Post by Graham on Dec 19, 2019 9:34:53 GMT 12
I thought I had better start this thread with a before shot showing the 'kitset' collection of parts in their original state. The all important main spindle bearing is still in fine condition. The motor and motor control circuit all work correctly with the 2 speeds able to be selected and with the fine adjustment functioning. I will strip everything down for a thorough clean and inspection and then assess what is required for the restoration. Watch this space.
 
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Pundit
Post by paulsaints on Dec 19, 2019 16:24:11 GMT 12
"The motor and motor control circuit all work correctly with the 2 speeds able to be selected and with the fine adjustment functioning." - That's brilliant! especially on top of a good bearing.
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Post by Citroen on Dec 19, 2019 16:31:33 GMT 12
Yes indeed. The major potential problem areas looking good. Have you tested the actual speeds Graham? A domestic rubberband can work for flat belt between motor and flywheel if you need to test. So only a bit of cosmetic work and you've got yourself a very nice quality table, Paul
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Post by Graham on Dec 19, 2019 19:53:42 GMT 12
Yes I have tested the actual speeds on the platter with a jury rigged belt and my strobe disc.
Both speeds can be selected with the toggle switch and adjusted plus or minus with the trim pots.
Once adjusted the speed is rock steady on both 33 and 45. Well it was until my glued together temporary belt broke !!!
The loose wobbly support column is now sorted. I managed to undo the seized capscrew underneath, cleaned the old Loctite off the threads and reassembled and tightened.
Looking good.
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Post by Graham on Dec 19, 2019 20:23:25 GMT 12
Although the restoration is not planned to begin until after Christmas I couldn't resist giving the tarnished brass pulleys a bit of a polish. 
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Post by Owen Y on Dec 20, 2019 10:50:03 GMT 12
A test for the motor system later, will be how well it starts the heavy platter + flyweights. ( Graham - let me know what is the diam. of the motor pulley (5-6mm?), the flywheel lower & upper diam. (60-70mm?) - I'll calc the gearing & motor speed.) (The gearing was Dave's way of enabling a low torque motor to reasonably quickly start up the 15kg platter-flyweights.)
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Post by Graham on Dec 20, 2019 12:34:46 GMT 12
Motor pulley diam = 4.5mm Flywheel Lower diam = 74.3mm Flywheel Upper diam = 71.3mm Platter diam = 300mm
The supplied wallart PSU has output stated as 12 volts ac 830ma, not 16 volts, but seems to work fine and will start the heavy platter and bring it up to speed in a few seconds.
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Post by jon on Dec 20, 2019 15:04:38 GMT 12
Although the restoration is not planned to begin until after Christmas I couldn't resist giving the tarnished brass pulleys a bit of a polish.
Hehe, methinks Graham is quite excited by this rebuild...
Scheduled for after XMAS 
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Post by jon on Dec 20, 2019 15:05:17 GMT 12
Don't get me wrong, I would be too!
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Post by Owen Y on Dec 20, 2019 16:21:49 GMT 12
Ah OK, you have already rigged up belts to platter & tested. Gearing overall looks to be ~71.0, which means that the mtr is running at ~2370rpm at 33.33 platter speed. And ~3200rpm at 45rpm. (Max mtr spd was 2700rpm IIRC.)
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Post by Graham on Dec 23, 2019 9:41:46 GMT 12
I'm after some advice or input from the combined brainpower and experience of this forum. ( Hows that for a challenge )
I greatly admire the sound engineering and continued development of Dave's Auro turntable over the years of it's production, but have to confess I find the suspension system comprising a loose collection of coil springs, squash balls and sorbothane pads a bit 'Heath Robinson'.  As this particular Aura has no suspension components provided other than one lonely spring I think this gives us the opportunity to rethink this area and come up with something more in keeping with the otherwise excellent design and maybe using more recent technology. The only critical feature or restriction is that the two steel plates that form the base must end up approximately 20 -25 mm apart when the turntable is assembled and resting on the suspension. The weight of this sprung mass is 25kg. So in between drinking far too much and stuffing ourselves with lovely food have a little think about what configuration this could be. All suggestions will be gratefully received. Merry Christmas. 
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Pundit
Post by paulsaints on Dec 23, 2019 14:01:02 GMT 12
and would anyone with a genuine Aura record-clamp be kind enough to weight theirs - don't want to de-stabilise things with a grossly over-weight record-clamp.
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Post by Citroen on Dec 23, 2019 16:26:36 GMT 12
I've ditched the sorbothane pucks and springs and replaced them with Polycrystal isocones.
1. They provided a rigid, more stable platform
2. They were low enough in profile to work
3. They lowered the noise floor, tightened the bass, and made everything more "real".
The only downside was a slight loss of "air"/"lightness". YMMV.
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Post by Citroen on Dec 23, 2019 16:35:00 GMT 12
and would anyone with a genuine Aura record-clamp be kind enough to weight theirs - don't want to de-stabilise things with a grossly over-weight record-clamp. A genuine Aura clamp? Mine is just a lightweight piece of persplex, that weighs next to nothing. Additional weight of a record clamp would be negligible to the operation of the turntable IMHO, as it would be a fraction of the mass of the actual turntable platter. What weight clamp are you thinking of using?
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Pundit
Post by paulsaints on Dec 23, 2019 17:19:33 GMT 12
The original was not with the parts that came with this restoration, but it looks quite lightweight with three points that seem to touch the record. So it's not that I am targeting a specific weight, more that I would like to look for something close to what was original, so I am interested to know what the original weighs. Pics attached.  
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Post by Citroen on Dec 23, 2019 17:33:06 GMT 12
In terms of record clamps the original does next to nothing.
Its a lightweight piece of persplex that only pushes the inner surface of the record to the platter. The outside edges are either unaffected or made worse by being dished outwards.
There are many more worthwhile clamps or weights to use, IMHO.
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Post by Owen Y on Dec 23, 2019 18:59:33 GMT 12
This is the Aura clamp - 88mm diam x 6.3mm acrylic: (Rubber o-rings around the knob, have perished.)  
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Pundit
Post by paulsaints on Dec 23, 2019 19:28:14 GMT 12
so it doesn't work by weight but by "grip". Thanks for that.
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Post by Citroen on Dec 23, 2019 21:59:18 GMT 12
My clamp didn't come with those silicon feet, and is slightly thinner at 5.5mm thick  In any case I prefer my basic Clearaudio Twister clamp 
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Pundit
Post by paulsaints on Dec 24, 2019 6:21:22 GMT 12
I think that the "learning" for me for the Aura is that it needs a lightweight "grip-style" clamp, which makes sense if the engineering design of the Aura is for a "lightweight" platter with weights added at the periphery to give tangential force? then the last thing you would want is a heavy record clamp adding mass at the centre (compared to my lenco with its heavy platter and motor on which I happily use a 400g record clamp).
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Post by Citroen on Dec 24, 2019 8:15:58 GMT 12
Don't be so quick to come to that conclusion. Some Aura owners prefer a heavy weight, rather than clamp. Might depend on what mat you're using, or personal preference.
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Post by Owen Y on Dec 24, 2019 8:37:08 GMT 12
As mentioned previously, I never use a record clamp & have never used one on the Aura. Regardless of platter or TT design, IMHO clamping robs the sound of dynamic range, harmonic decay & low-level information. Of course, YMMV.
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Pundit
Post by paulsaints on Dec 24, 2019 9:17:36 GMT 12
I can see that people will choose their own preferred clamping or non-clamping, but at this point I'm just trying to honour and understand the engineering behind Dave Whittaker's choices. The "light-ish" platter and heavy edge weights was a very specific engineering decision.
But back to Graham's question about the suspension between the two steel plates that form the base. I was wondering whether the use of both springs and sorbothane (rather than just one or the other) mirrored the springs and shock absorber combination on cars. Just springs on a car (even tethered) or just shocks on a car wouldn't work. Was the spring and sorbothane combo doing something similar for the Aura suspension?
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Post by Graham on Dec 24, 2019 9:49:52 GMT 12
Hi Paul
Yes I think that was the original intention. The collection of springs supported the weight of the turntable while the sorbothane acted as dampers.
Springs on their own would have been unstable with all that weight high above them. Sorbothane is far too soft to support the 25kg weight on their own. So a combination of the two was configured by Dave.
We could very well end up with that set up, but I am open to alternative designs that achieve a stable platform with a degree of vibration isolation.
One such idea rattling around in my head would be four pucks or donut shaped pads of fairly hard rubber ( natural or synthetic ) or even closed cell foam rubber.
Or maybe make it almost a solid base as Citroen has done with his. If for instance your mounting location for the turntable (when it eventually reaches your home) is solid and stable why have any suspension at all.
Lots of options.
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Post by Owen Y on Dec 24, 2019 11:44:21 GMT 12
Depends on the durometer density selected, but 4 x big Sorbothane hemispheres or such will support 25kgs no problem. However they will compress a bit, but together with springs, will handle things no sweat. I like Citroen's rigid approach too, experimental, although departing from "authentic". My Aura has springs & 4 x ~75 diam sorbothane 'pucks'. Using multiple devices like Dave did, he was able to support the unbalanced mass of the solid steel arm pillar/s at the back (or even a 3rd arm pillar at the front R - by distributing say more springs under the heavier corner and/or side. PS. paulsaints & Graham - is your platter not filled with solid material on the underside? (The original design was not, I believe.)
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Post by Graham on Dec 24, 2019 12:11:11 GMT 12
Still just kicking ideas around for various options but we will more than likely stick with Dave's original design.
Sorbothane pucks are readily available on the internet but not sure at this stage where to source the springs from.
The underside of the platter is filled with a plaster type substance.
At some stage in the new year I must visit Owen or Cliff to check what a fully assembled functioning Aura looks like.
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Post by Citroen on Dec 24, 2019 14:04:26 GMT 12
At some stage I need to give mine a spit and polish, as it's starting to look rather shabby and rusty (along with a lot of dust and dog hair).
Let me know if you can source some 1mm round belts. I need two as I'm currently making do with a single 2.5 mm belt.
I try to always use a clamp on the Aura but don't use one on any of my other turntables, apart from a Project one.
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Post by Citroen on Dec 24, 2019 14:05:29 GMT 12
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Post by andrewp on Dec 24, 2019 15:14:43 GMT 12
Man alive Owen....is there anything about these Auras you DONT know..!!!
You need to get yourself on the pay roll!!
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Post by Owen Y on Dec 24, 2019 17:07:53 GMT 12
Actually andrewp, quite a lot as it turned out. I spent a bit of time with D Whittaker in the early 2000s, but realised that I did not know quite a lot, when Aura owners (mostly overseas) all started getting in touch after Dave died in 2006. Drive belts (flywheel-to-platter) - count me in too, for a couple. You may have to get an o-ring kit & make up your own, around 1.1m circumf.
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