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Author Topic: "Spring scale" in an Otari MX70?  (Read 2689 times)

ricknroll

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"Spring scale" in an Otari MX70?
« on: January 03, 2006, 08:51:42 PM »

I'm going through the manual for my Otari MX70 and trying to set it up properly.  I've verified the phase of the tach pulses is correct, adjusted the position of the tension arm sensors, and the next step involves adjusting the force of the tension swing arms.  Step 3 on page 4-11 of the manual reads, "Attach the spring scale (0 - 4000 Grams) to the string."  My question is:  What is the spring scale?  I don't see a reference to this in any of the pictures or figures in the manual.  The tension arms are connected to a spring contraption, but a few steps later the manual instructs the user to adjust a trim pot on a PCB to achieve a specific tension (2 kg).  There are no markings on the spring device, so it seems like there must be some tool they're referring to.  The beginning of the setup section in the manual lists the needed equipment (oscilloscope, DC volt meter, frequency counter, oscillator capable of producing square waves, and specific hex wrench sizes) but there's nothing about a spring scale mentioned.  Is there actually some kind of standard spring scale thing that I need to get that is simply not mentioned in the manual?

Thanks,

Rick
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Larrchild

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Re: "Spring scale" in an Otari MX70?
« Reply #1 on: January 03, 2006, 09:38:45 PM »

Yes. It looks like a fish scale from a tackle box. Tension pulls on a spring and makes a pointer move depending on pull. If you are desperate and you can convert Kg to Lbs, you can use a fish scale or something similar.

If you get all this dialed in and set it by the book, one last test to check relative tensions is to hold back the pinch roller from engaging for a few secs and hitting play and see if the tape runs forward and near play speed with half of the tape on each reel. This means you are close.
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Larry Janus
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Brian Roth

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Re: "Spring scale" in an Otari MX70?
« Reply #2 on: January 04, 2006, 02:01:48 AM »

I have several ancient metal Chatillon scales I got for adjusting Ampex machines.  In later years, I needed additional ranges, so I filled in the gaps with some of these:

http://www.scientificsonline.com/product.asp_Q_pn_E_3001000

Bri



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bobkatz

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Re: "Spring scale" in an Otari MX70?
« Reply #3 on: January 04, 2006, 05:07:20 AM »

[quote title=ricknroll wrote on Tue, 03 January 2006 20:51 "Attach the spring scale (0 - 4000 Grams) to the string."  My question is:  What is the spring scale?



Rick[/quote]


That's Japlish for "Attach a spring scale". You do have to get one of those. Although I've cheated and estimated more times than you can count I still have my spring scale in some drawer. If it's a pressure roller, one trick is increase the pressure until the solenoid no longer clunks and doesn't bottom, then reduce it by one turn. Not very scientific, but it worked on Otaris and Revoxes...

But if it's reel tensions, it's best to use a Tentelometer, it's more exact. Tentel gave recommended values for different sizes of tape and it worked fine.


BK
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ricknroll

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Re: "Spring scale" in an Otari MX70?
« Reply #4 on: January 04, 2006, 11:11:35 AM »

Once again, the John Klett forum saves me - thanks guys!  I looked at the Tentel web site and those Tentelometers are pretty damn pricey, at least given what will be my limited use for the scale.  I saw one on eBay but I'm not sure it was exactly what I need, so I think I'm going to go with one of the scales in the link provided by Brian.  As always, thanks for all the responses..hopefully some day I will be able to return the favor.

Thanks,

Rick
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