The owner of this Sharp Aquos LC-52LE810UN said the TV turned worked off and on and won't stay on. However, for me it was completely dead, no light, no nothing. Here's what I've done on the power board:
1. Checked the standby voltage at the output connector: confirmed 5v. This rules out the primary side of the power board.
2. There was no PSU_ON signal from the motherboard/main board
3. There was no AC_DET
4. There was no 12v at the PL (TCON panel) connector
5. There was no UR 13v
6. The main caps showed 160v.
At this point I amateurishly presumed it was the main board. Ordered a used one for $70. No change whatsoever. Started poking around the power board again and decided to jumper PSU_ON and got UR13V. Cool. But still no AC_DET, no PL and the caps are now showing about 60v each.
Next traced the PL 12v back to the input side of the 4 pin voltage regulator. It's getting 13v but not supplying 12v. Saw a post about this that said these regulators often fail. Sweet, removed the regulator (which is on a heat sink with two transistors). Decided to bench test it and it tested fine. I failed to take into account that the fourth pin is the on/off signal and it wasn't supplying the 12v because it was getting the off (0v) signal. sigh. Put the heat sink and the three transistor/regulators back in and ended up lifting a trace. sigh. Fixed that with a jumper wire. Got everything back together and verified it working (as it did before). Then jumped the AC_DET pin and supplied 5v to the 12v PL regulator to force it on. Now I have the logo flashing, yay!. It's blinking 2 slow and 5 fast. That's a bad panel power code.
I don't know where to go at this point as I'm not familiar with LCDs, I know there are inverters that power the backlight. Would that be a fluorescent backlight in this case or LED strings? I do see two small LED connectors at the top right of the power board. I don't know what type of voltage they take but I assume something in the range of 60v each? I think my bench PSU maxes out at 30v.
I found a very similar issue on this thread by @tibimakai but I think in the end he ended up finding a cracked LCD I wonder if mine's the same way as I do see a little oil/water type sheen in some places of the dark LCD https://www.badcaps.net/forum/showthread.php?t=22299
I think I've given up on this as 'cannot be fixed' but part of me says where's the fun in that?
1. Checked the standby voltage at the output connector: confirmed 5v. This rules out the primary side of the power board.
2. There was no PSU_ON signal from the motherboard/main board
3. There was no AC_DET
4. There was no 12v at the PL (TCON panel) connector
5. There was no UR 13v
6. The main caps showed 160v.
At this point I amateurishly presumed it was the main board. Ordered a used one for $70. No change whatsoever. Started poking around the power board again and decided to jumper PSU_ON and got UR13V. Cool. But still no AC_DET, no PL and the caps are now showing about 60v each.
Next traced the PL 12v back to the input side of the 4 pin voltage regulator. It's getting 13v but not supplying 12v. Saw a post about this that said these regulators often fail. Sweet, removed the regulator (which is on a heat sink with two transistors). Decided to bench test it and it tested fine. I failed to take into account that the fourth pin is the on/off signal and it wasn't supplying the 12v because it was getting the off (0v) signal. sigh. Put the heat sink and the three transistor/regulators back in and ended up lifting a trace. sigh. Fixed that with a jumper wire. Got everything back together and verified it working (as it did before). Then jumped the AC_DET pin and supplied 5v to the 12v PL regulator to force it on. Now I have the logo flashing, yay!. It's blinking 2 slow and 5 fast. That's a bad panel power code.
I don't know where to go at this point as I'm not familiar with LCDs, I know there are inverters that power the backlight. Would that be a fluorescent backlight in this case or LED strings? I do see two small LED connectors at the top right of the power board. I don't know what type of voltage they take but I assume something in the range of 60v each? I think my bench PSU maxes out at 30v.
I found a very similar issue on this thread by @tibimakai but I think in the end he ended up finding a cracked LCD I wonder if mine's the same way as I do see a little oil/water type sheen in some places of the dark LCD https://www.badcaps.net/forum/showthread.php?t=22299
I think I've given up on this as 'cannot be fixed' but part of me says where's the fun in that?
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