Non Repairable Of UNITY 830D Multimeter
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.
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.
There is no component on back side of the circuit. On visual inspection I found 1 ohm resistor discolored.
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).
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.
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……..
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