As we all know, LVDS signals are sent to the logic board through the upper screen line, and then sent to the logic board by a transmitter and a demodulator on the motherboard. The phenomenon that the two circuits have problems is the same, so it is difficult to judge. Because the signals output by LVDS are 5 pairs (SD screen) or 10 pairs (HD screen) differential signals, that is, the same pair of data lines output signals with opposite phases and the same amplitude, and the voltage is about 1- 1.5V, so it can be judged by measuring the waveform with an oscilloscope.

If there is a gray screen phenomenon, first check whether the power supply of the upper screen line is normal (generally, there are 5V and 12V screens, and 3.3V screens are rare), and then measure whether the differential signal is symmetrical with an oscilloscope and whether the differential signal voltage changes when operating the corresponding function menu of the TV. If the voltage is normal, the differential signal is symmetrical and the signal voltage changes, it can be judged that the logic board is defective.

The following are several common LVDS interface definitions

20 needles single 8 definition:

1: power supply 2: power supply 3: grounding 4: grounding 5: r0-6: r0+7: grounding 8: r1-9: r1+10: grounding1.

The resistance between each group of signal lines is about (digital meter 120 ohm).

30 needles single 6 definition:

1: empty 2: power 3: power 4: empty 5: empty 6: empty 7: empty 8: r0-9: r0+ 10: ground1:r1-1. 17: clk-18: clk+19: ground 20: empty -2 1: empty 22: empty 23: empty 24: empty 25: empty 26: empty 27: empty 28, empty 29, empty 29.

The resistance between each group of signal lines is about (digital meter 120 ohm).

30 needles single 8 definition:

1: empty 2: power 3: power 4: empty 5: empty 6: empty 7: empty 8: r0-9: r0+ 10: ground1:r1-1. 17: clk-18: clk+19: ground 20: R3-2 1: R3+22: ground 23: empty 24: empty 25: empty 26: empty 27: empty 28, empty 29.

The resistance between each group of signal lines is about (digital meter 120 ohm).

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: ground1. k+ 16:Di 17:RS0- 18:RS0+ 19:Di 20:RS 1-2 1:RS 1+22:Di 23:RS2。

The resistance between each group of signal lines is about (digital meter 120 ohm).

30-pin 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-kloc-0/:r1. CLK+ 17: Di18: R3-19: R3+20: RBO-21:RBO+22: RBO1-23: RBO/kloc-0.

The resistance between each group of signal lines is about (digital meter 120 ohm).

Generally, 14PIN, 20PIN and 30PIN are LVDS interfaces.