1

00:00:00,100 --> 00:00:03,800

We talk about how to repair the fault of no display in this lesson

2

00:00:04,000 --> 00:00:05,766

Let's look at the reset signal

3

00:00:06,266 --> 00:00:11,833

In fact, the reset judgment method and the detection judgment method are exactly the same

4

00:00:12,500 --> 00:00:14,133

The reset pin is here,

5

00:00:14,666 --> 00:00:18,900

What if there is an infinity or a short circuit when we measure the reset?

6

00:00:19,600 --> 00:00:24,333

LCT_RESET_N is the reset signal of the display

7

00:00:25,666 --> 00:00:27,333

Let's take a look at its line

8

00:00:27,733 --> 00:00:30,366

There is a CR6400 outside

9

00:00:30,933 --> 00:00:34,933

This CR6400 is an anti-static protection diode

10

00:00:35,433 --> 00:00:38,000

If it is corroded by water and damaged,

11

00:00:38,366 --> 00:00:41,900

it will cause us to measure this point as a short circuit to ground

12

00:00:45,633 --> 00:00:49,466

We must first remove this component CR6400

13

00:00:53,666 --> 00:00:59,333

because it is connected to the ground wire GND at one end, the gray end

14

00:01:00,666 --> 00:01:03,133

This end is connected to the reset line

15

00:01:04,566 --> 00:01:06,833

So what would it cause if it was damaged?

16

00:01:07,366 --> 00:01:10,400

lead to leakage, resulting in a short circuit,

17

00:01:10,566 --> 00:01:12,633

at this time, we can remove it

18

00:01:13,033 --> 00:01:17,300

We take down this CR6400 and face two situations

19

00:01:18,800 --> 00:01:23,200

First, the reset signal of pin 22 is not short-circuited,

20

00:01:23,566 --> 00:01:27,466

basically we have repaired it, and the screen can display

21

00:01:30,700 --> 00:01:35,366

Second, the reset signal of pin 22 is still short-circuited

22

00:01:35,633 --> 00:01:38,933

At this time, if the CPU has not been repaired,

23

00:01:39,233 --> 00:01:41,466

and there is no tin explosion around,

24

00:01:42,500 --> 00:01:48,233

there is basically no repair value, and we can just return the machine to the customer

25

00:01:53,433 --> 00:01:56,466

Because this CPU is more likely to be damaged

26

00:01:56,966 --> 00:02:02,366

We can also remove the CPU and re-solder it, no longer short circuit,

27

00:02:05,166 --> 00:02:10,166

that is, the fault is repaired, but this situation is very rare,

28

00:02:12,066 --> 00:02:15,366

because if there is no tin explosion around the CPU,

29

00:02:15,633 --> 00:02:19,266

you can't re-solder the CPU and it will be fine

30

00:02:28,500 --> 00:02:32,533

This is a short circuit, and there is another case of infinity

31

00:02:33,466 --> 00:02:36,333

If the reset signal is measured to be infinite,

32

00:02:37,033 --> 00:02:40,333

we don't need to care about the CR6400,

33

00:02:40,633 --> 00:02:44,100

because the reset signal is directly connected to the CPU

34

00:02:44,566 --> 00:02:48,766

The ground value we measure is the ground value it leads to the CPU

35

00:02:53,966 --> 00:02:55,733

When we measure this infinity,

36

00:02:55,966 --> 00:02:58,400

we remove the CPU and re-solder

37

00:03:05,400 --> 00:03:08,266

Two scenarios for re-soldering a CPU

38

00:03:09,733 --> 00:03:12,666

The first case is that the value is restored,

39

00:03:13,233 --> 00:03:17,200

which means that the fault has been repaired and the screen can be displayed

40

00:03:23,200 --> 00:03:28,466

The second case is that the value is still infinite, which is not very easy to fix

41

00:03:29,066 --> 00:03:32,000

Either a board layer problem or a CPU problem

42

00:03:32,366 --> 00:03:36,966

Remove the CPU, find the corresponding reset point on the CPU,

43

00:03:37,833 --> 00:03:40,666

and test whether the CPU itself is infinite

44

00:03:40,900 --> 00:03:43,033

If there is an infinity on the CPU,

45

00:03:43,166 --> 00:03:46,400

it can't be fixed, just return it to the customer

46

00:03:49,666 --> 00:03:52,866

As for whether the fault on the CPU can be repaired,

47

00:03:53,066 --> 00:03:55,900

and whether the problem of the board can be repaired,

48

00:03:56,266 --> 00:03:58,000

we will talk about it later

49

00:03:58,566 --> 00:04:02,100

Well, this is a problem with the reset, how do we judge

50

00:04:03,300 --> 00:04:05,333

Okay, that's it for this lesson