Gray Research / Microtrak 306 Pedestal - Presto 8D

[EpicenterBryan]

Hey guys, thought I would show you another project I've been working on.

I really wanted a 16" tone arm to use on my 8D since I can cut 16" discs but had no way to play them back. Obviously there are some advantages in using 16" discs when I'm messing around since there is so much cut time per side to experiment with. And since I got a good deal on a box of 25 of them, the cost per minute was very attractive. Also, being able to play the groove being cut would be really handy in setting reference level on the disc, and also for setting up a heated stylus at some point.

Some might remember my "tower of power" servo mod from this link:
http://www.lathetrolls.com/viewtopic.php?f=15&t=6212

I set that "tower" project aside until I had time to investigate some other belt material. The last 2 weeks, I decided to temperately re-purpose the tower for use as a tonearm pedestal.

Here it is in it's full glory!

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As you see, it's a self contained unit with RCA jacks in the back and it's own tonearm rest stop.

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You might notice that the logo on the tone arm changed midway through the project (from Gray Research to Microtrak). That is a little twist that really messed me up ...

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[EpicenterBryan]

There were 2 tonearms involved. Both were obtained on E-bay over the last year.
First off, the Gray Research:
This was the first one and should have been a no brainier. I stepped up to the plate on this one because it was so complete and looked to be in great shape. The only down side was there were 2 wires in the head shell that were cut short and needed to be extended and have cartridge sockets installed. No big deal.

So I repaired the head shell built things up and had a dead left channel. Eventually, I traced it down to the black and green wires being shorted inside the tonearm somewhere between where the shielded wires enter the tonearm (and are potted), and the connector at the end of the tone arm. So I decided to try to abandon one of the two wires and run a new one through the shield up to the tone arm (the blue wire). Then I ran the wire on the outside on the bottom of the tone arm up to the head shell. (no photo taken).

Here I'm pulling those wires back through the shield including the extra blue wire...

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Two problems here:
First, there was hum pickup. So I thought I would either cover the external wire with copper tape and then connect to the shield, or perhaps order some shielded wire - and that brings up the next issue...
The second issue was that the only really small wire I had was not stranded, just solid core 30awg wire-wrap wire. That turned out to be slightly too stiff and made the tonearm skip when tracking at 1.25g.

The second tonearm was a Microtrak. It had good wires but the area at the end where the head shell mates was split and so it wouldn't hold a shell... and the connector at the end was messed up.

In the end I was able to pull the wire harness out of the second tonearm (it had RTV, not hard potting), remove the connector in both the tonearm and the head shell, and reshape and build up the broken areas at the end of the tone arm. Then I glued the head shell on the tone arm. I then wired it up without either of the connectors and it worked fine.

But, that raises the issue of the Gray Research tonearm. The wires are potted as well as the connector. I can get them out by destroying them. So now I need a resource for shielded (non jacketed) 4 conductor really fine twisted multi strand tone arm wire.

Thoughts?

Bryan

[Soulbear]

Hi Bryan,
Have you looked at Sommer Scuba Miniature Mic and Line Cable? Sure its got a Sheath/Jacket but this strips off very readily (I Know because I've used it!) so you can minimise the Overall Cross Sectional Area :- https://www.studiospares.com/Cables-Leads/Cable-Miniature/Sommer-Scuba-Miniature-Mic--Line-Cable-Black_540401.htm


SOMMER CABLE - SC-SCUBA 14 HIGHFLEX The SC-SCUBA 14 HIGHFLEX will go right along with you. It is very thin, saves space, is flexible, excellently suited for connectors with a small diameter, for example LEMO patchboards, mini-jacks, cinch, etc. and rack cabling. The diameter and wire construction has been configured according to common broadcasting norms and dense copper braiding with 90 % shielding protects the cable from interference.. THE ADVANTAGES: * Very thin, high tensile strength and flexibility * Available in five different colors * Good shielding due to dense copper braided shielding * Very reasonable price APPLICATIONS: * Patch cabling (LEMO), gooseneck microphones * Home recording * Rack and console cabling. Jacket diameter 3.8mm
Maybe something along these lines???
Regards Soulbear

[sameal]

I was thinking about putting mine where the dish is on the left hand side of the "anvil".

But i haven't done the math yet if itd work without getting in the way of the scope.

I might take your route.

[EpicenterBryan]

But i haven't done the math yet if itd work without getting in the way of the scope.

If you are also using a 306 (16" tonearm), all you have to do is make sure the center of the base is 10 5/8" from the center of the spindle on the lathe. Putting it in the front means it's a bit clunky if you are right handed. But I found a guy in the Ukraine who makes a lifting device like shown below that fits the 303 or 306 tonearms. He lists them on E-bay from time to time but they are not on there right now.

He said he can make them for other tone arms as well. I'm not sure if this is oil damped but it's way better than nothing.

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Bryan

[EpicenterBryan]

UPDATE: I just got an E-mail from Serge Karmadon who makes the lifter, and he says the lifter is in fact damped with 600,000 cst fluid which is the same used in the Micro-Trak as anti-skate fluid.

Bryan

[EpicenterBryan]

Serge looked at my photos and mentioned he can also make the lift mechanism for a 303 or 306 tonearm with an integrated tone arm support. So this is the one I've gone for. I'll delete the tonearm support I currently have.

Check this out. How cool is this? It's about $20 USD more than the other version.

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Should be here in a few weeks...

Bryan

[sameal]

Very cool!

I might have to purchase that as well!

Im going to be using a rek-o-cut 160, just as soon as i figure out why the weight adjustment only puts the tonearm in the air.

[Gridlock]

Dude playback is so important.... This setup rules and clears the platter by....how much bryan? I would guess 1/16"? I almost had a panic attack on seeing the tiny clearance. Its like watching someone jump a moped over a bunch of pregnant women...

[EpicenterBryan]

....how much bryan? I would guess 1/16"? I almost had a panic attack on seeing the tiny clearance.

Not to panic - it's closer to 1/8"
Yes, the clearance is very small but doesn't need to be that way. Remember, I was temperately re-purposing the servo tower for now. I'll be building a new tonearm tower that has a smaller footprint eventually. This works for now.

I got the tone arm lifter with integrated tonearm support! I've got to share my experience and a few photos:

This came from Serge Karmadon in the Ukraine. His website is http://www.karmadon.net . He specializes in restoration and repair of turntables, tone arms and such. Check out his site for more details...

But I also wanted to share my experience in dealing with Serge. As you know I dropped him a line about his lift mechanism for the Gray Research / Microtrak 303/306 tonearm and asked a few questions including if the lift was damped. He responded immediately. I also asked if it had been checked with the 306 (16 inch tonearm) to make sure the wires cleared and sent him a photo of my setup.

This is where it gets really cool: He replied that the wires would clear and also sent a photo of another version I didn't see on his site that had an integrated tonearm support. That version would let me eliminate the tonearm rest and extension from my earlier setup. We exchanged another e-mail about the price difference and I settled on the integrated version. He set payment instructions, and after sending payment I received the tracking number the next day.

To my amazement I could actually track the package from the Ukraine all the way to the USA, and it showed up in just over a week!

Anyway, I for one had a very good experience with Serge and karmadon.net. I'm always thrilled when someone takes the time and extra effort to look at what you are doing and suggest an even better solution you may not know about. That's great customer service in my book.

I also want to mention that the version I bought needed a tonearm rest that was rectangular, but he also has round ones for normal tube style tone arms. And he can bore the clamp to fit other tone arms as well... So if you have a different tonearm and are interested in either lift mechanisms I have shown, you might want to drop him a line. My gut says he can tweak the design to fit your application if he hasn't already.

So that's my put as a happy customer. Your mileage as always may vary.

So here are the updated photos!
Look Mom, no hands (or external tonearm support)!

Bryan

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