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This lesson talks about the maintenance of weak WiFi signal

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The performance of weak WiFi signal is that WiFi can be turned on but cannot be connected,

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and the signal is only one grid

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It is usually caused by the failure of the high-frequency transceiver line channel of WiFi,

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Next, look at the WiFi transceiver channel

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Take Huawei's mobile phone as an example

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This is the transceiver channel of the 5G frequency band

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This is the antenna, identified as ANT6

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The signal received by the antenna passes through the normally closed contact and passes through the filter

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After passing through the filter, it passes through the filter again,

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and finally reaches the receiving amplifier chip

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Then form a high-frequency receiving signal and send it to the WiFi chip for processing

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Its transmitting signal goes out from the A14 pin and is sent to the receiving amplifier chip

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The switch inside the receiving amplifier chip is turned on,

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the signal goes out from the second pin to the filter, and finally reaches the antenna

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This is the channel it receives and transmits

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The main components in these channels are normally closed contacts, filters,

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receiving amplifier chips, and WiFi chips

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In the maintenance, it should be noted that the normally closed contact is not corroded by water,

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so it can be ignored

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There is no water corrosion in the filter, no false welding, and there is no need to consider it

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Generally, we only consider receiving amplifier chips

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The receiving amplifier chip has power supply, open signal and bus

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Some are controlled by the bus, some are controlled by the opening signal,

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and there are one or two power supply channels

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Mostly it is a problem with the receiving amplifier chip,

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or a problem with the WiFi chip that causes the signal to be weak

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Next, let's look at the repair method

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The first step is to check the WiFi chip and the front-end chip

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The front-end chip refers to the receive and transmit amplifiers

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Then consider whether the filter is corroded

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No matter which of these components is corroded, the solution is to re-solder

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Test again after re-soldering, if the WiFi signal becomes normal,

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it means that the fault has been repaired

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If the WiFi signal is still weak, we usually replace the components

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In the second step, check these small components in the 2G and 5G channels,

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including resistors, capacitors, inductors

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See if they are severely corroded, causing high-frequency signals to not pass through

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It should be noted that, for example, when the antenna signal comes,

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it reaches the normally closed contact channel through the resistor,

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then passes through the resistor, reaches the filter,

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and then reaches the receiving amplification, and finally gives it to the WiFi chip

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Resistors, capacitors, coaxial switches and filters,

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they do not pass strong currents, only weak currents

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Therefore, they have not been corroded by water and have not been touched by people, so they are not considered

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Another situation is that the positions of these components have no traces of falling,

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and they are not considered

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Direct replace the component with water ingress corrosion

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One end of the component is grounded and the other end is connected to the line

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This kind of component cannot be short-circuited

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Here is a look at these components, what kind of components cannot be short-circuited,

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and what kind of components can be short-circuited

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Let's take Xiaomi 10Pro as an example, open its schematic diagram and bitmap

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Find the WiFi chip U2400

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Find its sending and receiving lines, such as 2 g channel,

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let's look outside

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In the radio frequency circuit of WiFi, both ends of this coupling capacitor are not grounded,

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and this component can be short-circuited

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Continue to look at its signal channel

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Like this component, one end is connected to the signal and the other end is grounded

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This inductance cannot be short-circuited

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Once you short it, you connect the signal directly to ground

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Such a capacitor with one end grounded and one end connected to the signal line cannot be short-circuited

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The inductance in the signal channel can be shorted

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This is a repair for weak WiFi signal

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That's all for this lesson