Lightweight sl120

[Graeme]

Thougt i'd start a thread on this as its build will be slowly starting soon.
At first it will be an experimental build, then if all goes well ill build a nice looking version :)

Bit of background, i have gone from rega TT's many years ago to a lenco idler. Lenco got various plinths ending in 75k of slate!
I use a diy air bearing linear tracker.

I bought an sl120 cheap, and a sme3009. Ended up taking the motor out of the sl120 and fitting it into some very dense ply so i could fit my linear arm.
This, so far, is my favourite set up, but far from pretty.

I used to work for rega. I was turntable supervisor and the only builder of all the high end TT's. While working there i used to chat alot with Phil (head honcho below roy) and he used to keep me updated on the designing of the super deck there designing (cant remember the name, begins with N).
Anyhow, while im not a believer in low torque, their theory of light weight intreagues me so thought i'd try out this approach with the technics.
Im not sure it needs a high mass plinth as there is little vibration/noise to deal with in the first place, unlike my old idler.

So, the plan is to build a super lightweight, very stiff, minimal plinth. Ill do everything i can to minimise mass. Current thoughts are for a carbon fiber and aluminium honeycombe laminate.

I also planned to change out the platter and bearing. Not sure what for yet (should have got a P9 platter/bering while i was at rega), but something will be sourced. Main criteria is dimensional accuracy.

So, thats the current plan. Anyone gone down this path before?
First thing is to get the current lash up safe (lots of exposed mains voltage right now) have a good listen (hifi has been boxed up for 15 months due to house move), then ill reduce the current 'plinth' as much as possible to see if that heads in the right direction or not.
The theory is less mass so it doesnt act as a big 'resonance capacitor' and to push the resonant frequency up as high as possible. Tricky bit is retaining stiffness.

Updates will be few and far between at first, but discussing ideas before starting is never a bad thing :)

[Tarzan]

Graeme do keep us posted- and some nice piccies, sounds like an interesting idea

[spikeyfaz]

It's an old article but this might be of interest: - http://www.saturn-sound.com/history/the%20hi-fi%20section.htm#floating sub-chassis

The bit about the Technics is at the very bottom. :)

[Graeme]

Floating sub chassis, adding mass and a 12" pivoting arm:scratch:

Sounds horrid to me :)

Pretty much the exact opposite of my plan, although all the choices he made would have been to overcome the same percieved issues, he just went the other way.

[Graeme]

Ive been wanting to post latest pics but the phone to computer link is no longer working.

I finished the external PSU, re-capped it while it was out.
Ill get pics on eventually.

Im also having other thoughts about plinth design.
There is a second design ive been wanting to build for a while, but it wont be lightweight (or that heavy) but incorperates a built in air bearing linear arm. The benefits of this plinth design would be in a far simpler connection loop between bearing/plinth/arm/stylus with fewer material junctions.

Maybe ill just have to build them both :)


Oh, and i made a mistake in the title, the TT is a sl150. I binned the original plinth ages ago so had forgotten the model number.

[DSJR]

The original plinth and platter aren't bad at all, but the rubber feet need to be bypassed in my experience - just thought I'd mention it to anyone else contemplating an SL150 in series 1 form anyway. The transformer in these is under the top plate with extra screening, so NO hum issues AT ALL!!!!! The gentle servo shouldn't have the 'noise' attributed to the quartz version and shouldn't need the gumph that's done to the SL1200mk2 series either.

The 150 main bearing seems tight enough on the two samples I've had through my hands and a good dose of Rega's favourite EP80 gear oil seems to work well here, especially with the plastic (whatever material) thrust pad flooded with the stuff. The platter is VERY easily damped too, with the addition of any mat, so don't ditch immediately. As for mat, the original one on isn't bad, although I stuck a cork one on top to get the arm level (SL1500 tonearm with fixed-height bearing).

Only other thing to suggest as this is a definite age-related failing on these old Techies, is to make sure the mains switches and speed presets, both top plate ones AND the circuit board master presets, are cleaned with Servisol or even replaced, as wildy intermittant speed issues are all down to contaminated pots and switches.

Good luck with your project, and loads of piccies please :)

[Graeme]

Pics once i sort out the software, ill start a thread about that actually, see if anyone can help.

The sl150 is a great TT to play with as its very easy to trasnplant the electronics. Whats left in the plinth is very minimul, just the motor and 4 diodes, everything else is in the seperate PSU. Means you need a 12 core unbilicle though but i ended up using a D type 15 pin connector and some 25 core cable (doubled conductors).

Just solved an annoying speed instability. I've re-capped the PSU, disasembled the pots to clean thoroughly and cleaned the main trim pots on the board but it was still wavering slightly.
Im sure it didnt do this 2 years ago as i have previously had this TT on a calibrated wow/flutter meter where it gave fantastic results.

Anyhow, stupid me missed two other variable resistors on the board which obviously were set at manufacture. A little tweek and re-set on these and its now bang on stable again.

[Graeme]

I can do pics again :)

So, here is the quick lash up PSU for the sl150.

Its not very neat, and not very pretty, but ill build something decent when ive finished building my garage and have a bench to work at.

Outside, 45/off/33 and the speed controls
http://img.photobucket.com/albums/v242/GraemeVW/technics002_zpsb47d336a.jpg (http://smg.photobucket.com/user/GraemeVW/media/technics002_zpsb47d336a.jpg.html)

All the electronics now live in here. Has been re-capped since this pic.
http://img.photobucket.com/albums/v242/GraemeVW/technics001_zps3a06df32.jpg (http://smg.photobucket.com/user/GraemeVW/media/technics001_zps3a06df32.jpg.html)

Which means all that needs to be mounted in the plinth is the bearing/motor/board with 4 diodes.
http://img.photobucket.com/albums/v242/GraemeVW/technics003_zps8c550c39.jpg (http://smg.photobucket.com/user/GraemeVW/media/technics003_zps8c550c39.jpg.html)


This is why i like the sl150. Good performance, a 'proper' oil tight bearing, and easy to make whatever style plinth you like as you dont have a large pcb to house.

Still not decided what to do with the plinth, i think for now i might make a nice veneered plinth with an inegral air arm as i can make that in my kitchen, and once the garage is finished i can build a super stiff, ultra lightweight plinth and see if its any better.