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toshiba 65ul2163 dbl no backlights NOT BACKLIGHTS?

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    #1

    toshiba 65ul2163 dbl no backlights NOT BACKLIGHTS?

    Hi this vestel 65in tv had classic no backlights ,so nothing new there!
    tested with b/l tester and the b/l seemed to be fine
    so investigated psu 17ips72 (on this 65inch there are 3 fets and control iv type DB83630P)
    did a thorough check on b/l circuit all ok .
    When i tried again with b/l tester all ok .but then when i reinstalled psu all worked fine ,
    could there be a component on psu that is causing the protection mode to stop b/l
    .maybee causing it to be too sensitive?
    it seems to me if the b/l have been on with my tester ,within a couple of minutes if i reconnect the psu they will work fine

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    #2
    Backlights can be funky. I get tvs with BLs out from customers, turn on and they work. Even for 2-3 days and test fine. Doesn't always rule them out. They eventually go out again and I can then make them test bad. Just throwing that out there before you decide they are just good.

    Pictures of PSU/connectors would help also

    Comment

      #3
      its still a work in progress
      i have reduced the backlight current ,by increasing the fet source pin resistance
      .it had 5 resistors in parallel .47 ohm
      i simply removed two of these as an experiment .now the tv b/l come on as normal
      i was given the tv so its fine to experiment

      Comment

        #4
        The 17IPS72 has a OB3363QP backlight driver, so the backlight current is regulated by 5 pin. ISET (when the resistance of this series resistor chain increases, the current to the LEDs drops).
        Attached Files

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          #5
          thanks lotas and eazybone for your reply
          .i will keep it running on test ,
          the original owner had the b/l at 100%
          reducing it to 50 % and removing two of the parallel resistors (increasing the resistance )
          tv still gives good picture

          Comment

            #6
            So what you have is probably one or more weak backlights, since lowering the current they stay on. It may live for a long time like that but if it does the same you know where to look.

            Comment

              #7
              exactly. i have replaced many b/l over the years
              and sometimes its obvious that the strips have had a hard life as they are discolured
              this one they all looked fine ,but only time will tell

              Comment

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