Application of DC Stabilized Power Supply in Mobile Phone Maintenance
1-current method
In mobile phone maintenance, there are many maintenance methods, and for secondary vocational students =. For the first grade students, they have been able to master the use of the multimeter proficiently, so students can also use the current method to judge the scope of mobile phone failures with the help of maintenance power supply. The current method is a commonly used method in mobile phone maintenance. It is most widely used when repairing the failure of the mobile phone to turn on. current, search current, transmit current, and standby current"
(1) Start-up current. The battery current refers to the current when the power button of the mobile phone is pressed after the power is turned on. The normal battery current is generally 0-120n, but it should also be noted that the normal battery current of different types of mobile phones will be different.
(2) Search net current. The network search current refers to the changing current when the mobile phone is turned on and enters the network search. The normal network search current is generally about 100u, and then falls back to 7 or 10mA, indicating that the mobile phone has searched the network.
(3) Emission current. The emission current refers to the changing current of the mobile phone when it is in the call state, generally around 35).
(4) Standby current. The standby current refers to the current of about 20" when the mobile phone searches the Internet, all the background programs of the mobile phone are closed, and the screen is not bright. If it is too large, it means that the mobile phone is seriously charged and the battery is not durable.
2. Use DC power supply to judge the fault range of the mobile phone not turning on
(1) The mobile phone has a large current when it is powered on, generally greater than 200mA, and the maximum can reach about 1000mA. Focus on checking the relevant B+ circuits in the mobile phone circuit, such as the large filter capacitor of the power supply, power IC, switch control tube, logic power supply tube, radio frequency power supply tube, power amplifier, vibrator and other circuits; check whether there is a short circuit, whether the rear case is short circuited,
(2) There is a small leakage phenomenon when the mobile phone is powered on, generally lower than 50n
Generally, it is caused by insufficient trigger voltage of the machine. Focus on checking the power button and the small components on the power trigger circuit. To reduce the risk, you can clean and deal with them one by one.
(3) Press the power button and the pointer of the ammeter does not move. It is generally regarded as OmA. Generally, it means that the power button is disconnected or the power cable is broken. weld.
(4) Press the power button and the ammeter hardly moves, between 0 and 15n. This kind of current is divided into two types. One is that it flickers between 0 and 0.00, which is generally caused by the poor contact of the 13MH two crystal itself or crystal denaturation, which cannot generate an oscillation frequency; the other is that it stays at 0-15 mA for 3-5 minutes Back to zero, one is a disconnection problem at the receiving side of the 13N circuit, such as a disconnection at the intermediate frequency circuit, the 13MH2 receiving circuit, etc.
(5) Press the power button and the ammeter indicates 20, 30mA to stand still. Indicates that the power supply has started to work, but the CPU has not started, and the general problem occurs in
On the power supply line of the CPU, it is more common for a certain line to be disconnected.
(6) Press the power button, the ammeter rises to 30mA, suddenly jumps to 50-7, and then quickly returns to zero, indicating that the U is damaged, which is a typical failure.
(7) Press the button and the ammeter rises to 40, 60n and keeps "jittering 0", indicating that after the power supply starts to work, the CPU has started to partially start. There is trouble in reading the data of the computer, and the CPU does not know whether to Continue to shutdown or perform shutdown, so it "shakes", up and down, this is a typical software problem, which can be repaired by rewriting the software.
(8) Press the power button and the ammeter rises to 40-60n and then returns to zero "indicating that there is a fault in the logic circuit, generally because the CPU, temporary memory, and word are welded or damaged. In most cases, it must be replaced first, and then judged point of failure.
