Wonder why the LED TV screen flicking like crazy and look washed out in white noise? Particularly when you enter the service mode for the first time?
With a wrong v-com value, the TV screen will look washed out with continue flickering.
When the vcom value was wrong, you cannot even see the service menu text clearly. The screen just flick like crazy. When you getting close to the correct value of the vcom, the text on the service menu will became clearer and clearer with a relatively steady background.
In one case, a vcom value around 0x60 gives better result.
The following is quoted from the TC-L42U30-SM.pdf service manual chapter 8.
When replacing LCD panel, TC board (T-CON) or both, [VCOM] Adjustment have to be done. Data for VCOM Adjustment is different depend on the LCD panel and the data is stored in TC board.
Adjustment procedures are as follows.
When replacing LCD panel, TC board or both, [VCOM] Adjustment have to be done.
- Set to Service mode
While pressing [ VOLUME ( - ) ] button of the main unit, press [ INFO ] button of the remote control three times within 2 seconds.
- Go into VCOM value indication
Go into main item ADJUST by pressing [1] button on remote control. Go into sub item VCOM by pressing [3] button on remote control. Adjustment value of VCOM is displayed.
- Flicker Confirmation
Go to flicker adjustment screen by pressing [5] button on remote control. Confirm if flicker can be seen.
No flicker --- Exit from Service mode.
Flicker --- Adjustment have to be done.
- VCOM Adjustment (Flicker Adjustment)
This procedure writes into EEPROM correct data so the panel does not flicker. Press remote control [+/ -] button to delete or minimize the flicker in flicker adjustment screen. Press [ OK ] button. Correct data is automatically written into EEPROM (IC9206).
Caution: The data can be written into EEPROM only 15 times. Don’t press [ OK ] button many time. If the data can not be written, replace TC board or IC9206 to new one.
- Exit from Service mode
Switch off the power with the [ POWER ] button on the main unit or the [ POWER ] button on the remote control
To get into service mode:
- Hold [Vol -] button on the TV set and press [Info] key on the remote 3 times quickly.
- remote [1] [2] to navigate the main menu
- remote [3] [4] to navigate the submenu
- other number keys on the remote have special meaning depends on the menu.
- remote [OK] button to save result.
In the step 4, use remote [VOL +/-] keys to change the vcom value, NOT in the flickering test mode under [5] button.