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Discussion in 'General Electronics Discussion' started by S1lence1, Dec 17, 2016.

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  1. S1lence1

    S1lence1

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    Dec 17, 2016
    I went to the local electronics store today in search of a 1KV 103pF capacitor and was informed that a 500v 103 would work fine in it's place in my LCD tv. I'm still very new at circuitry but this just doesn't sound right to me and im especially suspicious considering they were out of stock on the 1kv.

    Any input from a person knowledgeable in this would be greatly appreciated.
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009

    That wasn't good advice, always use the stated voltage or a higher voltage rating
     
    chopnhack likes this.
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    where in the circuit is this capacitor ?
    why do you think it is faulty ?
    show us a photo of the area of the PCB where that cap is
     
  4. BobK

    BobK

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    Jan 5, 2010
    I would be very surprised to find any voltage above 500V in an LCD TV.

    Bob
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    have you not worked on LCD TV's ?

    maybe not ..... most, if not all, have voltages of 1kV some have more
    Usually in the inverter output section

    this is why I asked for the info that I did ;)


    Dave

    [ the newer LCD TV's that use LEDs for backlight illumination don't use that higher voltage ]
     
    Last edited: Dec 17, 2016
  6. Audioguru

    Audioguru

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    Sep 24, 2016
    I think a value of "103pF" is fishy. It is probably 10,000pF or 10nF (0.01μF).
     
    Arouse1973 likes this.
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    yeah, he didn't know how to read the value ;) ..... 103 (10nF) is a reasonably common value in the inverter stage ... it's also a value and voltage rating often used in power rail decoupling around the SMPS
     
  8. S1lence1

    S1lence1

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    Dec 17, 2016
    Best I can take with my android, the burned side of the capacitor makes me think that the loud "POP" that happened before the shutdown is a damaged capacitor.

    So what you're saying is that it's a bad idea to put in the 500v he sold me, We're having some really bad weather here and I wanted to be able to watch for freeze warnings in TWC. Board1.jpg Cap1.jpg
     
  9. BobK

    BobK

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    Ah yes, I forgot that they used to have fluorescent backlights. Never had one of those, I went for plasma.

    Bob
     
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    hi ya

    I don't see that cap as having gone bang unless there is a crack running along its edge in the area of the darkening

    it is very unusual for those caps to fail, it could possibly indicate a fault elsewhere.
    if some electronics shop locally cant supply them, you can try mouser, digi-key or if you really need to eBay. buy more than one


    that's what I said ;) :)

    This cap is in the SMPS ( switch mode power supply) section, you can see several others around there

    the other HV caps are those 4 in the top left corner of your first pic ... they are the ones in the inverter output section I mentioned in another post
    they could easily have 3kV ratings written on them. The inverter feeds HV AC to the fluoro tubes that backlight the LCD panel


    Dave
     
    Last edited: Dec 18, 2016
  11. davenn

    davenn Moderator

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    Sep 5, 2009

    if you are currently using a LCD monitor for your computer, there's a high probability it's fluoro back lit :)
     
  12. davenn

    davenn Moderator

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    Sep 5, 2009
    you may have read AG and my comments on the capacitor value you wrote

    when you see a say .... 103, 101 or say 222, that is the value in pF so you don't add pF after it. It's read like this ...

    103 = 10,000 pF = 10 nF = 0.01uF
    101 = 100 pF = 0.1 nF
    222 = 2200 pF= 2.2 nF = 0.022uF

    you can see from those examples how the 3rd digit is the multiplier digit. It tells you how many zeros to ass to the first two digits
     
  13. S1lence1

    S1lence1

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    Dec 17, 2016

    Davenn thank you for the clarification on this but as an extreme beginner things like "103 = 10,000 pF = 10 nF = 0.01uF" will take some time and lot more background for me to grasp. I did however notice that when searching for these parts each individual seller seems to have their own criteria on what the specific numbers on the part should be and even more frustrating for me was once I had determined the numbers 103, 1kv and swc on the part in my unit I found out there are .1, .01, and .001 versions of it and NO ONE seems to want to carry the .01 except vendors from mainland china.

    My bottom line is I want my TV to work and don't want to pay 200 bucks for someone to solder in a part that costs betwen 1-3 dollars. It's like the mechanic you take your car to who charges you 50 bucks to turn a screw, he's not charging you for the actual act of turning it, he's charging you for knowing which screw and how far to turn it.

    The advice you guys give me saves me from getting expensively screwed and I thank you for it.
     
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