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simpson analog meter wont zero up

Discussion in 'Repairing Electronics' started by Bmerboy98, Dec 7, 2008.

  1. Bmerboy98

    Bmerboy98 New Member

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    My simpson meter ..its a 260 (yellow case) analog meter

    doesn't zero up on ohms function ,,the needle reading stays towards the center of the scale and cant be zeroed up on the ohms function..batteries, fuses have been replaced ..

    the needle goes to zero on voltage scales

    could be a resistor? but i have no idea which one to replace to correct this

    Meters are used to teach children and i have several with this problem so help would be greatly appreciated



    thanks
     
  2. Willbe

    Willbe New Member

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    Post a schematic; it could be an open resistor or bad solder joint.
     
    Last edited: Dec 7, 2008
  3. saturn1bguy

    saturn1bguy New Member

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    I know one of the list guys (many perhaps?) is the proud owner of a Simpson 260. Perhaps he'll chime in...

    You say you replaced the battery. Did you actually measure to make sure it was good?
     
  4. dave

    Dave New Member

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  5. Bmerboy98

    Bmerboy98 New Member

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    im going to try another d battery tomorow...

    the problem is that the needle reads to abt 1/3 of the scale and stays there on any ohms scale
     
  6. Bmerboy98

    Bmerboy98 New Member

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    i dont have a schematic
     
  7. Leftyretro

    Leftyretro New Member

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    And check for contact corrosion on the battery terminals.
     
  8. Rolf

    Rolf Member

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    Check the resistor in series with the Ohms zero trim pot, sounds like it has changed value. You might be able to experiment and find the correct value. Or measure it on a good meter. These two resistors are the only ones that docent change when you change resistor ranges, so it stands to reason that it might be the problem.
     
  9. on1aag

    on1aag New Member

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    Hi Bmerboy98,

    There seem to be a lot of versions of the Simpson 260
    but I found one with a yellow case and there's a
    schematic at page 32 of the manual.

    on1aag.
     

    Attached Files:

  10. mneary

    mneary New Member

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    Did you change both batteries? On some of the older Simpsons, the 9V battery is very similar in size and shape to a "C" cell. You may have to adapt the connections to the modern 9V battery
     
  11. Willbe

    Willbe New Member

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    According the schematic the same battery is used for the Rx1 and Rx100 scale, so see if you also have zeroing trouble on the Rx100 scale.
    Does the meter work on other ranges?
    The 1.5v batt. neg. goes to the meter movement negative through R2. I'd first look at the value of R16. This 11 ohm resistor corresponds to the center reading of 12 ohms.
    The only other resistors involved in Rx1 are R17-R21. If you take readings in this network we can probably troubleshoot it down to a single resistor.

    With a 50 uA meter at 250mV the movement itself is 5kohm.
     
    Last edited: Dec 8, 2008
  12. GonzoEngineer

    GonzoEngineer New Member

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    Every Simpson Analog Meter that had this symptom was the same problem.

    Bad batteries!..double check the batteries.....both of them!

    If those are OK, did a student perhaps mess with the meter zero adjust. It is the plastic, slotted screw in the center of the lower part of the meter movement itself. My son mesed with mine once many years ago drove mu nuts for about an hour.

    If these don't fix the problem, time to open it up and check it against the schematic.
     
    Last edited: Dec 22, 2008

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