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Faulty tv power

Discussion in 'Troubleshooting and Repair' started by Boo, Jan 2, 2016.

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  1. Boo

    Boo

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    Jan 2, 2016
    Hi guys,

    First time posting here, i've read the general guides and rules and will try to be as informative as possible.

    First id like to tell you that i'm not the typical electronics guy, i have a v good technical xp and usually find my way through simple electronics issues, for this i'm out of thought and would like to hear what you guys think.

    I have a tv that's my parents, im not sure how or why (neither do they) but it suddenly wouldn't turn on.

    -wont turn on as in no power at all, power led not wont even light.
    -I initially tested the power cable its fine
    -i opened the tv and found the main fuse burnt. Its a 15AL fuse.
    -i managed to replace it with a 10AL fuse (couldn't find a 15AL will get one on Monday)
    -i tried to turn it on, my ups APS system went off as soon as i turned the tv on.
    -i switched to regular power outside the APS
    -power the tv> it made my lights go dim for a sec as if its starting up but nothing really happened. Still off
    -new fuse (10AL) still ok

    The only unusual thing i could see is a unit labeled "R4" that is near the fuse, it has a vivid blackish spot on it but dosent seem like burnt. Ill post a pic in a min.

    Any thoughts are welcome
    Thanks guys
     
  2. Boo

    Boo

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    Jan 2, 2016
    So i just checked the APS, its fuse is burnt.

    Btw, no burn smell from anywhere in the board/s
     
  3. Martaine2005

    Martaine2005

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    May 12, 2015
    Fuses blowing would normally suggest a short.
    What is a "ups APS"?
    Sorry for silly question!

    Martin
     
  4. Boo

    Boo

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    Jan 2, 2016
    Thanks for the reply and no worries, its supposed to be a ups that has a automatic power system where normal electricity passes through and when power is out it starts providing from the batteries automatically.

    Must be a short, but if it has a short, shouldn't the tv fuse blow instead of the UPS?

    Thanks again
     

    Attached Files:

  5. Boo

    Boo

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    Jan 2, 2016
    Heres what the R4 "thing", sorry i dont know what its called. I couldnt tell if something's wrong with it.

    Anything i should test? I have a multimeter.
     

    Attached Files:

  6. Martaine2005

    Martaine2005

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    May 12, 2015
    Ah, a UPS..Uninteruptible power supply...
    So what is the APS..
     
  7. Gregorio Mandigma

    Gregorio Mandigma

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    Jan 2, 2016
    can you upload the picture of your tv
     
  8. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    R4 looks like an MOV or some kind of NTC or PTC. Instal a new fuse and remove R4. Then power up. See if you can see whats written on R4.
    Adam
     
  9. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    It doesnt have a picture, it wont power up :)
     
    Martaine2005 likes this.
  10. Martaine2005

    Martaine2005

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    May 12, 2015
    Mine?
    upload_2016-1-2_20-6-35.jpeg
     
  11. HellasTechn

    HellasTechn

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    It looks like a Varistor. Normally theese are in series with the fuse (right after it) to create a short circuit and blow the fuse if ac voltage goes too high (surge). Most times if they are not exploded they are ok !
     
  12. HellasTechn

    HellasTechn

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    Apr 14, 2013
    Arent NTC's and PTC's Thermistors ?
     
  13. Boo

    Boo

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    Jan 2, 2016
    this forum is active more than i thought! awesome!

    well here's the Thermistor? whatever it's called, as far as i can tell it's not blown, it has some black shade on it, anyway you're the experts so..
     

    Attached Files:

  14. Boo

    Boo

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    Jan 2, 2016
    and thanks a lot guys for all the replies :)

    btw i was powering up through a cable extension, i just tried hooking my laptop and baam! no power!! its either the extension that made the short (that's why the UPS fuse was blown) or could it be the TV has a short and blew the extension!?

    should i try the TV on another surge protector?
     
  15. HellasTechn

    HellasTechn

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    Apr 14, 2013
    Ok as i said before it is most probably a varistor, if you take a picture of the other side of the board to see how it is routed then i may be able to say.

    It could be due to a power surge (rise of voltage, varistor's voltage goes low and forces large ammount of current to blow the fuse and protect the psu).

    The fact that the new fuse is not blown makes me think that it may have been just a random incident. I guess you could check on an other power socket. I would prefere a fused one.
     
  16. Boo

    Boo

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    Jan 2, 2016
    just gave it a test again directly in wall plug, the 10A fuse blew up, i'm getting the 15A on Monday so will let you know
     
  17. davenn

    davenn Moderator

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    Sep 5, 2009
    NOOOOOOOOOOOOOOOOOOOOOOOOOOO

    you NEVER replace a correct rated fuse with a bigger one just because it blows ....
    well you do is you want bangs, showers of sparks, house fires etc

    You MUST find out why the fuse is blowing !!!!!!


    Dave
     
    Arouse1973 likes this.
  18. Martaine2005

    Martaine2005

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    May 12, 2015
    I think you mean a T3.15AL?
    It's a Time delayed, 3.15A (L) glass fuse!! DO NOT put a 15A fuse in it!
    It certainly looks like a MOV..(Metal Oxide Varistor). These are very common failure points due to electrical spikes/surges..That is there job to protect the rest of the circuit.

    Martin
     
  19. Martaine2005

    Martaine2005

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    May 12, 2015
    :p Again Dave.....Beat me...But his post is prettier!!
     
    Last edited: Jan 3, 2016
  20. davenn

    davenn Moderator

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    man alive ..... sometimes I really want to type masses of swear words as a response when I see posts like that
    instead I can only shake my head in disbelief :eek::rolleyes:
     
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