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Neovo f-419 Power but 1 second of picture

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    #21
    Re: Neovo f-419 Power but 1 second of picture

    Originally posted by kc8adu View Post
    i have seen them further apart than that and still work.
    look to lamps.
    You and budm bring a valid observation that I never considered before. For future posts, I will have people check the ccfls in addition to suspicious transformer readings.
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      #22
      Re: Neovo f-419 Power but 1 second of picture

      A 3% difference in resistance between Inverter Transformer secondaries, has always been stated on here to be the 'rule of thumb' to decide if one is faulty or not.However I have seen up to 10% difference and still working fine.Perhaps it is dependant on particular models or associated circuitry,but certainly removing them from circuit and testing may well be helpful.When initially faced with a '2 secs to Black ' symptom, my first check is ALWAYS to test using a good spare Backlight, as its usually an easy thing to do just by taking the case off.But of course,everyone has there own ways, and not everyone always has a spare backlight handy.

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        #23
        Re: Neovo f-419 Power but 1 second of picture

        Originally posted by Rtech View Post
        When initially faced with a '2 secs to Black ' symptom, my first check is ALWAYS to test using a good spare Backlight, as its usually an easy thing to do just by taking the case off.But of course,everyone has there own ways, and not everyone always has a spare backlight handy.
        I find that checking resistance is the easiest for most people. As you pointed out, not everyone has a spare backlight especially if they are "one time" DIY fixers.
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          #24
          Re: Neovo f-419 Power but 1 second of picture

          Originally posted by Rtech View Post
          A 3% difference in resistance between Inverter Transformer secondaries, has always been stated on here to be the 'rule of thumb' to decide if one is faulty or not.
          PlainBill came up with the 3% a while back and explains it in this post.

          https://www.badcaps.net/forum/showpo...7&postcount=18

          So that is the number I have always quoted.

          I think I have also seen other people (tom66 or budm) suggest 5%.

          It is obviously easy if the reading were 0L or out of range.

          However I have seen up to 10% difference and still working fine.
          We have seen cases where the inverter transformer was barely within the 3% range and found to be root cause. I'll modify the troubleshooting guide to reflect the possible variations in percentages in the next revision.
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            #25
            Re: Neovo f-419 Power but 1 second of picture

            Well I always go by that rule - what we need is statistics - no one I have ever advised to buy a transformer has ever come back and said what a waste of money- the lamps had gone. I have seen considerably more people abandoning a project or increasing their outlay because they dont have the ability/ patience/ luck to swap out the bulbs.
            Having said that I believe most posters are asked to test lamps and transformers.
            For me, while they are photographing the board they can test the transformers it is one of the easiest tests and if it fails the next step is check the bulbs/wiring so that they dont end up buying both which will for a small monitor be more than a working monitor.

            I dont believe any of this is an exact science Just changing leads around top to bottom can bring a backlights back on.
            Last edited by selldoor; 05-27-2012, 02:59 PM.
            Please upload pictures using attachment function when ask for help on the repair
            http://www.badcaps.net/forum/showthread.php?t=39740

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