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

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The first step is to observe whether the main components of the baseband circuit have water corrosion

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The main components observed here are baseband, baseband power supply, and radio frequency chip

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Chip corrosion is generally re-soldered first

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For example, the baseband CPU can only be re-soldered, but not replaced at will

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If the RF chip is corroded by water, if it fails after re-soldering, it must be replaced

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What is often encountered in maintenance is that if these chips are sealed with vinyl,

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it is necessary to observe whether the tin is blown off

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Especially when soldering the periphery of the chip,

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incorrect temperature and method will cause the baseband or baseband running memory to explode

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Or there is a false soldering of these two chips

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At this time, you only need to re-solder the baseband CPU or baseband running memory,

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and the general fault can be repaired

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Double-layer mainboards, such as Huawei's nova 6, have been dropped,

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and its non-baseband failure usually requires re-soldering the middle frame

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This is the welding position of its middle frame

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This is the upper mainboard

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After the mobile phone is dropped,

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the solder joints on the middle frame corresponding to the lower mainboard are easy to drop

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For example, in the picture, the pads here are all dropped

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Dropped points will lead to no baseband, you only need to remove the upper layer and the middle frame,

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and make up for the dropped points on the lower layer

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Then reinstall the middle frame and the upper layer, basically it can be repaired

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This is the solder joint corresponding to the middle frame on the repaired mainboard

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That's all for this lesson