MBA 13" A1392 No Audio After Liquid Spill

[MobileXT]

I have a MacBook Air 13" 2019 Board number 820-01521 has a liquid spill under J6620, C6405, C6416 also the Right I/O speaker board was also water damage but its already been replaced with a new one. After clean the Area by J6620 computer turned on as normal but the problem is no Audio from the left and right speakers. I do have audio coming from the headphone jack but no internal speaker. I also check the speakers and it seams to work. I attached the Schematic and Board view. Thanks!

schematic - https://www.badcaps.net/forum/showthread.php?t=77777
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[mon2]

Re: MBA 13" A1392 No Audio After Liquid Spill

Check the voltages on U6400 = amplifier for the speakers. Sheet 53.

Respectively, this amplifier is configured (volume, etc.) over the I2C bus (SDA / SCL) lines. Check for activity on the I2C bus.

This amplifier has a specific hardware address and the I2C master controller will need to locate (ping) this I2C slave to select the default amplification, etc.

Check for the presence of the required I2C bus pull-up resistors @ R5300 & R5301 (sheet 46).

The I2C interface is open-drain. If these required pull-up resistors are not present then this I2C network will NOT have a defined logic HIGH. In open drain, there is a LOGIC LOW and then OPEN DRAIN = 'high impedance / hi-z'. The referenced resistors are required to pull these floating lines for the logic high.

Confirm the resistors are not shorted / eroded / missing due to liquid damage.

Do the same check on R5305 and R5306.

Check that J6100 is clean of all residue.

[MobileXT]

Re: MBA 13" A1392 No Audio After Liquid Spill

Check the voltages on U6400 = amplifier for the speakers. Sheet 53.

Respectively, this amplifier is configured (volume, etc.) over the I2C bus (SDA / SCL) lines. Check for activity on the I2C bus.1v8

This amplifier has a specific hardware address and the I2C master controller will need to locate (ping) this I2C slave to select the default amplification, etc.

Check for the presence of the required I2C bus pull-up resistors @ R5300 & R5301 (sheet 46). Both Resistor at 2.2K reading 1v8

The I2C interface is open-drain. If these required pull-up resistors are not present then this I2C network will NOT have a defined logic HIGH. In open drain, there is a LOGIC LOW and then OPEN DRAIN = 'high impedance / hi-z'. The referenced resistors are required to pull these floating lines for the logic high.

Confirm the resistors are not shorted / eroded / missing due to liquid damage.

Do the same check on R5305 and R5306. same 2.2k 1v8

Check that J6100 is clean of all residue.

J6100 is very clean

[MobileXT]

Re: MBA 13" A1392 No Audio After Liquid Spill

Using my Digital Oscilloscope I have 59.52Hz to 60.24Hz on I2C_SPKRAMP_L_SDA Same with reading with the I2C_SPKRAMP_L_SCL.

SPKRAMP_RESET_L = 0.129V

[mon2]

Re: MBA 13" A1392 No Audio After Liquid Spill

The reset is active low. At that low voltage, appears the amp is stuck in reset mode with the logic low ('0').

[MobileXT]

Re: MBA 13" A1392 No Audio After Liquid Spill

So it could be the amp is bad then.

[mon2]

Re: MBA 13" A1392 No Audio After Liquid Spill

So it could be the amp is bad then.

No. This reset# (active low line) is an INPUT to the amplifier chip. Respectively, someone upstream in the schematic is driving this line high or low as required. From the earlier post, this line is being driven LOW and kept LOW so the amp cannot do its job. The reset# line must return to high to start communication with the other parts on the logic board including communication over the I2C bus. The I2C bus is most likely used for the volume control, treble, bass, etc. configuration of this target amplifier. Do not have direct experience with this logic board but this sounds logical so far. Let me see if I can review this board.

Just finished a successful imac repair - what a bear. First the LVDS 30 pin connector was torn off the logic board by a DYI client, then the display would not show anything - because the used ipex 30 pin connector was warped, replaced that from an old t-con board and video worked but then the left side of the display was rather dark. Client bumped the display and nuked the 6 pin backlight connector. Wow. All working now. Will document the process in a fresh thread for future techs. The ipex connector can be sourced from Digikey rather than ordering from Asia.

[mitchw]

Re: MBA 13" A1392 No Audio After Liquid Spill

Hi, I have the exact same board with exact same problem. U6400 was hit with some liquid, but otherwise looks intact.

SPKRAMP_L_AREG that comes out of U6400 has very low resistance (5 ohms) to ground. Can someone confirm what resistance this line has on known good board? Thanks!

[Bubo2020]

Re: MBA 13" A1392 No Audio After Liquid Spill

Hi MobileXT did you resolve audio 820-01521? I have same problem, I think I become crazy to try resolve it. May you tell me how you resolved? Thanks a lot.

[Pedro147]

Re: MBA 13" A1392 No Audio After Liquid Spill

Hi MobileXT did you resolve audio 820-01521? I have same problem, I think I become crazy to try resolve it. May you tell me how you resolved? Thanks a lot.

so you have headphone output but no speakers? Common problem that can be caused by shorted SPKRAMP_RESET_L line under T2. Check if that line is shorted or high?