate and that is bound to have some slight effect on vibration damping characteristics I believe. However it does seem it vibrates a bit less and in terms of measurable rumble it's maybe another dB or two down, except for the peak I get at 23Hz which went down by a whopping 8dB or so. But this is something that is also greatly affected by all sorts of things like how tightly the top plate is bolted down to the plinth, how the pan is supported or not etc. so some of it might be just that the bolts and screws I have holding the thing to the plinth are fastened with somewhat different torque than before. Still, it seems like a worthy tweak but I wouldn't deem it a really necessary one - it's probably about similar in effect to dropping the voltage from ̃240V to 220V or so - now I'm running the motor with some series resistors at about 107V which is better than the 115V or so I get from the step down alone.

In putting things back together I ran into a weird issue with bearing and it seems I have to find a way to take that very tightly sealed (by previous owner) bottom plug off after all, it might be I have to just break it and use something else as a cap or seal the bottom with some candlewax or something. Like I mentioned in my previous post after cleaning and reoiling the bearing the spin down time was something like 5½ minutes - but now it's only 30 seconds! I cleaned and oiled it again but no change, even removed the side screw just in case, have made sure the platter doesn't rub into anything on the top plate but to no avail. The puzzling thing is spinning the bearing without platter it feels very smooth and free, so my suspicion is something is happening at the thrust pad / ball bearing interface under load. It doesn't make any noise and is still very silent in use, but this needs to be investigated and sorted out because running the bearing like this can't be good. From 5½ minutes to ½ a minute just isn't right. I have a spare POM thrust pad identical to the one I've been using in the other Lenco with good success. I guess the oil I used could be another suspect, but I've used the very same oil in about every turntable bearing I've ever had and never had a problem before. In the other Lenco I'm using 5W/30 syntetic motor oil though, mainly because that bearing is just a tad looser than some other and for it the motor oil seemed a good choice because it's a bit thicker than the very runny stuff I've used in most bearings.

helma
16-08-2017, 12:26
Well that was pretty fast in the end, some big pliers did the trick for removing the bottom cap. Still no clue what was wrong and the trust pad seemed fine - maybe it just wasn't somehow properly seated or something, in any case I added the POM plate on top of the existing metal one (which was in some fashion glued to the bottom support cap) and we're back to healthy spin down times, 2-3 minutes, which seems about right for these POM plates. The metal plate looked quite nice, I wonder where it was sourced from and when all was just right the bearing was crazy free running, so I might revisit this at some later date.