The Bastard

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shane
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The Bastard

Post by shane » Wed Apr 19, 2017 12:10 pm

Take a nicely brought up young turntable from rural south Devon. Introduce her to a disco king from Japan and leave them to have an illicit liaison in a shed and what do you get? A Bastard!

I've been intrigued by some of these DJ turntables with their high torque DD motors, so when Adam Smith on AoS offered a damaged but working Vestax 2000 free to anyone who wanted it, I was first in the queue. It's a horrible turntable. The plinth is a big hollow plastic moulding, the platter is a thin steel pressing and the arm, which is straight and stubby with no offset angle, is flimsy and floppy. The motor however is a different story. It's a big nicely made self-contained unit with prodigious torque and a half decent bearing that could probably be improved to something quite good. The intention is to build the motor into a solid plinth built up from layers of 6mm MDF, possibly interlayered with bitumin pads or maybe lead sheet. It's not finalised yet. I'd like to have been able to use slate, but this is a low cost project, and I don't currently have the tools or the facilities. The platter is a spare Heybrook TT2 platter and sub-platter assembly that I've had knocking about in the shed since the early 80s. To give you some idea of the torque available I've had to drill and tap the platter and sub-platter and bolt them together to prevent the sub from spinning inside the main platter on start-up!

There's a surprising amount of electronics and a hefty mains tx to accommodate, so I may go down the route of a remote PSU box. It has the usual two quartz-locked speed settings, but can also operate unlocked with the speed variable by a slider pot between about twenty and eighty RPM. It also has a reverse button. I have no idea why.

The motor:
Image

Image

The bearing is a ball approx 4mm in diameter set into a recess in the bottom of the shaft, resting on a nylon thrust pad supported by a bracket (apologies for the crap picture of the pad):

Image

Image

Image

You can also see the slotted disk and opto sensor for the motor speed sensor.

I'm hoping to replace the nylon thrust pad with a hardened steel shim, and I've inserted a washer between the bearing bracket and the bottom cover. Once the motor's fitted to the plinth, i'll fit a bolt underneath which will be tightened up against the cover to provide direct support under the bearing.

As you can see, the power transformer is pretty big and will nee to be housed remotely:

Image

I haven't decided wheth to build the power supply and processor boards into the base or put them in with the trafo. They're quite big too:

Image

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Probably they'll go onto the bottom of the plinth.

I've put together a lash-up of push buttons, leds and vero board to bring all the switches into one place. This will probably go under a bit of black Perspex eventually:

Image

This is starting from min speed, moving up to max,then reversing. Revere is achieved within half a rotation:


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shane
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Re: The Bastard

Post by shane » Wed Apr 19, 2017 12:38 pm

Of course, it's going to need an arm, so I'm reviving a project I started about ten years age using a titanium squash racket shaft blank that Dad brought home from work once. When you consider that he retired in 1981, you can see this is not a fast moving project.

The geometry is Rega, the head hell is a butchered ADC magnesium jobbie, the counterweight and the round brass pivot housing were pinched from a Horrible Helius/Heybrook Hybrid that deserved a dreadful fate and got one, and the pivot is nicked from a roller- ball pen. It sit in the hex socket of a stainless cap screw fitted to the top of a brass fitting which was once the end of a Habitat curtain wire.

Image

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It's taken a year to get this far so don't hold your breath,but I'll keep you updated as I go.

How Ant manages to knock out his fabulously finished Lencos in about a week defeats me...

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cressy
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Re: The Bastard

Post by cressy » Wed Apr 19, 2017 12:48 pm

That looks like a very nice little project Shane i looked a the vestax decks last year while looking for a project for the same reason as you, the honking great motor in them.

Ended up buying the jvc ql-y5f instead as it came up at the same time and I love the jvc's, this is the fourth one ive had.

I'll be following this with interest to see what you can get out of it

Cheers ant

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shane
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Re: The Bastard

Post by shane » Wed Apr 19, 2017 12:56 pm

Thanks,Ant. I think the turntable has a lot more potential than the arm, but it should be fun.
Not sure yet what I'll do with it when it's finished. I'll never get rid of my TT2, so I'll probably have to find a worthy cause!

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Re: The Bastard

Post by Ant » Sat Aug 19, 2017 11:29 pm

Shane is the motor spindle tapered or is ir straight sided?
Hey, wait, I got a new complaint
Forever in debt to your priceless advice

www.bte-designs.weebly.com

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shane
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Re: The Bastard

Post by shane » Sun Aug 20, 2017 11:58 pm

Sorry Ant, only just seen this. The spindle is straight sided and had a tapered brass collar to locate the original platter. I removed it to allow the TT2 sub-platter to fit.

Haven't touched it for a while as life keeps getting in the way, but I'm hoping to get back to it in the next month or so.

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Re: The Bastard

Post by Ant » Mon Aug 21, 2017 12:31 am

No worries Shane, i ask as I have my eye on one of these that has a buggered arm and I fancy trying turning a platter.
The usual tapered hole in a platter makes it a pain in the arse as the taper is not usually anything standard, the straight sides make it alot easier.

Plus in getting the itch to make something new again.....
Hey, wait, I got a new complaint
Forever in debt to your priceless advice

www.bte-designs.weebly.com

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shane
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Re: The Bastard

Post by shane » Mon Aug 21, 2017 6:56 am

Good thinking. Once the collar is removed, you're left with a flat "platter" about 25mm diameter with three holes tapped M3. Dead easy, although removing the collar required judicious use of an angle grinder.

If you take the bottom cover off the motor to inspect and reinforce the bearing, be careful not to bend the optical encoder disc in the process.

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jack
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Re: The Bastard

Post by jack » Mon Aug 21, 2017 7:03 am

The first (and only) turntable I made had a platter of phosphor bronze that I turned from a casting on a Myford ML7.

It was my 6th form DT project. I also made the oil-damped unipivot arm, that went with it - still have bits of that, 40 years later...

FWIW, turning a platter is very very tricky to get right. Firstly, the casting has to be very good indeed, with no gas pockets or impurities. The actual turning is no hard at all, but you only have one shot at getting the spindle right - I used silver steel which is tool steel rod ground to very high tolerances - typically 1/2000th inch, i.e. half a thou accuracy. Then it all has to be balanced.
The spindle sat in a phosphor bronze cup, at the bottom of which was a stainless steel ball bearing - the PB was lubricated with a drop of watch oil. Plinth was made of Iroko.

I didn't use a tapered fit - used an "interference" fit, which meant drilling the platter to an accuracy of better than 1/1000th inch (typically 1/2000th inch), then heating the platter slightly and using a hydraulic press to inset the spindle.

It took ages and it only worked as the workshop supervisor used to be a toolmaker and really understood the Myford lathes.

I can't find the plans for the arm, but ISTR it was published in one of the electronics or HIFi mags of the day (mid-70s).
Nick
Ars longa, vita brevis

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shane
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Re: The Bastard

Post by shane » Sat Nov 09, 2019 7:03 pm

Part of first post with pics restored:


The motor:
Image

Image

Image

The bearing is a ball approx 4mm in diameter set into a recess in the bottom of the shaft, resting on a nylon thrust pad supported by a bracket (apologies for the crap picture of the pad):

Image

Image

Image

You can also see the slotted disk and opto sensor for the motor speed sensor.

I'm hoping to replace the nylon thrust pad with a hardened steel shim, and I've inserted a washer between the bearing bracket and the bottom cover. Once the motor's fitted to the plinth, I’ll fit a bolt underneath which will be tightened up against the cover to provide direct support under the bearing.
Image


As you can see, the power transformer is pretty big and will need to be housed remotely:

Image

I haven't decided whether to build the power supply and processor boards into the base or put them in with the trafo. They're quite big too:

Image

Image

Probably they'll go onto the bottom of the plinth.

I've put together a lash-up of push buttons, LEDs and vero board to bring all the switches into one place. This will probably go under a bit of black Perspex eventually:

Image

This is starting from min speed, moving up to max,then reversing. Revere is achieved within half a rotation:


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