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This lesson talks about the maintenance for no baseband fault of mobile phones with independent baseband

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After performing the above two steps and re-soldering the baseband, the power-on test still has no baseband

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The maintenance method is to first measure the ground value of the main power supply of the baseband to see if it is low or short-circuited

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If it is a short circuit, check the capacitor or chip connected to the line

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Generally, the capacitance is considered, and then the chip is considered

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If there is no short circuit to the ground value,

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remove the baseband CPU and measure the solder joint of the chip where the baseband CPU leads to

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Usually measure the ground value to determine

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whether there is an open circuit or a short circuit in the signal channel

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If there is a short circuit in the signal leading to other chips,

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generally remove the capacitor connected to the line first

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If there is still a short circuit, then measure the chip

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Among these chips, the radio frequency chip, baseband power supply or clock chip can be replaced,

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but the large CPU cannot be replaced

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If OL appears in the measured ground value, check whether there is a capacitor connected in the line

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Because in the line where the capacitors are connected in series,

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it is normal to measure the value of infinity to the ground, this should be paid attention to

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If there is no capacitor in the line, first resolder the chip in the line

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After re-welding, if the ground value returns to normal, it means that the fault has been repaired

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If the ground value is still infinite after re-soldering, you need to replace the chip in the circuit

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The baseband power supply chip and the clock chip can be replaced,

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but the large CPU cannot be replaced and can only be re-soldered

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This is the maintenance for no baseband fault of mobile phones with independent baseband

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That's all for this lesson