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resistor blown frequently

Discussion in 'Troubleshooting and Repair' started by ngzek, Aug 24, 2015.

  1. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    22lg30r LCD tv power supply big resistor(may be start resistor i am not sure) located near rectifier is blown frequently. Please help
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    Lucky resistor.

    how quickly do you blow it? Does it happen as soon as you turn it on, or does it spend some time?

    If it doesn't come and go in a heated rush, do you hear any music or see any visions?

    Does it smoke afterwards?

    Enquiring minds need to know...
     
    Arouse1973 and Martaine2005 like this.
  3. shrtrnd

    shrtrnd

    3,671
    453
    Jan 15, 2010
    That blue component is a varistor, which is supposed to absorb large voltage spikes.
    The designers obviously expected initial in-rush voltage spikes, and that was their effort to deal with them.
    If your TV is otherwise working, I suspect other components in the circuit are wearing-out through age, and the voltage/current spikes are increasing.
    I'd take a look at what else is in-line with your resistor/varistor, and try to determine the cause.
     
  4. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    Steve it last for four five days, it burns with smoke and flame.
     
  5. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    Thanks Shrtrnd sure I'll do that thank you friends
     
  6. Martaine2005

    Martaine2005

    2,394
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    May 12, 2015
    Definitely.

    Martin
     
  7. Colin Mitchell

    Colin Mitchell

    1,419
    314
    Aug 31, 2014
    What is the value of the resistor?
     
  8. ngzek

    ngzek

    26
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    Aug 4, 2015
    Varistor value was not written but resistor value is 47 ohms. Its only 4yrs old tv.
     
  9. Colin Mitchell

    Colin Mitchell

    1,419
    314
    Aug 31, 2014
    You have to work out if it is metal film or carbon.
    Metal film will be say 1 watt and carbon will be 0.5 watt.
    You can do a couple of things.
    If it is metal film, use 2 x 22R 1 watt metal film in series.
    Or 4 x 47R carbon in series parallel.
     
  10. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    Okay I am trying to idendify its metal or carbon. Colin Mitchell may you please explain somemore detail about 2 x 22R 1 watt metal film in series.
    Or 4 x 47R carbon in series parallel.
     
  11. Colin Mitchell

    Colin Mitchell

    1,419
    314
    Aug 31, 2014
    Is the resistor in series with that blue thing?
    Is the resistor ORIGINAL
     
  12. ngzek

    ngzek

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    Aug 4, 2015
    No its not the original. It was damaged completely. Yes blue one( may be varistor) is connected in series with the resistor. I cannot find its schematics so I tried a rough copy from the board which I have attached below.
     

    Attached Files:

    • NG.jpg
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  13. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    Firstly you say they are in series and now you draw them in parallel.

    Nothing is making any sense.
     
  14. ngzek

    ngzek

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    Aug 4, 2015
    Oh I am too late to edit. Its my confusion between parallel and series. sorry its paraller not series.
     
  15. shrtrnd

    shrtrnd

    3,671
    453
    Jan 15, 2010
    I think what Colin is trying to get you to understand, is that because you already replaced your resistor, you may have replaced it with one that has the same resistance, but does not have the original wattage capability.
    If that is true, your resistor keeps burning-up, because it can't handle the wattage.
    You may not know the composition of the original resistor (what it's made out of), or that of the replacement resistor.
    Logically then, it is possible your resistor won't burn-up anymore if you replace it with a resistor capable of handling the original wattage, or something bigger (wattage, not resistance).
    I think Colin is just trying to help you determine if a low-wattage resistor alone, is the source of your problem.
     
  16. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    The original resistor and the varistor were damaged completely and I cannot find this lcd tv model 22lg30r's schematics and components data. I use to replace with most probable value suggested by local technician but it keeps burning.
     
  17. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    Thank you Shrtrnd
     
  18. hevans1944

    hevans1944 Hop - AC8NS

    4,247
    1,997
    Jun 21, 2012
    Two 22 Ω resistors in series is 44 Ω, close enough to the 47 Ω that is burning up, but twice the wattage capability of a single resistor.
    Two 47 Ω resistors in series, paralleled with another two 47 Ω resistors in series, will be 47 Ω but with four times the wattage capability of a single 47 Ω resistor.
     
  19. Old Steve

    Old Steve

    734
    169
    Jul 23, 2015
    Did you replace the MOV? If it's dead, the resistor will most likely keep burning up.

    I found the service manual, but in their wisdom they don't include the PSU schematic, just everything else.
    Here's the manual, FWIW, (you'll need to download the free DejaVu viewer to see it though):-
    http://elektrotanya.com/lg_22lg30r_ch_lp81k_sm.djvu/download.html
     
  20. ngzek

    ngzek

    26
    0
    Aug 4, 2015
    Hevans 1944 thank very much now I got the full meaning. Iam not good in electronics language.
     
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