I came across a 50inch TU8000 that wouldnt start up properly (blinking stand-by light, backlights would cycle on and off).
When i opened it up and removed the power to the mainboard the backlights powered up and everything looked uniform.
When reconnected the mainboard but disconnected the flex cable to the panel i heard the TV startup with the intro sound.
Later I checked for shorts on the panel PCB boards but could not find anything.
When I took a look with the FLIR i noticed the 2 resistors (2701 at R43 and R44) where really hot even though the panel was not working.
I measured their resistance and they were about 5% lower than what they should have been (around 2400-2500 ohms). I didnt think this was too egregious but for good measure I was prepared to replace them as I didnt know if that was enough to cause the TV not to startup.
Before I did set out to change them out I disconnected the flex cable from the mainboard and measured again.
I was surprised to find that the resistance had gone back up to within +/-1% spec.
Can anyone explain the two phenoms to for me?
1) Why the resistors were running hot even though the TV was not displaying an image (yes there is a short somewhere on the panel but Im expecting the mainboard to cut power to the panel or something).
2) Why the resistance of the two resistors dropped when the flex cable was connected to the mainboard.
I was able to isolate and mask off the one trace that was causing the bootloop but i was never able to get any picture even after several rounds of carefully masking off other traces.
I gave up on the panel but questions still linger on my mind about the facts of the case.
Thanks in advance
When i opened it up and removed the power to the mainboard the backlights powered up and everything looked uniform.
When reconnected the mainboard but disconnected the flex cable to the panel i heard the TV startup with the intro sound.
Later I checked for shorts on the panel PCB boards but could not find anything.
When I took a look with the FLIR i noticed the 2 resistors (2701 at R43 and R44) where really hot even though the panel was not working.
I measured their resistance and they were about 5% lower than what they should have been (around 2400-2500 ohms). I didnt think this was too egregious but for good measure I was prepared to replace them as I didnt know if that was enough to cause the TV not to startup.
Before I did set out to change them out I disconnected the flex cable from the mainboard and measured again.
I was surprised to find that the resistance had gone back up to within +/-1% spec.
Can anyone explain the two phenoms to for me?
1) Why the resistors were running hot even though the TV was not displaying an image (yes there is a short somewhere on the panel but Im expecting the mainboard to cut power to the panel or something).
2) Why the resistance of the two resistors dropped when the flex cable was connected to the mainboard.
I was able to isolate and mask off the one trace that was causing the bootloop but i was never able to get any picture even after several rounds of carefully masking off other traces.
I gave up on the panel but questions still linger on my mind about the facts of the case.
Thanks in advance
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