KC Micro Tronix
Member
This is by far the worst backlight I have ever fought!
it came in for no backlight water damage. Very slight water damage around C7793 and WX7720. Neither appeared to require rework.
Failure mode 1 Comes on then fades away after a 1 second. Voltage on Cathode of D7701 just slowly fades and screen is black. 22v, 17v, 16v after several seconds.
Failure mode 2 Back light does not even come on. 8v on D7701 cathode.
Failure mode 3 (works fine. Not a failure at all)
Testing / repairs done so far.
Diode test to D7701 cathode is .576 "perfect"
Flex board test "no change"
Thermal board test (hot / cold) "no change"
Feedback XW7720 was reworked. (and tested by soldering on to pad 5 on U7701 while it was removed and resistance testing while flexing board).
U7701 ( 2 times) "all resistors in this area were checked for proper values"
J830 LVDS connector (R7717-R7722 values verified)
C7796, C7797, C7799, C7712, C7713
D7701
Q7706
Q7707
Ran jumper to VIA and it fixed nothing! Failure mode 1 persists.
isolated VIA on both sides from D7701 & U7701. Worked perfect the first try then entered failure mode 1!
Ran jumper from U7701 LCDBKLT_BOOST to anode of D7701 failure mode 1.
it came in for no backlight water damage. Very slight water damage around C7793 and WX7720. Neither appeared to require rework.
Failure mode 1 Comes on then fades away after a 1 second. Voltage on Cathode of D7701 just slowly fades and screen is black. 22v, 17v, 16v after several seconds.
Failure mode 2 Back light does not even come on. 8v on D7701 cathode.
Failure mode 3 (works fine. Not a failure at all)
Testing / repairs done so far.
Diode test to D7701 cathode is .576 "perfect"
Flex board test "no change"
Thermal board test (hot / cold) "no change"
Feedback XW7720 was reworked. (and tested by soldering on to pad 5 on U7701 while it was removed and resistance testing while flexing board).
U7701 ( 2 times) "all resistors in this area were checked for proper values"
J830 LVDS connector (R7717-R7722 values verified)
C7796, C7797, C7799, C7712, C7713
D7701
Q7706
Q7707
Ran jumper to VIA and it fixed nothing! Failure mode 1 persists.
isolated VIA on both sides from D7701 & U7701. Worked perfect the first try then entered failure mode 1!
Ran jumper from U7701 LCDBKLT_BOOST to anode of D7701 failure mode 1.
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