unidentified SMD components

Discussion in 'General Electronics Chat' started by melrel, Apr 7, 2011.

  1. melrel

    Thread Starter New Member

    Apr 1, 2011
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    Hi guys. I am new to electronics having just retired. Unfortunately I had an accident whilst removing a component from a Z-Sus board in a plasma TV. The component I destroyed, I think, is an SMD capacitor. I measured it and it fits into the category of an 0805. There are no markings so how do you know the capacitance, voltage, wattage etc? It has an ESR of 1.5 ohm. I bought a SMD tweezer DMM but it wont measure nf. and I can't find a schematic for this board anywhere. Its from an LG 42PX5D. Board number 6871QZH056B. Would really appreciate any info on this.
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
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    PackratKing likes this.
  3. melrel

    Thread Starter New Member

    Apr 1, 2011
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    Hey, thanks for all your efforts with this. It's a step forward for me although I don't pretend to understand everything here, but I'll endeavour. Best wishes Robert
     
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Doesn't the ESR depend on the test frequency and exact shape of the test waveform?

    I really think to measure capacitance you should use a capacitance meter!

    If you don't have a cap meter you could do something like use the cap in a 555 timer circuit (look at the freq on the 'scope) and compare to other test caps in that same circuit. It shouldn't take too long to work out its value. :)
     
  5. Jotto

    Member

    Apr 1, 2011
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    Is this a ceramic cap? I will look to see if I can find a drawing on this unit. I have the manual if you will tell me what the designator is I can tell you the value.

    Or I have the complete service manual if you want it.
     
    Last edited: Apr 8, 2011
  6. melrel

    Thread Starter New Member

    Apr 1, 2011
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    Thanks The R_B. As far as I understand the ESR does depend on the test frequency but I guess that test frequency is unique to the design of the meter and the ESR vs voltage scale is worked out accordingly. I'll have a go at what you suggest but even if I know the cap value, how do I know the voltage and wattage to specify when ordering. This capacitor is about half the size of an ant!!!
     
  7. melrel

    Thread Starter New Member

    Apr 1, 2011
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    Thanks Jotto for this. I'm going to send you some photos of this capacitor. As I said to The_RB, it's about half the size of an ant. I think its ceramic and its black in colour. Does your service manual provide a schematic for the Z-Sus board? If so, I would be grateful for it. Appreciate your help. Robert
     
  8. melrel

    Thread Starter New Member

    Apr 1, 2011
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    destroyed caps.jpg

    Hi
    Here's a photo of the line of caps I am talking about. You can see I destroyed the last three. The all have the same ESR. Robert
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    They are connecting the ground plane.

    They are likely 0.1uf caps to filter power supply noise.

    Known as typical bypass or decoupling caps.
     
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