Checking ICL7107

Discussion in 'The Projects Forum' started by jj_alukkas, Apr 11, 2009.

  1. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    I made a voltmeter recently with ICL7107 and it worked fine while I was calibrating it.. Then I had it connected to a power supply and two times it worked well but yesterday it wouldnt switch on at all.. I found that the 7805 and 7905 regulators were giving only around 3.5v each which used to give 5v correctly in the beginning.. I cant find any problem in the transformer or rectifier but I get only 3.5v each.. Input to the regulators is 7v.. so I used another transformer and gave an input so now output is giving 5v each but my display shows a static number.. Its not dynamic.. Mostly shows 10.88 without load.. Is my IC blown off??? It doesnt move at all.. Connections are ok and how can I confirm before I buy a new IC??? Also what could have happd to the transformer??
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,652
    2,348
    Hello,

    Is tye oscillator running? This can be checked on pin 38.

    [​IMG]

    If the oscillator is not running the display is frozen.

    Greetings,
    Bertus
     
  3. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    How can I check that?? Dont have an oscilloscope.. anyway using multimeter?? Also If the display is frozen, can I reset it??
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,652
    2,348
    Hello,

    You could try to measure an AC voltage on pin 38.
    The amount you will measure is dependent on the duty cycle, but will be round 1/2 Vcc.

    You could also try to make a logic probe.
    http://www.electronics-circuit.com/basic_Logic Probe.html
    When both leds are burning the signal is pulsing.

    Greetings,
    Bertus
     
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