Sony Bravia KDL-40v4100 has no picture but has power, backlight, and sound
Hello! I would like to repair my father's Sony Bravia KDL-40v4100 LCD TV. It was in perfect working order the last time I used it before the pandemic. Then it sat plugged in but unused for a year or more. And now everything still works except that there is no picture on the screen. A relay can be heard to click when the power cable is connected. When the power button is pressed there is a green power LED and then the backlight turns on. If I connect an HDMI cable and play something with audio I can hear it through the speakers. The remote control buttons are recognized. There is just never anything except black on the screen.
Per suggestions in other threads here, I measured the voltage at the FP1 fuse near the LVDS connector on the TCON board (by touching the black probe of my analog multimeter to the metal chassis and the red probe to either side of the fuse) and it reads about 12V on either side.
Per the Sony TCON troubleshooting document, I tried partially disconnecting the LVDS connector, rocking it side to side, while the TV was on, to see if anything would appear on the screen, which it did for a split second, flickering on and off a few times. Recording the TV with a slow-motion camera while doing this revealed that the picture that briefly appeared was in fact a reasonable image (black and white static over the whole screen overlaid with "PBS" and the PBS logo centered at the top, a channel number at the upper right, and "No signal" at the bottom). I got the same result regardless whether I did this to the LVDS connector at the TCON or the one at the BU board.
I've read that two different models of TCON and panel were used for this TV model. This TCON is labeled FS_HBC2LV2.4. There is also a barcode reading K2275E8B01CZ 001763. I believe this is the board ShopJimmy also refers to as Samsung LJ94-02275E.
The service manual says the standby LED will blink to indicate certain types of detected failures (including some TCON failures) but that's not happening here. The standby LED is off, only the power LED is on.
Do the symptoms I've described suggest any particular troubleshooting steps to perform next? I have not repaired a TV before but I have a little experience with electronics. Photos of the TCON board, power supply board, and BU board are attached. Thanks for any advice.
Per suggestions in other threads here, I measured the voltage at the FP1 fuse near the LVDS connector on the TCON board (by touching the black probe of my analog multimeter to the metal chassis and the red probe to either side of the fuse) and it reads about 12V on either side.
Per the Sony TCON troubleshooting document, I tried partially disconnecting the LVDS connector, rocking it side to side, while the TV was on, to see if anything would appear on the screen, which it did for a split second, flickering on and off a few times. Recording the TV with a slow-motion camera while doing this revealed that the picture that briefly appeared was in fact a reasonable image (black and white static over the whole screen overlaid with "PBS" and the PBS logo centered at the top, a channel number at the upper right, and "No signal" at the bottom). I got the same result regardless whether I did this to the LVDS connector at the TCON or the one at the BU board.
I've read that two different models of TCON and panel were used for this TV model. This TCON is labeled FS_HBC2LV2.4. There is also a barcode reading K2275E8B01CZ 001763. I believe this is the board ShopJimmy also refers to as Samsung LJ94-02275E.
The service manual says the standby LED will blink to indicate certain types of detected failures (including some TCON failures) but that's not happening here. The standby LED is off, only the power LED is on.
Do the symptoms I've described suggest any particular troubleshooting steps to perform next? I have not repaired a TV before but I have a little experience with electronics. Photos of the TCON board, power supply board, and BU board are attached. Thanks for any advice.
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