ARMod II turntable project begins.

Wayner · « **on:** 28 Feb 2009, 02:00 pm »

Today I'm going to start on ARMod II. I gave Frank my good table and now all I have is parts so it's project time. The design is based around the VPI HW-19. I will have a solid wood plinth made of Alder that floats on 5 cushion points. The motor assembly will mount to the small triangle piece and will be located in the upper left had corner of the table. The motor assembly will be firmly attached to that and the walnut frame as I will glue the corner piece to the frame. The weird triangle piece is the sub-plinth and it will have the turntable bearing mounted to it, isolated by some elastomeric junk, making it slightly suspended, and it will be adjustable. The Motor is a Hurst 300 RPM Synchronous with an AR pulley. The plater is from an AR as well. The tonearm is a Rega R200. The Anti-skate device is broken on this tonearm, so I will have to put a dead man weight on it like I did on my Empire.

My main concern is that the motor will not be isolated enough. But I have lots of plasticlay on hand and all I have left to do is drill press work and then I can start assembly. The friend that made my cabinets for the Dynaco speakers also made the wood pieces for this table project. I hope I don't screw it up.

Wayner

rcag_ils · « **Reply #1 on:** 28 Feb 2009, 03:21 pm »

Regarding to your R200, how do you know the anti-skate is broken, is it because when the knob was turned you didn't feel any resistance from one end to the other? If the anti skate belt is indeed broken, the anti-skate mechanism needs to be reset back to zero before weight can be applied accurately, to do that involved a total disassemble of the tonearm base.

I successfully rewired one of these not too long ago, the wires are smaller than 33 awg. I considered it was my the biggest accomplishment in audio project. Fortunately, the anti-skate on mine is still working since I feel resistance from one end to the other, and it's audible when it's set incorrectly (imbalance in both channels), I set mine at .5 gram less than the tracking force applied, which is the ideal setting from listening test, and also correlates with other R200 owner's finding.

Wayner · « **Reply #2 on:** 28 Feb 2009, 05:29 pm »

If you take the knob off, there is a small "timing" style belt inside, that is broken. I origianlly bought this arm to use on ARMod I, but discovered the problem. It will not work properly without the anti-skate, so I will make one.

Wayner

rcag_ils · « **Reply #3 on:** 28 Feb 2009, 06:02 pm »

What if you need to subtract the anti-skating force from the original setting insteading of adding more, how could it be done with the belt broken?

Tone Depth · « **Reply #4 on:** 28 Feb 2009, 07:27 pm »

Hi Wayne,

There seems to be some interest in how you will apply a dead man weight for your anti-skate. My old Pioneer PL-12A had a bent bar mounted on the arm assembly, notched in about five locations to hold a piece of fine monofilament line to which a weight was suspended. The notched bar permitted repeatable adjustment of the amount of anti-skate applied. The monofilament line ran through another fixed wire-mounted hook mounted on the same platform as the arm. This enabled the weight to rise or fall as the arm moved through it's path across the LP. The fixed wire hook could be mounted on either side of the arm, depending on the need to add or subtract anti-skate. Is this similar to the idea you have in mind?

Wayner · « **Reply #5 on:** 28 Feb 2009, 08:24 pm »

I'll do this arm like I did the Empire:

Wayner

rcag_ils · « **Reply #6 on:** 28 Feb 2009, 09:42 pm »

Let say the anti-skate belt on the R200 broke when the anti-skate force was set at 1.75g, and now you need to set it at 1.25g or less, how would you accomplish that?

The R200 utilize a magnetic system for that anti-skate, I am not very clear how it work, but once the belt turn the base column for the anti-skate force, it's set until the belt turns the column to a different position.

R200 restorer usually disassemble the base, reset the column to 0g, then rig up some anti-skate weight system.

Also by looking at your Empire, the anti-skate already set at about 3g, with the weight there, it has to be above 3g, unless you disable the original anti-skate inside prior to hanging the weight. I am not familiar with what anti-skate system Empire utilized , or how your got broken, however.

Tone Depth · « **Reply #7 on:** 28 Feb 2009, 09:50 pm »

Excellent, it appears that you can change/modify the weight to dial in exactly what anti-skate you require. Simple, straight-forward. I like it.

Wayner · « **Reply #8 on:** 1 Mar 2009, 12:35 pm »

The anti-skate on the Empire is set to zero. That is with the small knurled knob above the tonearm where the thread is attached. The larger dial is for setting tracking weight, which I don't use either. That is also set to zero. I dial the weight in by just moving the counter-weight, using my Shure stylus force gauge.

I suspect that you may be right about the anti-skate being set to some "unknown" value. How ever, it still isn't enough. I will raid the fishing tackle box again and make my dead-man weight guess at the weight I need. Lucked out the first time with the Empire.

Wayner

Wayner · « **Reply #9 on:** 1 Mar 2009, 12:39 pm »

Here are some photos of a semi-put together table.

Should get it done today.

Art_Chicago · « **Reply #10 on:** 1 Mar 2009, 05:54 pm »

Hey, Wayner, this table looks great.
Are you making it just for fun? Seems like you have plenty of TTs.

Wayner · « **Reply #11 on:** 1 Mar 2009, 06:13 pm »

Art,

I had these parts laying around so I had to do something with them. I really enjoy building these tables. I suppose at some point I'll have to sell one or two of them. aa

Wayner

rcag_ils · « **Reply #12 on:** 1 Mar 2009, 08:41 pm »

If I had the opportunity to build a TT from the ground up (which I don't), I would mount the motor at the 7 O'clock position.

Most turntable's motors were mounted at the 11 or 12 O'clock position, when motor's energized, (since no bearing and suspension are perfect), the mechanical force's actually pulling the platter at an angle that's perpendicular to the cartridge, which affects the tracking.

Study has been done that when the motor is mounted at 7 O'clock, the force would pull the platter in parallel with the cartridge, which would affect tracking less..

Wayner · « **Reply #13 on:** 1 Mar 2009, 09:00 pm »

A motor at 7 O'clock may induce hum into a less then adequatley shielded cartridge. My VPI has the motor in the upper left hand corner too, and I just don't see it as a problem. However, my Empire has the motor at the 7:30 position.

Wayner

boycephoto · « **Reply #14 on:** 1 Mar 2009, 09:36 pm »

Wayner,

Nice looking table, what kind of motor is in the table, AC or DC? The only hum problems I have ever encountered is with with tables that have AC motors combined with a Grado Cartridge. My Linn has an AC motor (I think the Denon did also) and I have used several different Grado Cartridge's with it. They all would hum, and it got louder as the cartridge moved to the center of the turntable (closer to the motor that is mounted on the back left side). It was not loud and was not audible when I turned up the volume. The bigest problem was knowing it was there.

Good luck,
post a photo when you have it finished.

Cheers

Dave

Wayner · « **Reply #15 on:** 1 Mar 2009, 10:00 pm »

The motor is a Hurst direct replacement for the Hayden motor for ARs. I got the very last one from the Needle Doctor. I had to do a slight modification to the pulley (enlarge the hole) had a machine shop do that for me. I've used Hurst motors before and they don't bother the Audio Technica cartridge I'm going to put into it.

I have the motor running now. Thank God for platiclay. It sucked all the noise and vibrations right out of the assembly. I'll work on the tonearm tomorrow or Tuesday. I have to add some connectors to it and put a dead-man weight to fix the anti-skating. The Rega R200 seams like a nice tonearm. I hope it sounds good. Otherwise I'll have to get a Rega RB301 or something like that.

Wayner

oneinthepipe · « **Reply #16 on:** 1 Mar 2009, 10:30 pm »

Very impressive, Wayner. Very impressive.

TheChairGuy · « **Reply #17 on:** 1 Mar 2009, 11:40 pm »

Quote from: Wayner on 1 Mar 2009, 10:00 pm

Thank God for platiclay

...amen, brother

John

Listens2tubes · « **Reply #18 on:** 2 Mar 2009, 07:25 pm »

Wayne could you give a quick explanation of your external anti-skate setup? I'm sorry if you have done this before in another thread.

turkey · « **Reply #19 on:** 3 Mar 2009, 04:45 pm »

Quote from: oneinthepipe on 1 Mar 2009, 10:30 pm

Very impressive, Wayner. Very impressive.

I agree. Very cool project, Wayner.