Technics 1200 tonearm precision calibration

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flapjackthekandikid
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Technics 1200 tonearm precision calibration

Post by flapjackthekandikid » 19 Jan 2020 00:03

So I currently have been servicing a good 6 technics 1200s turntables I have here at my house, standard mods like new rcas, internal grounding (the jesse dean grounding pcbs are fantastic), pitch click removal (removing the board is such a hassle), pitch fader calibration, etc. etc. and all of the info for these is pretty readily available online. However, over literally the last 3 decades I've never seen anyone attempt a precision calibration repair for the 3 tonearm screws and bearings on the main arm pivot assembly. I've heard that they are machine-calibrated at the technics manufacturing house to be within a micron of each other for maximum tracking/efficiency, and while I do understand this, the price of replacement arm assembly (not even with the height adjustment) is pushing 200$ on the cheap end now as opposed to the 50 dollars it used to be in 2012. I was curious if anyone had any input on what tools would be needed for the hypothetical job, however expensive, and if anyone has the machined settings for actual recalibration of those pins ON the pivot. I KNOW buying a new joint is the main option, but wouldn't it be beneficial for the information to exist so people with the proper precision tooling could potentially repair unscrewed/loose units?

lenjack
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Re: Technics 1200 tonearm precision calibration

Post by lenjack » 19 Jan 2020 02:12

If you're talking about the pivot adjustment screws, I know Technics made available in the late 70s a special screwdriver, they gave away for nothing to adjust these. Mine is 40 years gone. Don't know where to get one. You might check at kabusa.com or organdonorparts.com.

flapjackthekandikid
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Re: Technics 1200 tonearm precision calibration

Post by flapjackthekandikid » 19 Jan 2020 02:35

the special screwdriver key is easy enough to get, it's the knowledge on the precision required to adjust them back to optimal settings that I'm after

audiopile
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Re: Technics 1200 tonearm precision calibration

Post by audiopile » 19 Jan 2020 05:35

We all got really spoiled by being able to buy factory new arms for not much more than headshells -which is obviously ridiculous . The reason I replaced so many arms was because often the arm on a well -used/abused 1200 had been "adjusted" until it worked really badly. I strongly suspect that a Technics arm that hasn't been B%^&gerd by a previous owner/abuser will last in even radio station studio use for many decades. But flapjack's got a goodpoint- we are now seeing scarcity pricing beginning to take over the market for OEM/NOS Techie arms -this will predictably continue to drive the price up as time goes on and $200 right now is a good price . And for pity sake - almost the very last "repair" to consider on a 1200/10 is adjusting the arm bearings - you may well turn a good arm into junk. If someone could come up with the instrumentation/jigs to re-certify arms - eventually they will be able to make some money reviving the Pulls most of us have a box or two of laying around.

scho2684
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Re: Technics 1200 tonearm precision calibration

Post by scho2684 » 19 Jan 2020 08:59

Well, I do think its possible to adjust those bearings...
And while it may not be as precise as the factory, you can better the bearing points by polishing them as they are quite rough out of the factory...

I do believe that re-adjusting without taking them apart is what's killing them because the moment there is play its because those bearing points start to have "bumps" in the relatively soft material...
If then the adjustment screw is tightened the whole bearing assembly including the little house in which the bearing balls are sitting will get deformed...

I have done a few and till now still with "success" meaning I haven't heard any complains back.
I have done a SL1400-MK2 arm as well and that is still playing very well on my own records...

This is the 1400MK2 before and after:
Bottom bearing point 02.jpg
(66.79000000000001 KiB) Downloaded 79 times
Bottom bearing point 04.jpg
(68.34 KiB) Downloaded 75 times
Bearing points should be "polished" using a lathe or something similar, using wetstone...


This is a 1200MK2 bearing assembly taken apart:
20190907_171742.jpg
(100.3 KiB) Downloaded 78 times
I have no access to the specific tools needed, but its doable with a LOT of patients with normal basic tools...

lenjack
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Re: Technics 1200 tonearm precision calibration

Post by lenjack » 19 Jan 2020 15:53

When I did have the special screwdriver tool, 40 years ago, I did not have the associated knowledge on how to make the required adjustments, and as a result, I never used it, nor did I ever attempt to adjust any of these bearings.

audiopile
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Re: Technics 1200 tonearm precision calibration

Post by audiopile » 19 Jan 2020 17:01

Schu- thank you for the pics -this will inspire me to go lookin for the box of "pulls" aka junk arms in my basement and finally take one apart. I'm down to my last two fresh OEM arms and won't be selling those - so sooner or later are going to HAVE to service a bearing assembly -even if it's just clean and reassemble ( gotta love cigie smoke (-: and in the end when dealing with polluted bearings and no OEM replacements - do the best reassembly I can. Will I be able to readjust to the precision these bearing assemblies once had - personally -I doubt it ?

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Re: Technics 1200 tonearm precision calibration

Post by flapjackthekandikid » 29 Jan 2020 03:11

scho2684 wrote:
19 Jan 2020 08:59
Well, I do think its possible to adjust those bearings...
And while it may not be as precise as the factory, you can better the bearing points by polishing them as they are quite rough out of the factory...

I do believe that re-adjusting without taking them apart is what's killing them because the moment there is play its because those bearing points start to have "bumps" in the relatively soft material...
If then the adjustment screw is tightened the whole bearing assembly including the little house in which the bearing balls are sitting will get deformed...

I have done a few and till now still with "success" meaning I haven't heard any complains back.
I have done a SL1400-MK2 arm as well and that is still playing very well on my own records...

This is the 1400MK2 before and after:

Bottom bearing point 02.jpg

Bottom bearing point 04.jpg

Bearing points should be "polished" using a lathe or something similar, using wetstone...


This is a 1200MK2 bearing assembly taken apart:

20190907_171742.jpg

I have no access to the specific tools needed, but its doable with a LOT of patients with normal basic tools...
scho2684, how do you carefully polish the bearings pin? Also, I am mostly looking for how much pressure to apply to the screw. Someone messed with this deck that I just got and I unfortunately did not notice that the arm bracket sat slightly lower than usually meaning someone 'adjusted' the top pin and re-tightened it, but I only notice it skipping backwards when I'm scratching on it. The arm isn't shaky, the needle is fine, I've taken apart and recalibrated every part of this turntable except the dreaded tonearm that everyone recommends against adjusting. I mainly wanted to know if there is a precision screwdriver that can gauge the exact force needed to 'factory reset' a top tonearm pin and if I could accurately achieve that

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