SOLVED: A1990 820-01041 No Audio, Macbook Speakers detected under Sound settings after liquid spill

[it-solve]

Very heavy liquid damage around U6300, U6500/50, and whole bottom edge of the board. Some around right USBc ports but they seems to charge
Charge chip was blown, replaced/

Now Mac turns on and everything seems ok, apart than sound.

Replaced U6300 and U6550 as I have 0.88Ohm resistance on PP1V8_G3S as well as SPKRAMP_RW_AREG

Any suggestion what chip controls the audio output? I get 1.8V lines on the PP1V8_G3S

 

[2informaticos]

Audio amplifiers are connected directly to T2.
Any leakage from PPBUS_G3H to data lines (underneath audio amplifiers) can damage T2.

Compare diode mode readings around left/right channels.
Pay atention to SPKRAMP_RESET_L.

 

[it-solve]

Device turns on and works. Except audio. Would T2 partial failure allow system to work ok?

 

[2informaticos]

Why not?
It has a lot of embedded functions.

 

[it-solve]

I have Replaced U6500 and no low resistance at SPKRAMP_RW_AREG anymore
SPKRAMP_RW_AREG - 0.55Vdc
SPKRAMP_RESET_L - 0.048V - ..._L should stay low to operate right?

I cant make sense of it. Diode readings are similar to another board I have. Also, to the left side channels.
Cant figure out if issue is with ADC or Amplifiers. Or T2 as you said. Its pity that I managed brought it back to life, but cant sign it off as completely repaired.

 

[2informaticos]

"_L should stay low to operate right?"
Not really; did you ever seen a device operating in reset mode?

Do you get headphones sound?

 

[it-solve]

What I was referring to was in general. If a signal has _L or _H in the end does it means that to be enabled it needs low or High? Or does it means that it stays at that level as default and needs to flip to operate. I could not find reference to this and is not clear to me.

So basically SPKRAMP_RESET_L stays as LOW (let say under 5 or 1.8 depending on the VCC line mostly) by default and to reset the system needs High? Would that be a reasonable explanation of .._L/H signal lines?


"Do you get headphones sound?" - Yes via the headphone jack, also USBc to 3.5 too.
Systems detects also Macbook Speakers - Built-In. Just no sound on either L or R speakers or tweeters.

 

[2informaticos]

I saw this symptom several times, always caused by SPKRAMP_RESET_L line damage.

Yes, "_L" means active low signal.
But you should understand what is desired state of the signal.
Do you really want to keep it in reset (low)?
Your interest is to disable it, in this case (high).

SPKRAMP_INT_L may also cause problems.
You should compare diode mode readings on the components around all audio amplifiers.
I recommend you to change ALL of them.

 

[it-solve]

Although the measurements were identical to a comparison board, something in U6500 was holding SPKRAMP_INT_L low which must be the reason it was detected but not operating either of the channels. Although I reballed both amps. Went and replace it and now sound is back.

For reference - SPKRAMP_INT_L - 1.8V when audio is working. Added to FlexBV but not sure if automatically pushes is to the online database.

Thanks again