Logic DM101 Turntable set up problems - diyAudio
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Old 15th March 2013, 04:40 AM   #1
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Default Logic DM101 Turntable set up problems

Seems I'm a likely candidate to foist cantankerous equipment on.

Case in point: an 80s vintage Logic DM101 Turntable that the previous owner gave up on, saying it was a veritable "B*#*" to set-up.

I'm taking a whack at it and finding the process...indeed...daunting.

Balancing the floating sub-chassis on the three-point suspension system (comprised of six-expansion springs moored to the plinth) upon which the sub-chassis set screws attach themselves to (see pics) is proving near impossible.

The sub-chassis simply won't level out or center in the cut-away section of the plinth no matter how I adjust the leveling set-screws.

I have visited vinylengine and read through the set-up manual with no luck....so I am contemplating replacing the six suspension springs which don't seem uniform in terms of expansion-tension.

The second wonky (IMO) quirk of this system seems to be the centered main compression spring....

Does anyone have any experience with setting these up...any helpful hints? insights?

Thks...Leon
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Old 15th March 2013, 05:02 AM   #2
VaNarn is offline VaNarn  Australia
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The design of this turntable suspension was to ease the set up problem by having the three adjustable screws at the top.Apart from that, the arm connecting lead had to be coiled in such a way as to prevent any offset to the sub assembly.Given the age factor I would firstly make sure the connecting lead has not stiffened and secondly check that none of the springs have stretched.Sometimes it helps to add a piece of foam plastic or rubber inside the springs to provide light damping.
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Old 15th March 2013, 05:24 AM   #3
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Thanks...but everything I've read about these seems to indicate they have always been problematic in terms of balancing and set-up...the Thorens, Ariston and Linn are a breeze compared to this wacky beast.

No amount of set screw adjustment seems to alleviate the leveling of the sub-chassis and checking the arm connecting lead and phono-wires reveals it hasn't hardened or shifted from its original position.

I am going to try six new springs and see if that improves the leveling, keeps it as is, or makes matters worse.

I will also disconnect the arm connecting lead as well and see what that does, if anything...thks for your observations VaNarn!
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Old 26th March 2013, 10:45 AM   #4
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Did you get this sorted? There is a nack to setting this up but its fairly easy, vinylengine has the instructions or I can guide you through it if you like.
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Old 27th March 2013, 12:03 AM   #5
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Quote:
Originally Posted by robgilmo View Post
Did you get this sorted? There is a nack to setting this up but its fairly easy, vinylengine has the instructions or I can guide you through it if you like.
Thanks...yes..but the instructions are IMO horrible....and pretty much bereft of decent diagrams to illuminate the process...and after all the set-up, adjustments, a decent tonearm and decent MC cartridge...the Logic was not in any way superior to my ancient Ariston running a midddle of the road Nagaoka cartridge on a pertty ordinary Rega arm.
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Old 27th March 2013, 12:27 AM   #6
Toaster is offline Toaster  United Kingdom
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I did set one of these up 'back in the day' when it was only a couple of years old and would generally agree with the previous owners assessment! However, it was easy enough to get the chassis centered, so I imagine one or more of the springs has stretched. Always a bit twitchy even when nearly new. I'd put a hole through three 'soft shoe' style sorbothane feet and use those in place of the springs with the spring bolts used as guides. Did this with an early Systemdek relatively recently to good effect. This may require some simple fabrication to give the sorbothane something to sit on.
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Old 27th March 2013, 09:32 PM   #7
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You Brits are entitled to you opinion, of course, but the mainspring upon which the weight of the sub-platter plinth assembly really rests, is horribly conceived and implemented! It is little more than a large bedspring...poorly manufactured, machined and engineered. At the price these were introduced for...I've heard and seen many better under that price point....I got it sorted out just fine but as I said before...the Dm101 makes a Linn, Thorens or any number of other finicky decks at this price-point seem easy to set-up...probably why it never achieved any commercial longevity or success...regards..Leon
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Old 27th March 2013, 10:11 PM   #8
Toaster is offline Toaster  United Kingdom
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Totally agree- no doubt conceived at the time with the best of intentions, but a silly idea nonetheless. With or without the centre spring, which was not on the deck from the start but added as a later 'fix', the configuration of the springs does nothing useful. Like I say, best removed altogether.
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Old 29th March 2013, 12:00 AM   #9
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I found it very easy to set up and once there it stays there. One thing I did find is the cable for the arm passing through the centre spring, if you dont get this right all the adjusting in the world wont help at all, I often wondered if re-routing the cable might have made things easier. Also the orientation of the centre spring is important (according to Logic) as if done wrong can throw things off a little.
I use mine with a Logic Datum 2 arm and I think its a good table, better than my old Thorens/SME table which was a pain to set up, why turntable manufacturers think setting up a suspended table from underneath is OK is beyond me. I felt like a complete eejit lying on the floor underneath a record player balanced on two chairs trying to get the 'bounce' right , I'm glad none of my friends saw me.

Edit - your springs dont look worn to me, I did read somewhere that the outer springs were softened to accommodate the centre spring, the way your adjusters are sitting high one might assume yours was before this modification but after the centre spring modification. If you do modify it and no longer need the springs I would be interested in taking them off your hands if your random spare spring box is full.

Last edited by robgilmo; 29th March 2013 at 12:04 AM.
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Old 7th April 2013, 05:48 AM   #10
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Yes...rerouting the cable made things a lot easier to set up. It's not a bad TT, but the engineering of the suspension system particularly the center mainspring is ridiculously inept IMO...I like keeping things as simple as possible...and in this respect I simply don't hear an appreciably better result from finicky turntables like this and the Linns, Thorens etc. over meat and potato TTs like my Empire 298 or my Lenco L78.

And in the end that's what I am looking for...some quantum improvement over what I already have....particularly if the original price point between the items was as significant as in this case.

In any event I quickly disposed of this TT by trading it to a fellow enamoured by such complexity...I would note that upon moving the Logic to his domicile...we were forced to set the screwy beast up again almost from scratch.

We kept it stock...so sorry robgilmo, no spare springs kicking around...but thanks for your input, observations and advice...much appreciated...yours too...Toaster and VaNarn
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