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MacBook Air (A1932 | 820-01521-02) - No image no backlight

HeyWatchOutDude

HeyWatchOutDude

Member
Hi,

Video:
https://imgur.com/a/x2A2qk9

I can successfully restore the BridgeOS (T2) via DFU mode but still no image on the screen, the S0 power rails are (kinda) present. I don’t think that’s a backlight issue because I have checked it with a flashlight still can’t see anything on the screen.

- PP5V_S0_BKLT_D = 5V
- PP5V_S0_BKLT_A = 5V
- PPVCORE_S0_CPU_PH1 = 0.6V
- PPVCORE_S0_CPU_PH2 = 0.6V
- PPVCCGT_S0_CPU_PH1 = 0V
- PPVCCGT_S0_CPU_PH2 = 0V
- PP0V95_S0_CPUVCCIO_REG_R = 0.95V
- PPBUS_G3H = 12.58V (whcih

Note: Screen is good.
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

CPU core voltage looks good, board seems to boot.
Check external video and USB activity.
 
2informaticos

2informaticos

Administrator
Staff member
Trackpad clicking and USB-C power light on are irrelevant.
But Caps Lock light reaction confirms that the machine boots and doesn't get stuck.

Disconnect internal LCD and check again for external video.

BTW, write directly into Reply box, instead of clicking Reply button.
Unless you see any reason to quote an entire post, visible few centimeters above.
We try to maintain the forum aesthetic...
 
HeyWatchOutDude

HeyWatchOutDude

Member
internal display disconnected but still no image on the external display. (Rebooted MacBook)

Note: Adapter, HDMI cable and external display are working. (Verified it with my MacBook Pro)
 
2informaticos

2informaticos

Administrator
Staff member
Did restore, or revive in DFU?
Just in case, try PRAM reset too.

Any history fault?
Check for liquid signs on audio board (both sides) and cable.
 
HeyWatchOutDude

HeyWatchOutDude

Member
did restore and revive via DFU. (No problem overall)

Already tried PRAM reset, no success :/

History:
Waterdamage | Short on PPBUS_G3H and defect CD3215, fixed it. As you can see on the ampere meter the board is booting (20V/0.3-0.4A)

No water damage on the audio board (both sides). Btw why is it necessary? It should also show something on the screen without it.

edit:
I’m a little bit concerned about the voltage of the PPVCCGT_S0_CPU …. Related to the repair wiki it should be 0.75V. (Source: https://repair.wiki/w/A1932_2018_-_2019_MacBook_Air - power sequence) … mine is 0V.

CPUCORE_PHASE1 = cant measure it .... AUTORANGE is looping on my multimeter but PPVCORE_SO_CPU_PH1 is present....strange.

edit2:
Maybe the U7100, U7410 or U7430 are faulty?

U7100:
- CPUGT_IMON = 0V
- CPUGT_NTC = 0.8V
- CPUGT_COMP = 4.6V
- CPUGT_FB = 0V
- CPUGT_RTN = 0V
- CPUGT_ISUMP = 0V
- CPUGT_ISUMN_R = 0V
- CPUGT_ISEN1 = 0V
- CPUGT_ISEN2 = 0V
- CPUGT_FCCM = 5V
- CPUGT_PWM1 = 5V
- CPUGT_PWM2 = 5V

U7410/U7430:
- CPUGT_PHASE1 = 0V
- CPUGT_PHASE2 = 0V
- PP5V_S0_CPUGT1 = 5V
- PP5V_S0_CPUGT2 = 5V
- CPUGT_BOOT1_RC = 0V
- CPUGT_BOOT2_RC = 0V
- CPUGT_BOOT1 = 4.6V
- CPUGT_BOOT2 = 4.6V
- CPUGT_GL1 = 0V
- CPUGT_GL2 = 0V
- PP5V_G3S = 5V
- PPBUS_HS_CPU = 12.58V

I assume PPVCCGT_S0_CPU is important for the internal GPU, isn’t it? So in my case the GPU has no power which explains the no image issue. Do you agree?

Should I start with replacing "U7100"?
 
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2informaticos

2informaticos

Administrator
Staff member
iGPU voltage appears when high graphics load is detected.

"CPUCORE_PHASE1 = cant measure it .... AUTORANGE is looping"
Never try to measure DC voltage on the coil input; an o-scope shows you why!
DC voltage is present on the output pin of the coil, where the filter cap is placed.
Sometime you can find almost the same DC reading on the input pin; depending which power supply is.
However, that is not the correct measurement point; you've just seen that.

"No water damage on the audio board (both sides). Btw why is it necessary?"
I didn't say is necessary.
But many 01521 boards get T2 damaged because of leakage from audio board/flex.
Look at pins 33 & 35 of J6100; hope you understand what I mean.
This fault was several times mentioned on the forum.

"As you can see on the ampere meter the board is booting (20V/0.3-0.4A)"
That is not 100% confirmation.
Caps Lock light reaction is the best confirmation in this case.

However, missing internal/external video at same time points to iGPU problem.
 
2informaticos

2informaticos

Administrator
Staff member
You didn't mention U6400 corrosion before!

Very likely T2 has internal damage.
Was the reason I asked about audio board and flex.
But U6400 can cause same problems as the audio amplifier placed on audio board too.
T2 signal lines are placed next to PPBUS_G3H underneath U6400.
I'm sure you will find short, or low values to ground on that lines.
 
2informaticos

2informaticos

Administrator
Staff member
Just point one ball close to PPBUS_G3H and follow the lines in boardview.
If goes to T2 and you have an access to check it on the board, that is luck.
If not, can only be check without U6400 on the board.
Was you needed to do before soldering new chip...
 
HeyWatchOutDude

HeyWatchOutDude

Member
I have now checked the following pads under the U6400. (diode mode)

- PP1V8_S0_SPKKRAMP_AVDD = 0.328
- SPKRAMP_L_AREG = OL
- SPKRAMP_L_DREG = OL
- I2S_SPKRAMP_L_R2D = 0.487
- I2S_SPKRAMP_L_BCLK = 0.488
- I2S_SPKRAMP_L_D2R_R = 0.499
- I2S_SPKRAMP_L_LRCLK_R = 0.488
- SPKRAMP_INT_L = 0.466
- SPKAMP_L_MODE = OL
- SPKRAMP_RESET_L = 0.462
- SPKRAMP_L_OUTP = OL
- SPKRAMP_L_OUTN = OL
- SPKRAMP_L_BSTN = OL
- SPKRAMP_L_SNSP = OL
- SPKRAMP_L_SNSN = OL
- I2C_SPKRAMP_L_SCL = 0.467
- I2C_SPKRAMP_L_SDA = 0.467
 
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2informaticos

2informaticos

Administrator
Staff member
Are these voltages, or diode mode readings?
Multimeter shows "V" on diode mode, but NEVER write it when you post diode mode values.
Avoid confusions, please.
Also, "0V" means short in diode mode; are you sure is not OL instead?
 
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