Why is Honor 50 Lite NTN-LX1 lost sound after liquid penetration

We received a Huawei 50 Lite for repair after minor liquid penetration and a non-functioning speaker. We have faced this problem many times, so we carried out the repair quickly enough.

But at the very beginning we always troubleshoot or identify the causes of the malfunction.

We detach the cover and examine the smartphone. By the red colored indicator in the lower part, we recognize that there was a liquid ingress.

The speaker is located at the bottom of the device and the signal on the tracks on the motherboard passes through the sub-board via the inter-board cable. On the photo we can see that the phone was tried to be repaired in another repair shop, a new speaker was installed and a new inter-board cable was also connected. Just in case we check the resistance on the contacts with a multimeter. Since everything is fine and the signal passes, the fault can only be somewhere on the motherboard.

We examine the motherboard, and on the photo, we can see spots as a consequence of liquid on the side of the upper right corner.

We unsolder the metal shield protecting the chips. It is obvious that the liquid got in and oxidized in the area of the WCD9370 audio chip.

We remove the chip using a soldering station, where we can also see that one of the contacts under it is burned out as a result of a short circuit.

We restore the damaged contact, namely, under a microscope, with a sharp scalpel we clear the place of breakage and restore the contact with a thin copper wire.

The chip itself is damaged as well and it will not be possible to restore the contacts, so install a new one from the donor-motherboard.

Install the audio chip on the board.

After installing the new chip, according to the results of the tests, we have stated the fact that the speaker started to work again and reproduce sounds without distortion. Let's move on to the final stage ("finishing"). We wash off the flux with an alcohol cleaner for electronic equipment, attach the contact with an ultraviolet mask, put back the metal shield and reassemble. Done!

Useful fact for the technician.

The other day also brought to repair Honor 50 Lite, with a non-functional microphone, while the both speakers work without any problems! And what would you think, the problem was in the same spot!

As it turned out, the same contact under the chip was damaged, except that it was not necessary to restore the contact on the board, after cleaning and re-rolling the chip, the microphone started working.

Looked at the device from the inside, there is practically no evidence of moisture anywhere, only on this chip. But not only inside! There are no traces of liquid anywhere under the cover and it seems that the liquid penetrates through the hole for the second microphone on the top end of the phone. See :)?!