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Non Repairable Of UNITY 830D Multimeter

By on September 10, 2021
multimeter repair

I was at a bike service center for routine servicing of my Bike. In conversation about new technology trend of bike. Suddenly mechanic remembered that he has one multimeter which was damaged by one of his helper & request me to check the multimeter which is not working properly.

multimeter repair

I took multimeter on my hand for testing. it does not respond to reading while testing any range with use of multimeter probe so I took the multimeter with me for further testing.

While tested the multimeter on voltage range it keeps on changing values on the screen without test probe connected and on another range it shows -1 sign. So for further inspection I opened the multimeter.

multimeter circuit board repair

There is no component on back side of the circuit. On visual inspection I found 1 ohm resistor discolored.

burnt smd resistor

So I checked it in ohm mode with my multimeter it is showing the perfect reading. For reconfirming it out of the circuit I have desoldered this SMD resistor and checked again it shows perfect value that means this resistor seems Ok .but I did not end up here I took 1 Ohm 1/4w carbon resistor soldered it in place of that smd and powered the multimeter still problem is same. (Just having doubt that SMD may not working under the load).

normal resistor replace smd resistor

Now without wasting more time I start testing all the components one by one. One resistor pack of 1MΩ giving some falls reading. So I removed it from the circuit and checked again.

termination resistor

bad ic in multimeter

This resistor pack is showing perfect reading out of the circuit. On tracing I found all 4 output side of this resistor are going to that controller IC.  Tested rest of the components all are read perfect value 1MΩ as per the code marked on.

Now there are no more components to check hence I concluded this job as non repairable because it is not possible to check this type of IC or replace hence considering IC itself is bad & this multimeter is non repairable……….

Some new mechanics are not familiar with the operating of this type of device. Bikes and other vehicles using  battery of high current capacity so while troubleshooting of wiring mechanic may be forgot to disconnect the battery supply wire first and here he has damaged the meter by selecting wrong range to check live wire.

For reference I am sharing coding and value of SMD resistors for reference. Just enlarge the following photo and see the value marked on……..

value marked on circuit board

Despite being cheap I would recommend this type of multimeter to newbie/DIY & Hobbyist persons these meters are available around 3$.if you have budget then choose as per advance technology with various useful options as per your requirement.

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.

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Note: You can check his previous repair articles on Camphor Diffuser and Capacitor Discharge Tool

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6 Comments

  1. Anwar Y Shiekh

    September 10, 2021 at 8:05 pm

    Sometimes we forget about repairs that are not possible and only post those that are; so it is good to be reminded that not all repairs end in success.

    Likes(5)Dislikes(0)
    • Yogesh Panchal

      September 12, 2021 at 3:53 pm

      Anwar Y shiekh,
      How you conclude repair without diagnosis???, I did my best to repair the unit. I shared here because if someone needs circuit layout and SMD Component location with value.this may helpful to them to figure out the problem and newbie will learn the process how to troubleshoot and by this they can understand "that why not all repairs end in success".
      Thanks for your Comment.

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  2. Parasuraman S

    September 10, 2021 at 8:19 pm

    A creditable attempt and learning and that is what matters at last! Good job there, Yogesh!

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 12, 2021 at 3:57 pm

      Thank You! Sir,

      Likes(0)Dislikes(0)
  3. Albert van Bemmelen

    September 10, 2021 at 8:19 pm

    The used processor controller is probably a ICL 7106 or comparable chip. See here.
    Or if it really use 44 pins it can be a chip like the 44 pins chip used in the DY-294 semiconductor tester. So replacing is possible like I did in the DY 294 repair!

    Likes(6)Dislikes(0)
    • Yogesh Panchal

      September 12, 2021 at 4:31 pm

      Albert, Thanks! for the Link.
      frankly Albert i assumed some resistor may out of the value but it was not.
      and secondly i can get 3 same new meters in the cost of new IC.that's why
      concluded the repair by taking note of all SMD resistor Value and shared here for reference whoever needs the detail.

      Likes(2)Dislikes(0)

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