When the TV cold starts, it works mostly fine. I have noted that all backlights are uniformly dimmer towards the middle of the screen. As the TV remains on, the dimmer spot progressively goes away. Right about the same time the backlights are uniformly on throughout, they shut off, about 3 min after cold start. Sound works, picture is there with flashlight test. If I turn the TV off and back on again, backlights stays on for only few seconds and then I am back to sound only, and picture with flashlight only.
At first glance all internal parts and components look OK. At all times I am getting psu on and backlight on signal from main board, even after backlights shut off. Even though it was a long shot, I have visually inspected the CCFLs themselves, and they all look OK, no burned spots or overly darkened area near connectors. I have noticed that right before the backlights go out, they start pulsing about 4 times per second as if someone is adjusting the backlight intensity in menu.
I believe that the problem lies with PSU. If I bypass the main board, I still get same issues with backlights. When the backlights go off and I unplug the cable between PSU and inverter, wait few seconds, and plug it back in they do not come on. If however I unplug the PSU from the wall, wait few seconds, and plug it back in they come on only for few seconds. Backlights are on for few minutes only if TV sits for some time before I turn it back on again.
Capacitors on the PSU look OK. In my research I came across someone mentioning that the Polyfilm caps like to go bad. I have removed mine form the circuit, and they all read withing less than 10% of their value. The two main filter caps also read OK at all times.
I am not sure what to look at next at this point.
Thanks for your input
PSU: BN44-00441A
Inv: 27-D056702
Main: Part number sticker is missing, but they seem to be cross compatible with each other
At first glance all internal parts and components look OK. At all times I am getting psu on and backlight on signal from main board, even after backlights shut off. Even though it was a long shot, I have visually inspected the CCFLs themselves, and they all look OK, no burned spots or overly darkened area near connectors. I have noticed that right before the backlights go out, they start pulsing about 4 times per second as if someone is adjusting the backlight intensity in menu.
I believe that the problem lies with PSU. If I bypass the main board, I still get same issues with backlights. When the backlights go off and I unplug the cable between PSU and inverter, wait few seconds, and plug it back in they do not come on. If however I unplug the PSU from the wall, wait few seconds, and plug it back in they come on only for few seconds. Backlights are on for few minutes only if TV sits for some time before I turn it back on again.
Capacitors on the PSU look OK. In my research I came across someone mentioning that the Polyfilm caps like to go bad. I have removed mine form the circuit, and they all read withing less than 10% of their value. The two main filter caps also read OK at all times.
I am not sure what to look at next at this point.
Thanks for your input
PSU: BN44-00441A
Inv: 27-D056702
Main: Part number sticker is missing, but they seem to be cross compatible with each other
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