How to accurately and quickly determine the LCD TV LVDS interface failure - android - Phones Developers

MOS power IC full range

Photocoupler

In the maintenance, you will encounter some gray screen machines (the "gray screen" here means that there is sound, the operation function is normal, the backlight is also bright, not white screen, no image, no characters, you can see the light from the side of the screen. Light), the main reason for this kind of machine is that the motherboard LVDS or the screen logic board is faulty (power supply is normal), then how to judge whether it is a motherboard problem or a screen logic board problem?
As is known, the LVDS signal has a transmitter on the main board and a demodulator after being sent to the logic board through the upper screen line. The phenomenon in which the two circuits have problems is consistent, which makes it difficult to judge. Because the signal output by LVDS is 5 pairs (standard definition screen) or 10 pairs (high definition screen) differential signals, that is, the same pair of data lines output signals with opposite phase and amplitude, the voltage is about 1-1.5V, so you can pass the oscilloscope. The waveform is measured to make a judgment.
If the gray screen phenomenon, first check whether the power supply of the upper screen line is normal (generally there are 5V and 12V mostly, 3.3V screen is rare), then use the oscilloscope to measure whether the differential signal is symmetrical, and operate the differential signal of the corresponding function menu of the TV. Whether the voltage changes, etc. If the voltage is normal, the differential signal is symmetrical, and the signal voltage changes, it can be determined that the logic board is defective.
Below are several common LVDS interface definitions
20PIN single 8 definition:
1: Power supply 2: Power supply 3: Ground 4: Ground 5: R0-6: R0+ 7: Ground 8: R1- 9: R1+ 10: Ground 11: R2- 12: R2+ 13: Ground 14: CLK- 15: CLK+ 16 :R3- 17:R3+
The resistance between each group of signal lines is (the digital table is about 120 ohms)

30PIN single 6 definition:
1: Empty 2: Power 3: Power 4: Empty 5: Empty 6: Empty 7: Empty 8: R0-9: R0+ 10: Ground 11: R1- 12: R1+ 13: Ground 14: R2- 15: R2+ 16: Ground 17: CLK- 18: CLK + 19: Ground 20: Empty - 21: Empty 22: Empty 23: Empty 24: Empty 25: Empty 26: Empty 27: Empty 28 Empty 29 Empty 30 Empty The resistance between each group of signal lines is (The digital meter is around 120 Euros)

30PIN single 8 definition:
1: Empty 2: Power 3: Power 4: Empty 5: Empty 6: Empty 7: Empty 8: R0-9: R0+ 10: Ground 11: R1- 12: R1+ 13: Ground 14: R2- 15: R2+ 16: Ground 17: CLK- 18: CLK + 19: Ground 20: R3- 21: R3 + 22: Ground 23: Empty 24: Empty 25: Empty 26: Empty 27: Empty 28 Empty 29 Empty 30 Empty The resistance between each group of signal lines is (The digital meter is around 120 Euros)

30PIN double 6 definition: 1: power supply 2: power supply 3: ground 4: ground 5: R0-6: R0 + 7: ground 8: R1 - 9: R1 + 10: ground 11: R2 + 12: R2 + 13: ground 14: CLK - 15: CLK+ 16: Ground 17: RS0- 18: RS0+ 19: Ground 20: RS1- 21: RS1+ 22: Ground 23: RS2- 24: RS2+ 25: Ground 26: CLK2- 27: CLK2+
The resistance between each group of signal lines is (the digital table is about 120 ohms)

30PIN double 8 definition:
1: Power supply 2: Power supply 3: Power supply 4: Empty 5: Empty 6: Empty 7: Ground 8: R0-9: R0+ 10: R1- 11: R1+ 12: R2- 13: R2+ 14: Ground 15: CLK- 16 :CLK+ 17: Ground 18:R3- 19:R3+ 20:RB0-21:RB0+ 22:RB1- 23:RB1+ 24:Last 25:RB2- 26:RB2+ 27:CLK2- 28:CLK2+ 29:RB3- 30:RB3+
The resistance between each group of signal lines is (the digital table is about 120 ohms)
Generally 14PIN, 20PIN, 30PIN are LVDS interfaces.