Changing Fuse of a Digital Multimeter

Discussion in 'The Projects Forum' started by MMH, Mar 27, 2013.

  1. MMH

    Thread Starter Member

    Feb 8, 2013
    143
    4
    Hello there!!

    I have a Victor 81D which suddenly stopped working while measuring the rectified Voltage from A transformer(301v DC).While it was showing the result, it made a "Tick" sound and turned off. I replaced the batteries, but it still wont turn on. I think the problem is with the fuse. I tested the 250v 10A fuse and it is all right. But according to the meter, there is another 400mA fuse somewhere. When I opened the case, I saw Three PTC like things. On the circuit board one is labelled "PTC", one "Fuse 2" and the third "VRC". I found out that there is a short in the fuse which is normal(though I an Not sure whether the short is from another place in the circuit board). How will I replace it or is it that some other component needs to be replaced??
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I would post a photo of the board and fuses. Perhaps someone will recognize it and be able to help. And I would get a mod to move this thread to the general electronics forum where it might get more notice (this is not really a project).



    Are you certain it is just the fuse? There is a chance that you blew something else out before the fuse had a chance to go. Look around for any bad components. Post that pic because it is amazing what some folks can pick out around here. as blown parts.
     
  3. WBahn

    Moderator

    Mar 31, 2012
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    Look at the documentation or, if you don't still have that, look at the faceplate of the meter probably near where the probes are connected and see what it says about the maximum DC voltage that the meter is rated for.

    That will give us some hints about what to look at first.
     
  4. MMH

    Thread Starter Member

    Feb 8, 2013
    143
    4
    Thanks for answering!!

    It says that The MAX voltage is 600v (Oops, I have measured 1800v before). I will soon take a pic of that and post it here.
     
  5. WBahn

    Moderator

    Mar 31, 2012
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    You may have overstressed it with the 1800V and now the 300V was just too much for it.

    It's hard to fuse something for just voltage. The fuses in most meters only comes into play for the current ranges and, often, the top current range is unfused altogether.
     
  6. MMH

    Thread Starter Member

    Feb 8, 2013
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    Here are the pictures:
     
  7. MMH

    Thread Starter Member

    Feb 8, 2013
    143
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    There are some more:
     
  8. MMH

    Thread Starter Member

    Feb 8, 2013
    143
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    AND some More:
     
  9. MMH

    Thread Starter Member

    Feb 8, 2013
    143
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    Finally, it ends...
     
  10. MMH

    Thread Starter Member

    Feb 8, 2013
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    So spinnaker. I have posted images from all aspects. Now, is it easier for you guys to recognize the fault? If not tell me what to do next.
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    When you say the meter stopped working do you mean there is nothing being displayed, i.e. the LCD is completely blank?

    When the current limiting fuse blows, meters are normally still operable on the other functions.
     
  12. MMH

    Thread Starter Member

    Feb 8, 2013
    143
    4
    Yeah, there is nothing being displayed on the DMM, no matter where the dial is. So, what is blown out?? Can you identify the fault from the pictures??
     
  13. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    No way to no for sure but it certainly won't get so;ved without them.
     
  14. MMH

    Thread Starter Member

    Feb 8, 2013
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    Thanks for answering!!

    But what did you mean by "No way to no for sure but it certainly won't get so;ved without them??"
     
  15. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Exactly what it means. If no one can see what you have then how can they even begin to help?
     
  16. MrChips

    Moderator

    Oct 2, 2009
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    I think if there is nothing on the LCD then it's junk.
     
  17. MMH

    Thread Starter Member

    Feb 8, 2013
    143
    4
    Thanks for answer!!

    So, does it mean that there isn't any way to fix it?? If I need to do something else, please inform me.
     
  18. MMH

    Thread Starter Member

    Feb 8, 2013
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    Hello, so......
     
  19. WBahn

    Moderator

    Mar 31, 2012
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    So you probably need to buy a new meter. The one you have may or may not be repairable, but the ability to troubleshoot it over the internet is very limited. Someone would need to make circuit by circuit checks and, without good schematics, that is very difficult. You might throw it in a draw as a future project once you have enough experience and skill to tackle it and you want to do it as a challenge. But as it stands the troubleshooting cost for someone else to spend their time doing it will outstrip the cost of a new meter almost immediately.
     
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