Hi all,
I'm new to this forum so sorry if I missed any important info. Have read the rules and all. So---
Recently I found this 42" LG TV in a trash yard, it looked nice and most importantly the screen was not cracked so I took it home. Upon connecting the TV to mains, it turned on, the Standby LED blinked 2 times (I read this is normal as the TV boots up) and I managed to tune in local TV stations over DVB-T. The sound works, but the LCD panel doesn't. It's continuously black from the start-up. The backlight glows and occassionally changes its brightness depending on the displayed scene.
Judging by this behavior, I assumed it is the T-Con board fault. So I ordered a new one from Aliexpress.
T-con P/N: 6870C-0401B
MODEL: 32/37/42/47/55 FHD TM120 Ver 0.2
After a month of waiting, the module shipped in, and I replaced it only to find out the LCD is still dark.
I tried to disconnect one of the ribbon cables leading from T-con to the Buffer board of the LCD (there are two buffer boards, the panel is split to two sections). I expected one half of the panel to go blank and pass the white backlight. But it stayed black. So I tried to disconnect both sections of the panel, still the panel was all dark, not letting any light through. I wanted to check if there's something wrong with the control chips located on the sides of the panel, but I found none, so I guess those are already somehow integrated in the ones located along the bottom of the panel.
Then I measured the T-Con supply voltage, and measured 12V just fine. I also checked the continuity of all the wires in the LVDS cable and they all seem fine.
After finding no issues with supply voltages there, I moved onto the Main board.
Main board model: LD21B/LC21B
EAX64317404(1.0) G4_L_TU123
Measured some of the test points located near the LVDS connector, I found 12V.
Then I measured all the pins of the Power connector on the main board.
Results are:
That one pin which reads fluctuating voltage 0.8 to 3.4V was usually stepping between 2.4 and 3.4V, very precisely, so I'd say that is an intended function. The 0.8V might've been just a measurement error.
The rest of the photos for this TV is available in this Imgur album http://imgur.com/a/eXNoN
I'll also attach the Service manual for this TV.
Full name of this particular model is the 42LM615S-ZE
----
I wish I had an oscilloscope to measure the output LVDS signals (if the CPU even outputs anything at all), but all I got is a cheap multimeter so I'm very limited in terms of debug equipment.
Thank you for help.
I'm new to this forum so sorry if I missed any important info. Have read the rules and all. So---
Recently I found this 42" LG TV in a trash yard, it looked nice and most importantly the screen was not cracked so I took it home. Upon connecting the TV to mains, it turned on, the Standby LED blinked 2 times (I read this is normal as the TV boots up) and I managed to tune in local TV stations over DVB-T. The sound works, but the LCD panel doesn't. It's continuously black from the start-up. The backlight glows and occassionally changes its brightness depending on the displayed scene.
Judging by this behavior, I assumed it is the T-Con board fault. So I ordered a new one from Aliexpress.
T-con P/N: 6870C-0401B
MODEL: 32/37/42/47/55 FHD TM120 Ver 0.2
After a month of waiting, the module shipped in, and I replaced it only to find out the LCD is still dark.
I tried to disconnect one of the ribbon cables leading from T-con to the Buffer board of the LCD (there are two buffer boards, the panel is split to two sections). I expected one half of the panel to go blank and pass the white backlight. But it stayed black. So I tried to disconnect both sections of the panel, still the panel was all dark, not letting any light through. I wanted to check if there's something wrong with the control chips located on the sides of the panel, but I found none, so I guess those are already somehow integrated in the ones located along the bottom of the panel.
Then I measured the T-Con supply voltage, and measured 12V just fine. I also checked the continuity of all the wires in the LVDS cable and they all seem fine.
After finding no issues with supply voltages there, I moved onto the Main board.
Main board model: LD21B/LC21B
EAX64317404(1.0) G4_L_TU123
Measured some of the test points located near the LVDS connector, I found 12V.
Then I measured all the pins of the Power connector on the main board.
Results are:
That one pin which reads fluctuating voltage 0.8 to 3.4V was usually stepping between 2.4 and 3.4V, very precisely, so I'd say that is an intended function. The 0.8V might've been just a measurement error.
The rest of the photos for this TV is available in this Imgur album http://imgur.com/a/eXNoN
I'll also attach the Service manual for this TV.
Full name of this particular model is the 42LM615S-ZE
----
I wish I had an oscilloscope to measure the output LVDS signals (if the CPU even outputs anything at all), but all I got is a cheap multimeter so I'm very limited in terms of debug equipment.
Thank you for help.
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