• Learning center

96. Search for switch pin and standby power supply
In this lesson, we mainly explain how to find the switch pin, how to find the standby power supply.
Detail
Comments

1

00:00:00,300 --> 00:00:04,033

In this lesson, let's learn the maintenance steps of no touch faults

2

00:00:07,000 --> 00:00:10,400

When the ground value of the power supply is measured to be normal,

3

00:00:11,933 --> 00:00:15,466

it is necessary to measure the next working condition of the touch,

4

00:00:15,500 --> 00:00:18,666

that is, the ground value of the reset signal

5

00:00:19,300 --> 00:00:23,066

If there is infinity in the ground value, how should we analyze it?

6

00:00:24,100 --> 00:00:26,233

Take Xiaomi 11 as an example

7

00:00:26,433 --> 00:00:28,100

Open the schematic diagram

8

00:00:28,566 --> 00:00:30,800

TS is touch, RESET is reset

9

00:00:33,100 --> 00:00:34,733

This line is touch reset

10

00:00:36,466 --> 00:00:39,433

It goes to the pin 45 of the touch connector

11

00:00:41,733 --> 00:00:43,233

We switch to bitmap

12

00:00:45,300 --> 00:00:51,033

Double-click the left mouse utton to select the position number J6503 of the touch connector

13

00:00:51,300 --> 00:00:56,033

Right-click and click find the bitmap component, so you can find the touch connector

14

00:01:00,366 --> 00:01:04,433

This is the bitmap, the connector on the actual mainboard is here

15

00:01:06,600 --> 00:01:11,766

Pin 45 is the touch reset signal, let's take a look at its circuit

16

00:01:17,066 --> 00:01:20,400

There is a capacitor connected to this line, let's ignore it

17

00:01:21,366 --> 00:01:22,800

we continue to search

18

00:01:24,233 --> 00:01:31,400

There is a pull-up resistor here, which is powered by VREG_L2C_1P8 to provide pull-up

19

00:01:33,000 --> 00:01:34,300

we continue to search

20

00:01:35,566 --> 00:01:39,433

It goes to pin C28 of CPU U3100

21

00:01:45,433 --> 00:01:50,900

By learning the diagram, we know that there is a capacitor, a pull-up resistor, a CPU,

22

00:01:50,966 --> 00:01:54,133

and a connector J6503 on this line,

23

00:01:54,566 --> 00:01:56,200

a total of four components

24

00:01:56,500 --> 00:02:01,266

During maintenance, when the reset signal of pin 45 is detected as OL,

25

00:02:02,700 --> 00:02:05,800

we first check whether the connector has been soldered

26

00:02:09,200 --> 00:02:12,600

If the connector has been soldered falsely, just re-solder it,

27

00:02:13,466 --> 00:02:16,333

it will return to normal, and the fault can be repaired

28

00:02:16,900 --> 00:02:21,733

If the connector has not been soldered falsely, we measured its ground value is OL

29

00:02:22,200 --> 00:02:27,733

Because this line only connects to the pins of the CPU, it is difficult to handle at this time

30

00:02:29,766 --> 00:02:32,033

Remove the CPU, re-solder it

31

00:02:35,733 --> 00:02:38,200

After soldering, if it is still infinity,

32

00:02:38,766 --> 00:02:42,000

either the CPU is damaged, or the board is broken

33

00:02:45,500 --> 00:02:47,400

CPU damage is irreparable

34

00:02:48,966 --> 00:02:52,366

If the CPU is not damaged, remove the CPU

35

00:02:52,966 --> 00:02:57,533

One marker of the multimeter is placed at the corresponding point on the CPU,

36

00:02:59,933 --> 00:03:05,433

and one marker is placed at pin 45 to measure the continuity of the circuit.

37

00:03:07,533 --> 00:03:11,266

If the line is connected, it proves that the CPU is broken

38

00:03:12,233 --> 00:03:17,966

If it is OL between these two points, we can use the method of flying wire to solve the fault

39

00:03:20,433 --> 00:03:24,166

These are the repair steps when the reset signal value is infinite

40

00:03:25,633 --> 00:03:27,233

That's all for this lesson

No comments yet
Come and write your comments
Links: