Magna Audio's custom-made counterweight balance and armboard service!

[Magna Audio]

Here's an ebony disc sub weight for Jazzbones. 40m x 8mm, 15mm hole.

Left un-oiled / unpolished as requrested.

[JazzBones]

Here's an ebony disc sub weight for Jazzbones. 40m x 8mm, 15mm hole.

Left un-oiled / unpolished as requrested.

Hi Steve, looks good mate. Have to go down to the main Post Office depot as I was not in when delivered, damn!
For those of a curious mind this ebony disc is to add a little mass to a special bronze counter weight from Linn given to me some time back, to use on my Ekos. The Linn CW weighs 166gm on its own and the ebony disc will be bonded to this enabling me to have the finished weight closer to the arm pillar pivotal point. I'm using a Koetsu Black and spinning it around is a highly modded Tech 1210. The ebony disc will match Steve's ebony arm board and the cosmetic changes I have made to the deck. Pics as soon as all the jobs are completed.

Thanks SteveO for your workmanship.

JB

[Magna Audio]

Here's a 180g counterweight for MikeMusic destined for a Jelco / SPU combo.

[Magna Audio]

Here's a turntable pulley replacement project.

This is for an Cranfield Rock turntable owned by Nonsmokingman.



Here's a pic of another deck showing the motor and pulley arrangement.



The original speed adjustment was in the form of angling the motor so the belt would ride on a smaller / larger diameter part of the drive pulley, changing the gearing suitably. However this never really seems to have worked since the current owner has had the deck (could be something to do with the air slowly going out of the deck suspension bellows - but as these have been jacked up that is a bit dubious).

The platter runs quite a bit too fast. So the easiest way to correct this is to have a pulley that is the right size to start with - like most belt drive turntables.

The drive pulley also has deep flanges so a wide belt rubs on them causing speed instabilities. A new pulley with a slight curve (barrel) to keep the belt in the right place is called for.

First task is to remove the existing pulley that was on very tight - interference fit. Aluminium on the steel shaft of the motor.
These motors are like hens teeth and not at all an easy rebuild so no undue force much be applied to the motor or the deck in doing this.

I made a puller out of some bar steel and bolts and an old threaded knob / collar I had in the parts chest. I drilled a 4mm hole down the centre of the thread so 3 different lengths of rod could be inserted as the pulley was 'pulled' off the motor shaft.

Here is a pic of the puller in place.



The central large thread pushes on the motor shaft whilst the bar clamped around the pulley base and the collar brings the pulling force to bear.

Here's the pulley off the motor.


Next up is the make a perfect fitting pulley of the right diameter for 33 & 1/3 rpm, but a pair of or three opposing grub screws to hold the pulley in place against rotational forces.

To be continued.

[Magna Audio]

An update on the Elite Cranfield phonogram "The Rock" as the label on the back states...

Pulley made.




Using a strobe and checking the speed after 30mins warm up and with the stylus in groove I had a few goes at shaving fractions off to get it spot on.

Another view




The slight barrelling of the pulley drive surface has worked well. The belt stays spot on in the pulley centre once the motor angle is adjusted.

The TT takes quite a while to speed stablise. The owner assures me this is normal. Once it has stabilised it is a very sweet sounding deck with Ortofon Cadenza blue cart. BTW, this is a 33 1/3 rpm only deck.
The owner has two of these decks the 2nd one will be done shortly

[Magna Audio]

I am now working on a 2nd Cranfield Rock. This one suffered a sub-chassis to plinth spring trauma. 40+yrs use and some of that time it being stored with a heavy weight (other equipment?) took its toll.
The springs lost some spring and receded. As they are set in many kgs of resin replacement is not easy.

The solution is to give them a boost. I made 3 raisers that fit between the sub-chassis and the plinth. This raises the coil spring tubes clear and all is nicely sprung again. Should give many more years suspension...



Here is one located on the coil spring


Here's a pic of the entire underside



The black paint is drying now so the risers don't show.

This one also needs a new pulley and a 45rpm one too. So that is next up.

[Magna Audio]

Just to let all you SL-1210 and 1200 fans know that I have obtained a test mounting deck to make armboard making easier / not requiring your deck in front of me to make armboards.

Decks that have not been converted to after market armboards do of course need modding. Rivnuts is the usual or I can make up steel blind nut inserts as I did for Marco's deck. These can be fitted easily (they just slot in) once the original arm is removed. They also have much tougher threads being of steel.

I do still of course need to know the arm base height relative to the platter, the spindle to pivot distance for the arm as well as the mounting hole or slot dimensions - best source for these is the arm manufacturers template. Of course having the arm to test mount is even better.

A wide range of Hardwoods can be used. Ebony and African blackwood best matching the SL-1210 of course.
For SL-1200's a silver lacquer spray finish can be applied.

Drop me a line to discuss as every installation is unique.

[Magna Audio]

Been busy on a new projects.

A Marble plinth. Cutting quite easy, drilling slow but possible. Top up the water to cool every 10secs of drilling.





BTW the other wobbly hole was cut by the customer not me!
There are two of these and they will go into something quite different... More on that later.

A little spacer to allow a fitting from a smaller dia arm to an existing armboard.


Armbase fitted


Ebony block for VPI deck board.

NEWS FLASH
I've bought myself an SL-1210 deck (again as I had one a few years back),to use as a template / mounting deck, so now I can make armboards etc / conversion kits with just the pivot to spindle distance known. No need for customer deck to be here.

So the armboard service can go mail order as well

[belloire]

hi Steve. without reading all 22 pages of this thread, what would i need to give you in order to have a bespoke arm board made? (if it's possible at all )

is it just measurements or the armboard as it stands now + new measurements etc? it's not exactly a common turntable/arm combo - Pioneer PLC-590 + Audio Technica AT-1005 mkII

[Magna Audio]

Hi,
I'd need measurements - easy if its just a block or round but some have intricate cutouts and indents.
Best of all would be to send me the original so I can clone it. The new pivot to spindle would need to be established from measuring on your deck and marking out, on for example masking tape, where the new arm hole is to be.

Regards,
Steve

hi Steve. without reading all 22 pages of this thread, what would i need to give you in order to have a bespoke arm board made? (if it's possible at all )

is it just measurements or the armboard as it stands now + new measurements etc? it's not exactly a common turntable/arm combo - Pioneer PLC-590 + Audio Technica AT-1005 mkII