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Samsung LE40M87BD 40" LCD TV Clicks but won't turn on

Discussion in 'Audio Visual' started by IJWS15, 23 Mar 2011.

  1. Mickymoody

    Mickymoody

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    As long as the 2200 micro farad is good, overrating them is even better. Why the manufacturers use the bare minimum is strange? Obviously costs.

    Nice one.
     
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  3. Sam Gangee

    Sam Gangee

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    Actually, that's slightly worrying. In my experience, better (more reliable) capacitors will always be larger - especially if they have a higher voltage rating or capacitance. Your Maplin capacitors may not last long.

    See http://www.satcure.co.uk/accs/television_capacitors.htm
     
  4. Mickymoody

    Mickymoody

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  5. Sam Gangee

    Sam Gangee

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    Fair comment. So what is the ESR of the Maplin capacitor?
     
  6. Mickymoody

    Mickymoody

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    Without the technical specs, or physically testing the caps, it's impossible to guess, versus the OE spec that was fitted. I doubt that the ESR is listed, as it would vary from each manufacture?
     
  7. Sam Gangee

    Sam Gangee

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    Maplin should know. If a seller can't provide the ESR value then it's likely that it's high, meaning that it's a "general purpose" electrolytic, which may not last long in a switch mode PSU. Typically, the value will be 0.03 Ohms or lower at 100kHz.
     
  8. Mickymoody

    Mickymoody

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    I thought high ESR is good? But was wrong, good call.
     
  9. Sam Gangee

    Sam Gangee

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    The problem with using incorrect capacitors is that the PSU may appear to function perfectly at first but you may notice a little interference on the picture, which gradually becomes worse. This occurs because a capacitor with too high an ESR allows short-duration high-voltage spikes to escape on the "DC" supply lines, causing the interference. The picture can be affected in different ways, including a slight "graininess". The interference can also be superimposed on the tuning voltage, causing problems with tuning and some quite weird effects.

    The capacitors will run warm, or even quite hot to the touch, and the problems will become worse.

    There's a good article about ESR here:
    http://members.ozemail.com.au/~bobpar/esrtext.htm

    ESR is quite simple, by the way. It's just the impedance of the capacitor, which is usually measured at 100kHz for convenience. "Effective Series Resistance" is just a fancy term used to describe it.
     
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  11. gblades

    gblades

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    Marlin are pretty useless for specialised components such as these.
    They only do one range of high temperature capacitors which is the first thing to filter on when choosing replacements. They don't list a manufacturer or spec.
    If you didn't fit the high temperature caps then I would strip them out again and fit proper rated ones. If you did then they will probably be ok
     
  12. Sam Gangee

    Sam Gangee

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    Temperature rating doesn't matter per se but, certainly, any capacitor rated at less than 105°C will NOT have a low ESR value.

    Conversely, a 105°C rating does not by itself guarantee that you have a low ESR capacitor! The only way to be certain is to measure it or to see the written specification.
     
  13. Mickymoody

    Mickymoody

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    Because new components have been introduced, the whole set needs recalibrating.

    I think you mistake ESR for misunderstanding what it means? Electrical components are tested 'for convenience', for fun, I suppose?
     
  14. gblades

    gblades

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    Sams explanation sounds spot on to me. What do you disagree with?
     
  15. Sam Gangee

    Sam Gangee

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    I don't think he was disagreeing.

    (Actually, I don't understand what he means, at all. Which set of what needs recalibrating?)
     
  16. Sam Gangee

    Sam Gangee

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    Replacing the capacitors in a PSU brings it back to the original specification (or better - i.e. less ripple on the DC supplies). Nothing on the PSU should need to be adjusted. It is self-regulating - usually using a comparator and an accurate voltage reference source. There are no components in a PSU, apart from electrolytics, that have a limited life, provided that they were correctly specified in the design.

    We are well past the age of thermionic valves! (Although I'm old enough to be familiar with them!)
    See A Beginner's Guide
     
  17. IJWS15

    IJWS15

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    Just dug this out as son's TV, slightly later model, seems to be developing the same fault.

    Daughter's TV still going strong on the cheap Maplin capacitors.
     
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