ICL 7107 digital voltmeter helps needed

Discussion in 'The Projects Forum' started by williame.newtist, Jun 26, 2012.

  1. williame.newtist

    Thread Starter New Member

    Jun 26, 2012
    1
    0
    Hello,

    I'm building ICL 7107 digital voltmeter with 200mV full scale as Figure 12 (page 11) on http://www.intersil.com/data/fn/fn3082.pdf
    Here is the problem I'm facing:
    it shows random numbers, sometimes showing 1666, and it has no effects even when I try to calibrate by adjusting the potentiometer or shorting the inputs pins the values remain the same. Even the whole potentiometer is removed the value still stay there!
    I have read through the datasheet and couldn't find any possible defects of the components that might have caused this.:confused:
    I have tried to replace the 0.1 microfarad capacitor with 1 microfarad but the problem remains the same and I did check the connection trace.
    So, I was wondering if you have any idea? and Thanks in advance, that really means a lot to me. :)

    William
     
  2. Pich

    Active Member

    Mar 11, 2008
    119
    4
    Make shure that all your common connected together. Do have a circuit you can share?
     
  3. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    Take a picture of your circuit board or breadboard. May be we can help you spot the problems.

    Allen
     
    Last edited: Jun 26, 2012
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Those chips are easily blown up, I have a meter that uses them. I recall random numbers was the symptom of a blown IC.
     
  5. rfredel

    New Member

    Jan 23, 2011
    25
    3
    Hello William,

    I think also, that you have a dead IC.

    These ICs are very sensitive to static electricity. :mad:

    Normaly I don't care against static electricity to MOS-ICs, but after killing two of this voltmeter and counter ICs I really take care of proper handling and grounding during installation. :rolleyes:

    Regards

    Rainer


    PS: Sorry, if my English is not so good.
     
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