There is no response when the USB flash drive is inserted into the machine. Maintenance idea: According to the fault phenomenon, the entire USB flash drive is not working, and the conditions required for the USB flash drive are the focus of our maintenance. Regardless of any scheme, the USB flash drive must have the following conditions to work: (1) Power supply is divided into the power supply required by the main control and the power supply required by the FLASH. These two are the key, and the circuit of the USB flash drive is very simple. If there is no power supply, it is generally the insurance inductor is damaged or the 3.3V voltage regulator block is damaged. When it comes to the voltage regulator block, I will also talk about it here. Its three pins are power input (5V), ground, and power output (3.3).
1. There is no response when the USB flash drive is inserted into the machine. Maintenance ideas: According to the fault phenomenon, the entire USB flash drive is not working, and the requirements for the USB flash drive tools are the focus of our maintenance. No matter what the U disk of any scheme wants to work, it must have the following conditions:
(1) The power supply is divided into the power supply required by the main control and the power supply required by the FLASH. These two are the key. The U disk circuit is very simple. If there is no power supply, the insurance inductor is usually damaged or the 3.3V voltage regulator block is damaged. , Speaking of the voltage regulator block, let’s also talk about it here. Its three pins are power input (5V), ground, and power output (3.3). The working principle is that when a 5V voltage is input to the input pin, the output pin will output. A stable 3.3V. As long as the source of the lack of power is found, the problem will be solved.
(2) Clock, because the main control can only work at a certain frequency, and the communication with FLASH also depends on the clock signal for transmission, so if the clock signal is not available, the main control will definitely not work. When checking this circuit, the clock generation circuit is actually very simple. You only need to check the crystal oscillator and its peripheral circuits. Because the crystal oscillator is afraid of brushing and the U disk is small and it is easy to fall on the ground and cause damage to the crystal oscillator, just replace the same crystal oscillator. can. Note: The crystal oscillator cannot be measured. The best way to judge its quality is to replace it with a good one. (3) The main control, if the above two conditions are normal, then the main control chip is damaged.
2. Insert the U disk into the computer, and prompt “unrecognized device”.
Maintenance idea: Regarding this phenomenon, the first point shows that the circuit of the U disk is basically normal, but there is only a malfunction in the communication with the computer, and the following points should be checked for the communication:
(1) U disk interface circuit. There is no special component in this circuit, that is, two data lines D+ D-, so when checking this circuit, you only need to measure whether the line between the data line and the main control is normal, usually in the data line. There will be two small resistance resistors connected in series with the main control circuit to play a protective role, so it is necessary to check whether the resistance of these two resistors is normal.
(2) Clock circuit, because the USB flash drive communicates with the computer at a certain frequency, if the operating frequency of the USB flash drive cannot be synchronized with the computer, the system will consider it an “unrecognized device”. The crystal oscillator must be changed at this time. In actual repairs, there are really many examples of crystal damage!
(3) The main control, if the above two checks are normal, then it can be judged that the main control is damaged.
3. U disk can be recognized, but when it opens, it prompts “The disk has not been formatted” but the system cannot format it.
or prompt “Please insert the disk”, open the U disk, there are garbled characters, the capacity does not match with itself, etc. Maintenance idea: For this phenomenon, it can be judged that the hardware of the U disk itself is not too problematic, it is just a software problem. Solution: Find the repair tool of the master control program and do it. This is up to everyone to see what the main control scheme of the U disk is to decide. Re-production of U disk is the last and most effective way to solve the problem. You can use chipgenius to detect the model of the chip, then download the mass production tool for the corresponding chip, and mass produce the U disk.
U disk failure is probably these main problems. As for the inability to write files, non-storage, etc., it is generally caused by poor FLASH performance or bad blocks.
