at first, tv wouldnt turn on at all. no backlight flash, nothing. ok maybe it had a flashing standby light. i cant remember....
i rushed in before taking notes. should have done sound test, mb test, other tests...
or if i did i should have wrote them down but i didnt.
i went straight to the backlights because with the LED tester i was able to see
right away that one of the two strings was open. (wouldn't light up)
there are only 4 wires going to the backlights. 2 black and 2 blue. blue is positive. black is negative. 2 strings, and ones not working.
thinking it would be a straightforward backlight repair (and nothing else wrong!), i opened the panel and
got to work. i found that all the LED's were actually lighting up fine except for one strip. but on that strip when i tested them individually they were all fine.
this puzzled me but eventually i noticed that there was a burnt trace leaving
one of the LEDs unconnected, thus making the whole strip open.
i repaired the trace with some wire, and now both sides (blue and black pairs) responded well to the
LED tester.
both of them using about 115v and lighting up nicely.
i jumped the gun again, and completely reassembled the TV when i should have left it apart to test the psu and backlight combo but i didnt.
once i got it back together and tested the psu and backlight by themselves, or with the mainboard connected i
was now getting a strobing backlight, and im pretty sure its crashing the
mainboard as well because when its connected i cant see any image at all when powering on.
when i leave the backlights diconnected, and all other boards connected normally and power the backlights seperately with the LED tester, i can see the picture is fine, the menu is fine. the LCD is fine, not cracked. the TV looks great, if only a little dark because only one string is being lit.
in this state, i unhooked the led tester from the backlights and plugged the
backlight connector into the PSU and immediately get the strobing light, and
the image that was on the screen gets corrupted in some weird way. and the tv would not respond to power off requests. i had to unplug it.
so what is going on here?
do i still have some kind of problem with my backlights even tho the tester
lights them up fine? i know budm told me the tester doesnt put out as much current as the
psu would, and some LEDS can light fine with the tester but fail under full
current...but how can i test for that? there must be something i can do besides opening this panel again!
voltages to the mb look fine to me
but then again i dont know everything about this board, and there arent any threads about it.
voltages, with MB and BL disconnected:
for the mb connector:
on the 13v pins im getting 12.65
others:
UD: 2.28v (no idea what UD is)
PWM_BLU: 3.24v (seems normal but i just dont know anymore)
PS_ON: 3.24v (ditto)
for the LED connector
im getting 401v on pin 1 and 2 and 0v on all others
(no idea how to know what to expect as normal V+ on these pins with no boards or LED connected, but 400v seems like enough?)
voltages with MB disconnected, BL connected: (while BL strobes, which i dont like to do for very long...is this damaging?)
on all the 13v pins im getting around 5v
and 0 on all the others except 1.6v on the PS_ON pin
on the LED connectors i get 113v on pins 1 and 2, and 0 on all the others.
the 113v seems in line with the 115v i was getting on the readout of the LED tester, but why does it fail?
i actually bought a replacement PSU because it was cheap (25$) and it has all the same voltages and does exactly the same thing as the original, except that when its by itself, the voltage one pin1 and 2 of the LED connector reads 420v instead of 401v
continuity between harness pins and connector pins for LED connector are good. pins are making contact with the wires.
kinda stumped here. really dont want to open the panel again
psu model:
L60H1_EHS BN44-00775A
BN4400775A
what is interesting to note here, is that the mainboard seems to be totally fine with having no backlights connected to the PSU, and if you can light the backlights some other way then you will have a nice tv, though i'd imagine the menu would no longer be able to control the backlight levels...
another thought (creepy) is that the mainboard could be not sending the right signal to the psu about powering the backlights (the UD, or the BLU_PWM voltages?) and this could be the problem resulting in the strobe and crash?
without verified expected voltages on those pins measured from a working set, or an actually useful service manual, whats a tech to do but keep bungling around making semi educated guesses?
i rushed in before taking notes. should have done sound test, mb test, other tests...
or if i did i should have wrote them down but i didnt.
i went straight to the backlights because with the LED tester i was able to see
right away that one of the two strings was open. (wouldn't light up)
there are only 4 wires going to the backlights. 2 black and 2 blue. blue is positive. black is negative. 2 strings, and ones not working.
thinking it would be a straightforward backlight repair (and nothing else wrong!), i opened the panel and
got to work. i found that all the LED's were actually lighting up fine except for one strip. but on that strip when i tested them individually they were all fine.
this puzzled me but eventually i noticed that there was a burnt trace leaving
one of the LEDs unconnected, thus making the whole strip open.
i repaired the trace with some wire, and now both sides (blue and black pairs) responded well to the
LED tester.
both of them using about 115v and lighting up nicely.
i jumped the gun again, and completely reassembled the TV when i should have left it apart to test the psu and backlight combo but i didnt.
once i got it back together and tested the psu and backlight by themselves, or with the mainboard connected i
was now getting a strobing backlight, and im pretty sure its crashing the
mainboard as well because when its connected i cant see any image at all when powering on.
when i leave the backlights diconnected, and all other boards connected normally and power the backlights seperately with the LED tester, i can see the picture is fine, the menu is fine. the LCD is fine, not cracked. the TV looks great, if only a little dark because only one string is being lit.
in this state, i unhooked the led tester from the backlights and plugged the
backlight connector into the PSU and immediately get the strobing light, and
the image that was on the screen gets corrupted in some weird way. and the tv would not respond to power off requests. i had to unplug it.
so what is going on here?
do i still have some kind of problem with my backlights even tho the tester
lights them up fine? i know budm told me the tester doesnt put out as much current as the
psu would, and some LEDS can light fine with the tester but fail under full
current...but how can i test for that? there must be something i can do besides opening this panel again!
voltages to the mb look fine to me
but then again i dont know everything about this board, and there arent any threads about it.
voltages, with MB and BL disconnected:
for the mb connector:
on the 13v pins im getting 12.65
others:
UD: 2.28v (no idea what UD is)
PWM_BLU: 3.24v (seems normal but i just dont know anymore)
PS_ON: 3.24v (ditto)
for the LED connector
im getting 401v on pin 1 and 2 and 0v on all others
(no idea how to know what to expect as normal V+ on these pins with no boards or LED connected, but 400v seems like enough?)
voltages with MB disconnected, BL connected: (while BL strobes, which i dont like to do for very long...is this damaging?)
on all the 13v pins im getting around 5v
and 0 on all the others except 1.6v on the PS_ON pin
on the LED connectors i get 113v on pins 1 and 2, and 0 on all the others.
the 113v seems in line with the 115v i was getting on the readout of the LED tester, but why does it fail?
i actually bought a replacement PSU because it was cheap (25$) and it has all the same voltages and does exactly the same thing as the original, except that when its by itself, the voltage one pin1 and 2 of the LED connector reads 420v instead of 401v
continuity between harness pins and connector pins for LED connector are good. pins are making contact with the wires.
kinda stumped here. really dont want to open the panel again
psu model:
L60H1_EHS BN44-00775A
BN4400775A
what is interesting to note here, is that the mainboard seems to be totally fine with having no backlights connected to the PSU, and if you can light the backlights some other way then you will have a nice tv, though i'd imagine the menu would no longer be able to control the backlight levels...
another thought (creepy) is that the mainboard could be not sending the right signal to the psu about powering the backlights (the UD, or the BLU_PWM voltages?) and this could be the problem resulting in the strobe and crash?
without verified expected voltages on those pins measured from a working set, or an actually useful service manual, whats a tech to do but keep bungling around making semi educated guesses?
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