820-02098 Liquid damage, no audio from internal speakers

[tcampbell34]

This board had some pretty bad liquid damage and partial short on PP3V8_AON. Almost every component on the board had some level of corrosion on it. The worst areas were around the ISL9240, the 3v8_AON MOSFETs and the speaker amps. I had to replace the ISL and almost all the caps and resistors around it. Replaced all the 3v8_AON MOSFETs and U5700. Replaced U8100 and UR760 also and had to run a wire to reconnect P3V8AON_PWR_EN. It finally now turns on and boots to the OS, but no sound from the internal speakers. When I attempt to play a video on YouTube, the video itself freezes as soon as it begins and then the video turns black. I can still see its playing because the time keeps going, but no sound comes from the speakers. If I connect headphones and try again, the video now plays fine and I do get good sound from the headphones. When you unplug the headphones, I do not get any sound from the internal speakers and the YouTube video freezes and the video goes black again. I checked the voltages and signals below and they seem fine and I do not find any shorts around the speaker amps. I do not get any voltage on the any of the amp outputs.

PPBUS_AON - 12.01v
PP3V8_AON - 3.8v
PP1V8_AWAKE - 1.8v
PP1V2_AWAKE - 1.2v
SPKRAMP_RESET_L - 1.2v
SPKRAMP_INT_L - 1.2v

 

[2informaticos]

Check diode mode to ground on the SPKRAMP_ data lines.

 

[tcampbell34]

I2C_SPKRAMP_L_SCL - 0.319
I2C_SPKRAMP_L_SDA - 0.317
I2C_SPKRAMP_R_SCL - 0.317
I2C_SPKRAMP_R_SDA - 0.317

 

[2informaticos]

I was expecting to know more about RESET, INT and other related lines.
You need to check all the lines between T2 and audio amps...

 

[tcampbell34]

This is a 14" M1, so there is no T2, but I checked all the lines that go from the speaker amps to the M1 and they seem fine and match with a good board.

I2C_SPKRAMP_L_SCL - 0.319
I2C_SPKRAMP_L_SDA - 0.317
TDM_SPKRAMP_L_BCLK - 0.339
TDM_SPKRAMP_L_FSYNC - 0.338
TDM_SPKRAMP_L_R2D - 0.338
TDM_SPKRAMP_L_D2R - 0.313

I2C_SPKRAMP_R_SCL - 0.317
I2C_SPKRAMP_R_SDA - 0.317
TDM_SPKRAMP_R_BCLK - 0.336
TDM_SPKRAMP_R_FSYNC - 0.338
TDM_SPKRAMP_R_R2D - 0.338
TDM_SPKRAMP_R_D2R - 0.313

SPKRAMP_INT_L - 0.327
SPKRAMP_RESET_L - 0.327
SPKRAMP_ICC - 0.416

 

[2informaticos]

Both audio channels have the same issue?
You may try to change the others audio amps.

I suspect more damage caused by corrosion.
Maybe internal M1 issue...

 

[tcampbell34]

Yea both left and right audio have the same issue. I removed all 6 amps from the board and it still doing the same thing. I obviously get no sound without the amps but I can tell the computer is still freezing when you try and play sound. everything works fine with head phones though. Any idea what signals to check from the M1? I cannot find anything that seems off compared to a good board.

 

[2informaticos]

If you have good working board, compare voltage level on the signals related with the speaker amps.

I still suspect that leakage from PPBUS_AON (undeneath audio amp) caused damage on M1 lines related with the audio amps.

 

[tcampbell34]

Yea I compared voltage with the good board both without sound playing and with sound playing and the bad board has 0v on most of them when the good board does not. Seems like damage to the M1, but its just weird how I cannot find any rails or signals that are shorted, or even low diode mode. Also strange that both left and right speakers have the same problem. It works perfectly fine with headphones connected also, so is it possible to trick the mac to output the audio from the headphone jack to the internal speakers instead? I know I would probably lose headphone functionality, but I would rather have working internal speakers then a working headphone jack.

Good Board	No sound	Playing sound
I2C_SPKRAMP_L_SCL	1.22v	1.22v
I2C_SPKRAMP_L_SDA	1.22v	1.22v
TDM_SPKRAMP_L_BCLK	0v	.603v
TDM_SPKRAMP_L_FSYNC	0v	5mv
TDM_SPKRAMP_L_R2D	0v	fluctuates
TDM_SPKRAMP_L_D2R	0v	.460v
I2C_SPKRAMP_R_SCL	1.22v	1.22v
I2C_SPKRAMP_R_SDA	1.22v	1.22v
TDM_SPKRAMP_R_BCLK	0v	0.601v
TDM_SPKRAMP_R_FSYNC	0v	4.9mv
TDM_SPKRAMP_R_R2D	0v	fluctuates
TDM_SPKRAMP_R_D2R	0v	.430v

Bad Board	No sound	Playing sound
I2C_SPKRAMP_L_SCL	1.22v	1.22v
I2C_SPKRAMP_L_SDA	1.22v	1.22v
TDM_SPKRAMP_L_BCLK	0v	0v
TDM_SPKRAMP_L_FSYNC	0v	0v
TDM_SPKRAMP_L_R2D	0v	0v
TDM_SPKRAMP_L_D2R	0v	0v
I2C_SPKRAMP_R_SCL	1.22v	1.22v
I2C_SPKRAMP_R_SDA	1.22v	1.22v
TDM_SPKRAMP_R_BCLK	0v	0v
TDM_SPKRAMP_R_FSYNC	0v	0v
TDM_SPKRAMP_R_R2D	0v	0v
TDM_SPKRAMP_R_D2R	0v	0v

 

[2informaticos]

L/R speaker and headphones audio channels come out separately from M1.
Headphones data lines carry both L/R channels.
Speaker channels have dedicated data lines for L/R.