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problem in DT-9205A multimeter

Discussion in 'Troubleshooting and Repair' started by Mohamed Gamal Mazen, Jun 8, 2019.

  1. Mohamed Gamal Mazen

    Mohamed Gamal Mazen

    6
    0
    Jun 8, 2019
    Hi guys i have this multimeter. its problem after replacing the battery all measuring choices gives -1 with the low battery indication sign and i have tried another battery but its doing the same thing. so if the schematic i have seen on the internet for this multimeter was right this means that icl7106 is damaged or there is another problem ? please help
     
  2. caps

    caps

    155
    8
    Jul 29, 2018
    There may be short circuits in the multimeter circuit. Pay attention to the 74HC14D chip.
     
  3. caps

    caps

    155
    8
    Jul 29, 2018
    If there is another multimeter,check the new battery.
     
  4. Mohamed Gamal Mazen

    Mohamed Gamal Mazen

    6
    0
    Jun 8, 2019
    I have checked it its working ,i'm going to check the schmitt inverter
     
  5. caps

    caps

    155
    8
    Jul 29, 2018
    At the same time, check the quality of the contacts of the display cable and the voltage between the com of the multimeter and the + battery. There should be about 3V.
     
  6. Mohamed Gamal Mazen

    Mohamed Gamal Mazen

    6
    0
    Jun 8, 2019
    i have checked the voltage between the com of multimeter and the + battery when the switch is closed is about 0.74 V and when it's opened the voltage is 7.68 V what i have to check now ?
     
  7. Mohamed Gamal Mazen

    Mohamed Gamal Mazen

    6
    0
    Jun 8, 2019
    after some check i found Q4 and Q5 transistors j3 (s9013) are shorted in emitter and collector is this a reason for this problem ?
     
  8. caps

    caps

    155
    8
    Jul 29, 2018
    This is checked at the 20mA switch position.
    The power of the multimeter is turned off. At the switch position of 200 mV, the input resistance between the com and v terminals should be 1 MΩ.
     
    Last edited: Jun 9, 2019
  9. Mohamed Gamal Mazen

    Mohamed Gamal Mazen

    6
    0
    Jun 8, 2019
    yes it's 1 MΩ but forgive me i still don't understand what to do ?
     
  10. caps

    caps

    155
    8
    Jul 29, 2018
    What is the switch position?
     
  11. Mohamed Gamal Mazen

    Mohamed Gamal Mazen

    6
    0
    Jun 8, 2019
    every position
     
  12. caps

    caps

    155
    8
    Jul 29, 2018
    About transistors.How can they have a short circuit if you just replaced the battery.
    To answer your question, it is better to look at the diagram.
    Either you take a photo of your board, or look for a diagram of your version of the multimeter.
     
  13. caps

    caps

    155
    8
    Jul 29, 2018
    Then it is not very good.
     
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