How to fix my Cen-Tech 6" Digital Caliper

Discussion in 'General Electronics Chat' started by Gdrumm, Mar 9, 2015.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    I thought the battery was dead, but it is not.
    I removed a small tab at the top, and found these 4 traces.
    The two outer ones show 1.4 volts (as though coming straight from the battery).
    The small plastic tab (shown) has what may be some electrically conductive paint.
    I re-inserted it, and it worked properly for a few seconds.

    Does anyone have any experience with this (Harbor Freight Item 98563).

    How can I fix it?

    Thanks,

    Gary DSC00001.JPG DSC00002.JPG DSC00001.JPG DSC00002.JPG
     
  2. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    I think I got it working.
    There were 4 tiny screws on the back, under the label.
    I removed them, and soon found I couldn't disassemble it further with risking damage.
    So I replaced the 4 screws (one of them is a machined screw thread), and tightened them securely.
    Two other small set screws across the top bar apparently control the friction roller. I snugged those up a bit as well.
    Anyway, I've turned it off and on several times now, and it's working fine.
    It seems to be precise as well.
    Thanks for looking.
    Gary DSC00003.JPG DSC00004.JPG DSC00005.JPG
     
  3. BReeves

    Member

    Nov 24, 2012
    412
    64
    I was going to say throw it in the trash and buy a new one, they are really inexpensive (cheap). Glad you got it working.
     
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  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    905
    I had just run to get my copy of the caliper. On mine, the cover you removed just covers four contacts. There is no little metallic gizmo on it like you show. The 4 contacts are for reading it externally, like you see with Mitutoyo and other brands. The Mitutoyo and HF protocals are different.

    Glad you got it fixed.

    John
     
  5. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
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    My guess is that the screws (or at least one of them) had come loose over time, and that caused it to fail to make good contact.
    That being said, it might be advisable to tighten the screws every year or so.

    I recall throwing away more than one battery, sometime last year when a similar thing occurred.
    I thought they were dead (and they are not cheap... in Battery speak...

    Glad I checked the battery with a meter this time.

    It's always good to salvage a tool whenever you can.

    Thanks,
    Gary
     
  6. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    2,800
    1,237
    Inasmuch as the operation of such instruments is based upon electrostatic (i.e. capacitive) coupling to the 'rack' they are highly sensitive to moisture and other (polar) contaminants -- Should you experience further difficulty try wiping the rack with a cloth moistened (but not wetted) with an evaporating chemical dryer (e.g. 'neat' isopropanol)

    Best regards
    HP
     
    Last edited: Mar 9, 2015
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    These calipers just turn off the display when you hit the 'off' button, and as a result run the battery dead in a month or so. Remove the battery if you aren't going to use it again that day. The LR44 batteries are pricey if you buy them at a hardware store or even at Wally World, usually a couple of dollars each. I buy them in bulk, as our kitties' red dotmakers (toy lasers) use the same batteries. I bought a couple hundred of them for around $10 USD, delivered. They are old batteries that still have a full charge, but some of them tend to leak, so I don't leave them in anything important/expensive.
     
  8. MrChips

    Moderator

    Oct 2, 2009
    12,447
    3,362
    As Sarge says, I remove the battery after using.
     
  9. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    Two very good tips.

    I took the battery out just now.

    For frequent users that would be a pain, but luckily for me I don't use this caliper that often.

    I really prefer the old "Dial Caliper" that I have at home.

    Thanks,
    Gary
     
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    948
    in case anyone wanted to see the coupling portion of the circuit board. Mitutoyo digital depth gage in repair. dirt and grit gets between the board and the slide rail and acts like sand paper. gotta keep em clean and dry. IMAG0382.jpg n

    IMAG0383.jpg
     
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