Lenco L75 based Turntable Project

[Qwin]

Lenco Based Turntable Project

I've heard some great idler drive turntables over the years and always wanted to try one myself. The likes of Garrard and Thorens have got to very high prices recently and more than I wanted to spend. I came across various articles singing the praises of the Lenco L75 (GL75 in UK) and after some research over at the Lenco Heaven website, I decided this model would be a good way into the world of idler drives.

This was the donor deck I purchased off eBay, no arm and a rough looking plinth, but fully working.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_00.jpg




I built a new plinth from three 40mm slabs of Bamboo worktop. My purchased material is A1 quality, with no voids or filler, but expensive. I found a kitchen supplier selling A2 offcuts at reasonable price, I think these were the cut outs for double basin sinks etc, so scrap.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_02T.jpg




I used the PTP6 stainless steel top plates available from the Netherlands and an upgrade bearing made by SPH (Malaysia), I built an additional bottom bracket to support the bearing both ends.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_01.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_02K2.jpg




With a good bearing, these heavy platter decks can take over a minute to come to rest when the motor is turned off. This can be a pain when changing records, so I designed/built a brake, which brings the platter to rest in less than one revolution.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_02R.jpg



I added a spirit bubble and feet, adjustable from the top face, to make it easy to set up and finished the deck in Satin varnish.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_02V.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_04.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_04B.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_05.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_06.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_07.jpg

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_09.jpg


Tonearm

Similar to my hankering for an idler drive, I've always wanted to try the original Mission 774 tonearm and I managed to obtain a very nice example from a member of this parish. Just like this:

https://www.jkwynn.co.uk//774/Pics/774_01.jpg




Anyone who has followed my projects knows I like to do things my own way, so modifications were bound to happen. The arm is very well engineered, so no fear of me touching anything that would upset that. However, the base plate has no way of adjusting the Spindle to Pivot distance and the method of holding the arm stub, in a relatively thin plate, with a single grub screw is not the best, so I made my own base for the arm to drop into.

https://www.jkwynn.co.uk//774/Pics/774_13.jpg

https://www.jkwynn.co.uk//774/Pics/774_14.jpg

https://www.jkwynn.co.uk//774/Pics/774_15.jpg



I rewired the arm with “The Missing Link” and my cartridge of choice was the Van Den Hul ONE Special. This is a good compliance match for the arm and the cartridge has a healthy current output, important for my fully balanced current amplifying AQVOX 2Ci phono stage.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_12.jpg




Fitting the arm was not without its problems.
There is conflicting and confusing information on the internet regarding the set up for this arm, some of it from Missions own documentation. The only dimension I could trust, was the effective length of 229mm which is in the specification info that comes with the arm. I set out with this in mind and using the other dimensions for offset and S to P being quoted on the net. This was the result.

https://www.jkwynn.co.uk//774/Pics/774_15B.jpg




As you can see, the cartridge leads exit the arm wand under the holding clamp. If it were tightened in this position it would trap and probably damage the wires.
Something is seriously wrong here, the effective length seems about 10mm to short for my wand. I was confident it was the original Mission badged wand that came with the arm. Made with a double wall tube, most replacement wands are single wall. With all the conflicting information I decided to create my own geometry, using the alignment program on vinyl engine.

First step was to measure the offset angle of the mounting block on my specific arm wand, as there was a variety of dimensions being talked about on various forums, from 20.5deg to 22deg. I created a measuring template, which other owners might find useful and is linked here:
https://www.jkwynn.co.uk//774/Pics/Lenco_04_Offset_Angle.pdf

My mounting block has a measured offset of 21deg, so this would be locked into the settings of the alignment program as a non variable and the Spindle to Pivot and effective length, which are adjustable, would be tweaked in the program. The following results and comparison with the presumed Mission, Lofgren A and Stevenson geometry were produced.


https://www.jkwynn.co.uk//774/Pics/774_22.jpg


https://www.jkwynn.co.uk//774/Pics/774_23.jpg


https://www.jkwynn.co.uk//774/Pics/774_24.jpg

As can be seen my Geometry seems to have better results than the presumed Mission dimensions, in terms of tracking error and distortion. The cartridge sits square in the mounting block and the wires now exit the wand in front of the clamp, like this:

https://www.jkwynn.co.uk//774/Pics/774_15C.jpg




It's early days, I used a basic set up, with the stylus pressure in the middle of the range, Azimuth and VTA were handled with a spirit bubble on the mounting block, so I haven't dialled in the sweet spot or tried the paddles/damping oil, but it all sounds very nice regardless. A very black background and lack of surface noise (on a good record) tends to suggest the alignment is a good one.

My wand is 247mm long, measured along its centre line, to the middle of the front face of the cartridge mounting block. Should anyone else have the same issues I faced, with a wand of similar length and offset, you might want to try my alignment. The only down side, is my S to P distance has increased by 9.6mm, not a problem for my adjustable base, but the stock base will need re-mounting at the new distance. The values are:

Spindle to Pivot = 225mm
Effective Length = 239.5mm
Offset Angle = 21deg

The protractor I created can be found here: https://www.jkwynn.co.uk//774/Pics/Lenco_05_Protractor.pdf



I'm just enjoying the way this combination of turntable arm and cartridge work together.

https://www.jkwynn.co.uk/Lenco/Pics/Lenco_4_14.jpg

If you want a blow by blow account of the plinth build or arm mods/alignment, find the Project on my web site here: https://www.jkwynn.co.uk/Lenco/Lenco_Thumbs.html

[walpurgis]

Looking very good Ken. I can see a lot of thought and care has gone into everything :thumbsup:.

[Ali Tait]

Yes indeed, look forward to hearing it.

[Qwin]

Thanks Geoff, Ali
The last deck I'll build, so ease of set up and use was a high priority.

Need to thin out my Turntables now.
My Techie/ProJect hybrid with Terminator arm may have to go.
As will the Techie with Rega arm.
Just don't have the space since I moved to Carlisle.

[Barry]

Excellent write up Ken. :) Greatly admire your new arm base and height adjustment attachment. Well done!

The Van den Hul One Special is a very good cartridge. I use one in a Breuer Dynamic 5A arm.

All tonearm alignment prescriptions are a compromise, and often the manufacturer's instructions seem to conflict with what is found in practice; the instructions for the Breuer arm are certainly confusing: https://theartofsound.net/forum/showthread.php?31118-The-Breuer-Dynamic-Type-5A-pickup-arm. I ignored them and set it up to correspond to Baerwald (Lofgren 'A'), and it sounds perfect to my ears.

[Qwin]

Thanks Barry, I have no milling facilities, so the base was made by hand with a hacksaw, drill and files.
Yes its amazing how many of these old arms seem to conflict with the instructions that came with them.
A friend has a Grace G-707 and he can't get it to work with the supplied template, the slots in the head shell just aren't long enough to align the stylus. He still gets it to sound good though, using trial and error.

The Silicon fluid for the damping trough arrived today, I had no idea it was so thick and gloopy, I thought it would be like thick oil, but its more like treacle (30k and 50k cSt).

[Barry]

Apropos the viscosity, in general for pickup arms the following apply:

100,000cSt for unipivots

30,000cSt for damping troughs

20,000cSt for lift/lower devices.

So your fluid at beween 30k and 50k cSt sounds about right. Do you have an assortment of paddles to use with the damping trough? With the SME version, they provide three paddles of various sizes. I have found that the smallest one is quite sufficient, but then the damping fluid supplied by SME is 200,000cSt (!)

One can always thin or dilute the silicon fluid, but the thinners are not very pleasant (acetone, naptha, toluene, etc) and may be difficult to obtain. If you can't get hold of acetone, try nail polish remover. Alcohol (isopropanol) is probably the safest and easiest solution (no pun intended), but I haven't tried it.

[Qwin]

Thanks for that information Barry, very useful.

The 774 comes with three paddles, I have the large and med size, the med looks to be the one for my cartridge compliance, based on the chart in the arms manual.

I have the dimensions for all three paddles and posted these on my web site, the smallest can easily be made from 18swg (1.22mm) stainless wire using pliers. Plus there is a guy on eBay selling new sets of three.
I will try the med paddle and 30,000cSt first and see how that works out.

200,000cSt ! that's a solid :D

[walpurgis]

I'd generally start with the smallest paddle, especially if the silicone damping fluid is thick. You'll need to experiment depending on cartridge used, some cartridges need no damping. If you want, you can thin the fluid with silicone oil, the type sold in aerosols as a general lubricant.

[Patrick Dixon]

It looks very nice. Always good to get a plumbing fitting into a build too ;->

I have two Mission 774 arms, an early type (purchased Dec 79) and a later type. AFAIR (I can't find the earlier one ATM) they both have the same headshell offset.

The later one (which I have mounted on a Thorens TD124 II with a Decca SC4E) has the arm wiring exiting the tube around 30mm from the end and it's aligned so that there is about 8mm of arm tube protruding behind the clamp. The original template says the spindle to mounting position is 8 9/16" (217.5mm) and the original alignment protractor has the null point at 61mm. I can't recall what I set mine up to, but it sounds OK to me.

[Qwin]

It looks very nice. Always good to get a plumbing fitting into a build too ;->

I have two Mission 774 arms, an early type (purchased Dec 79) and a later type. AFAIR (I can't find the earlier one ATM) they both have the same headshell offset.

The later one (which I have mounted on a Thorens TD124 II with a Decca SC4E) has the arm wiring exiting the tube around 30mm from the end and it's aligned so that there is about 8mm of arm tube protruding behind the clamp. The original template says the spindle to mounting position is 8 9/16" (217.5mm) and the original alignment protractor has the null point at 61mm. I can't recall what I set mine up to, but it sounds OK to me.

Yeh, that's different to my wand, exit hole for wires is less than 20mm on mine, this is why my wires end up under the clamp with stock eff Lgth, my clamp is also the wider type (they altered it).
You are confirming what I already thought.
The template might say 217.5 but the diagram in the manual says 215.4, its a mess.
215.4/217.5 the wires are still under the clamp on mine. I increased eff lgth nearly 10mm to clear the clamp.
So many undocumented changes on many of these old arms, not just Mission.
For the parts I have, my geometry seems to work very well, but I am well aware it may not suit all variants.

Yes, I like to plumb it in! The arm stub is 15.6mm dia, water fittings are 15.2mm dia to take a 15mm tube. I used an adjustable reamer to enlarge the fitting, till it was a sliding fit on the arm stub.

[Patrick Dixon]

my clamp is also the wider type (they altered it).


Yes, my early 1979 one has the shorter clamp. The earlier one is slightly trickier to set up with the damping trough from what I remember (I think the trough is slightly shorter too) - from memory I think the paddle can hit the end before end of side if you don't get it quite right, and you might need to have the arm at rest slightly not perpendicular to the plinth front edge to achieve that.

I have found my other arm wand now and it's the same length but has the wire exit about 19mm from the tube end (as yours is). This is the 1979 arm which I bought from the original owner. The manual for that arm has a correction stuck over the contents page and over the paddles section on the third page, and it also has the 8.48" / 215.4mm dimension on the diagram on page 2. The manual for the later arm has the pages reprinted with the corrections, and no 215.4 dimension on the diagram (there is a separate template). So I think you have a later base and pivot section and an earlier manual and wand.

(You can actually see the different trough casting shapes in the manuals - and maybe the clamp position is slightly further back?).

https://theartofsound.net/forum/attachment.php?attachmentid=30514&d=1661706735

But anyway, you seem to have an effective and theoretically sound solution and a very nice looking deck, so I'm sure you are not going to loose any sleep over it! But it would be nice to get to the bottom of what Mission intended.


30514

[Qwin]

Yes, I agree, if not for our sake, more for anyone purchasing one from scratch, not knowing any of these anomalies.

[karma1967]

more confusion as the manual states 215.4 spindle to pivot.
great work though ken!

[Patrick Dixon]

more confusion as the manual states 215.4 spindle to pivot.

It depends which version of the manual ... the later one doesn't.

Having played around with the calculator, I think the 229mm effective length is wrong (or they mean something other than spindle to pivot + overhang). The 'Mission Alignment Protractor' I have has the null point at 61mm so for a 20.5deg offset (if that's what it is) and 217.5mm pivot to spindle (as per the 'Mission 774 Installation Template' I also have) that would give an overhang of 13.75mm. I think this is what you'd end up with if you set the arm up using their templates (it may even be how mine is set!).

It will give you 229mm if you set spindle to pivot 215.4mm and null point at 61mm (overhang 13.6mm)

[Ali Tait]

I read somewhere to fill the silicone so that it just touches the bottom of the paddle you’re using. YMMV of course, they stated it would kill the sound if it was filled up. I have mine like this.

[drSM]

Ken has given every facet of the build his attention to perfection.
I ve had a front row seat, almost, with Ken's build.
I hope he wont mind me hijacking this thread.
In fact i did a parallel build here in KL Malaysia after i relieved my cousin of her late father's L75 telling her it was far too much trouble to sort out.
My search for suitable bamboo failed. But recycled ply from crate for Finnish mini CT scanner has done it for me.
I used 12 layers to make an 11 cm thick plinth.
Ken got me in touch with Sien who lives in the same city.
For this build I used his plates (so mine is not a PTP), main bearing and an asymmetric mount for arm base (to get S2P spot on).
Jelco 850S. and i ve been using a Denon 103R and Ortofon MC15 Super II both restylied .
I have a 5mm acrylic mat and O rings like Ken's to dampen the platter, but i decided against Sien's Cu mat
My motor was serviced by Sien but its still quite noisy, and there s a clicky sound that Lencoheads here conclude is from the idler.
Oddly very little of that is transmitted to the speakers .
This tt produces a very engaging sound with plenty PRAT30515305163051730518
Feet are from Michael Lim of Rega upgrade fame(also a local chap)
Really pleased with this Malaysian L75 rebuild.
I ve secured another motor and will look into a new idler and that should do it.
Thanks Ken for all help.

[Qwin]

I read somewhere to fill the silicone so that it just touches the bottom of the paddle you’re using. YMMV of course, they stated it would kill the sound if it was filled up. I have mine like this.

I think it depends on the paddle size and viscosity used Ali.

Yesterday, I tried the med paddle and 30k cSt fluid, with the trough half full and it made very little difference, to being run dry.
Maybe the slightest improvement to the crispness (leading/trailing edges) of vocals.

[Qwin]

It depends which version of the manual ... the later one doesn't.

Having played around with the calculator, I think the 229mm effective length is wrong (or they mean something other than spindle to pivot + overhang). The 'Mission Alignment Protractor' I have has the null point at 61mm so for a 20.5deg offset (if that's what it is) and 217.5mm pivot to spindle (as per the 'Mission 774 Installation Template' I also have) that would give an overhang of 13.75mm. I think this is what you'd end up with if you set the arm up using their templates (it may even be how mine is set!).

It will give you 229mm if you set spindle to pivot 215.4mm and null point at 61mm (overhang 13.6mm)

I think your conclusions mirror mine Patrick, I had serious doubts about the geometry being proposed as the correct Mission values.
This was mainly because it plotted fairly poor results on the Vinyl Engine program and others. If you check the chart values and plots in my opening post, you will see my own geometry compares very favourably against the supposed Mission. Mission in Orange mine in Blue in the Plots. The distortion and error values are much lower for mine.

[walpurgis]

The usual improvements heard with fluid damping are in the bass, which may sound tighter and more weighty. This can be more evident with Deccas and low compliance MCs.

[Qwin]

My motor was serviced by Sien but its still quite noisy, and there s a clicky sound that Lencoheads here conclude is from the idler.
Oddly very little of that is transmitted to the speakers .
This tt produces a very engaging sound with plenty PRAT30515305163051730518
Feet are from Michael Lim of Rega upgrade fame(also a local chap)
Really pleased with this Malaysian L75 rebuild.
I ve secured another motor and will look into a new idler and that should do it.
Thanks Ken for all help.

Your welcome Shahrin, hope you get that noise issue sorted.
For those not in the know, Sien is the proprietor of SPH in Malaysia and he makes various upgrade parts for Lenco and other TT's, complete TT's and his own arms.

[Qwin]

The usual improvements heard with fluid damping are in the bass, which may sound tighter and more weighty. This can be more evident with Deccas and low compliance MCs.

Noted Geoff, thanks for that.

[Qwin]

https://theartofsound.net/forum/attachment.php?attachmentid=30514&d=1661706735
30514

Thanks for posting that picture Patrick.

If you compare the earlier assembly (lower pic) with the later one above. The wires exit the arm, much closer to the end of the wand on the earlier one.

What I seem to have, is the early base plate and wand, with the later bearing housing, containing the bigger trough and wider clamp.

It all makes sense now.

:thumbsup:

[karma1967]

ah mystery solved!

[Patrick Dixon]

Both the arm wands I have (old and newer) have the same headshell offset (whatever it is), so I'm not sure where the other offsets that people have reported come in.

I am not sure if you have the older clamp whether the arm wand is long enough to achieve your revised geometry.

[Qwin]

Both the arm wands I have (old and newer) have the same headshell offset (whatever it is), so I'm not sure where the other offsets that people have reported come in.

I am not sure if you have the older clamp whether the arm wand is long enough to achieve your revised geometry.

I don't think the earlier version will work either, the wand will be to far into the narrow clamp to grip it effectively. I've pointed that out in my full project on my website, but thanks for pointing it out here. The later product will work fine with my geometry, even a later wand in an early body should work, it's just a genuine early version, with the correct parts that wont work.

[Qwin]

Didn't like the idea of having to polish the Copper mat regularly, its a messy job, Copper tarnishes quickly and every finger mark will go Black in a short time.
I thought of painting it with clear lacquer, Black etch primer or even Flocking it, but was worried about what it would do to the sound, as the bare Copper works very well.
I ended up oxidizing the surface with some jewellers patina fluid for that aged Copper look.
It's not a perfectly even colour, but much more even than just leaving it to oxidize naturally, I quite like it.
This should protect it and be a fit and forget finish that doesn't effect the sound quality.

https://www.jkwynn.co.uk//Lenco/Pics/Lenco_4_10B.jpg

[Marra]

That's a nice finish.