Macbook 2017 with touchbar (A1706) won't turn on after removing the screen

[Ryan.man]

Hello everybody! Posting this in hopes somebody has some expertise that leads to a clear path of troubleshooting that saves me a lot of time!

My macbook has the flex cable problem, the one that prevents the screen turning on. Ive been dealing with this for the last 3 years. Last year it went dead and I managed to fix it following youtube tutorials. But my fix wasnt the best, the problem returned a month later. This week, it went dead again. I again tried to fix it.

This time the original cable broke too close to the screen, it can't be fixed without tearing the screen apart. Ok, I can't do this right now, so I decided to use the macbook without the screen. I turned it without the screen while it was still disassembled, the antenna was connected with some of the screws. It worked great with an external screen. Up to now, all is good 😁

Then it started to happen. I am not sure what.

I decided to put all the screws I could back to their places, even without the screen, so they would not be lost somewhere else. I turn it on again and this time the Apple logo appears but that's it. It won't boot anymore. Just stays on Apple logo. I have windows on bootcamp, so I try to boot into it. The boot menu (to choose the disc to boot) works fine, I select Windows, and then I get a black screen. Nothing happens. Nor Windows nor Mac OS boots.

It was working fine without the screen just minutes ago. I just put some new screws to their locations...

I remembered I had a similar problem like this last time I was fixing the screen (difficulty booting with an external screen), so I decided to put the screen back on.

I disconnected the antenna again, reinserted the screen, reinstalled the antenna, put all screws back on. I am not sure if I did this with the battery connected, I think I might have forgotten to disconnect it. I might have let a screw or two fall into the board, I am really not sure.

When I finish mounting it, I turned it on again and then... Nothing happens. The usb adapter I use to connect the external display and a mouse has a led. The led turns on when I press the power button, but then it turns off and after a while it turns on again... It looks like there is some problem preventing it to fully energize the system and it is resetting. The mouse, which in normal conditions would turn on when the boot started, won't turn on anymore. The external screens receives no signal.

I tried disconnecting everything again. I turn it on without antenna and screen. Now the usd adapter led just turns on and keeps that way. But devices connected to it do not receive power. Looks like the motherboard does not energize everything. If I let it on for a while, the fans will start rotating. But that's it. Not even the CAPSLOCK led turns on.

This is the current state of the machine 😥

I am hoping it is a stupid problem since it was working fine. I am hoping I did not burn any sensible chip with ESD or created a short working with the screws with the board turned on.

I am trying to troubleshoot it with the schematics and board, but if anyone with experience on macbooks faulty logic boards could drop an insight I would be very happy.

Thank you in advance!

[mon2]

What is the voltage to ground of PPBUS_G3H @ F7000 (white fuse)? Check both sides of the fuse. This is the primary power rail.

[Ryan.man]

Hey, thank you for your prompt response!

I am a bit in a hurry with daily activities, I did not have much time delving into schematics, but I was able to measure what you asked for. It is giving me 10.5V on both sides. Not sure if this is too low, as it seems it should be a bit over 12V.

Could you give me some tips on which components/power lines/data lines I should check first to be sure it is being correctly energized? I greatly appreciate your input!

[mon2]

This is a low voltage. Remove all power. Disconnect the battery. Meter in resistance mode. Measure the resistance to ground of the same fuse. We are checking if there is an excessive load on this main power rail which is causing this voltage to be pulled down. What is the resistance (in ohms) to ground of this junction?

[Ryan.man]

Oh, I should have mentioned before: I measured the 10.5V with the macbook turned on. Now I measured it while macbook was shut down and it was 11.64V.

I just measured the resistance without a power source (battery disconnected). It looks like it stabilized around 190k ohms, after capacitance transient is gone.

[mon2]

Voltage of PPBUS_G3H should be in the 12-13v range.

Flux and remove the fuse @ F7000 to isolate the PPBUS_G3H power rail producer (U7000; ISL9239) and the rail consumer (downstream loads). Then power up again. Suspecting the rail will still be as reported but best to stabilize this power rail without a load and then introduce the fuse back again.

Measure the voltage to ground of the following:

SMBUS_SMC_5_G3_SDA
SMBUS_SMC_5_G3_SCL

the above are the 2 SMBUS / I2C lines being used by the ISL9239 for the buck / boost operation.

Would you have a USB Type C meter? If not, consider to source one from Amazon or similar. They are relatively inexpensive and will help in the debugging. Of interest is the voltage and current draw from the USB type C power adapter of this logic board.


reference reading:

https://repair.wiki/w/MacBook_Pro_A1..._at_20V_repair

[Ryan.man]

I don't have the USB-C Meter, I'll buy one. I won't be able to work on this till Monday, so next time I'll probably have it already. I still did not take the F7000 fuse out.

The measurements I did before were taken with the logic board still connected to the whole case (including the antenna and the screen).

Now I removed the logic board entirely and I got the following values when turning it on by plugging the original charger to a usb-c port:
(F7000 is still on the board!)

PP20V_USBC_TA_VBUS_CONN	20V
PPBUS_G3H	13.02V
SMBUS_SMC_5_G3_SDA	3.39V
SMBUS_SMC_5_G3_SCL	3.39V
PM_EN_P3V3_G3H	5.08V
PPVIN_G3H_P3V3G3H	19.75V
P3V3G3H_LX	8.4V
P3V3_G3H_REG_R	3.4V

Questions:
1) Since I do not have the USB-C Meter yet, I thought that PP20V_USBC_TA_VBUS_CONN would give me the voltage the original charger is giving to the board. Am I correct? If yes, it looks like the board is getting full power to work with, right?

2) The CPU is getting very hot. Is it safe to keep it turned on while making measurements when the board is disconnected from the fans?

I took some measurements on U6903 and although the output P3V3_G3H_REG_R looks fine, I am not sure the inputs are in the correct range:

3) PPVIN_G3H_P3V3G3H should be this high? Schematics says it should be around 8.6V...

4) PM_EN_P3V3_G3H should be this high? I was thinking it should be around 3.3V...


Any new inputs are appreciated. I'll come back to work on this on monday probably!

[Ryan.man]

Voltage of PPBUS_G3H should be in the 12-13v range.
reference reading:

https://repair.wiki/w/MacBook_Pro_A1..._at_20V_repair

I did look at the suggested reading.

=> Check for 0.4 V in diode mode on SMBUS_SMC_5_G3H_SDA and SMBUS_SMC_5_G3H_SCL (red probe on GND)

My multimeter gave me 0.445V for both lines. I guess this is ok, right?

The other suggestions on that wiki gave normal readings.

[mon2]

2) The CPU is getting very hot. Is it safe to keep it turned on while making measurements when the board is disconnected from the fans?

No, it is not safe. The heatsink and fans serve a purpose. If they could have been removed, Apple / Foxconn would have done so to save a few pennies. Without the heatsink and fan, the CPU can burn out.

The PPBUS_G3H is now normal. What changed? Attach it back to your hardware and see if the unit boots.

[Ryan.man]

Doesn't the board have a circuit to reduce cpu clock when its temperature is too high? Well, even if it has, I can't be sure it is working correctly...

Anyway, good thing that I was turning it off right after measuring, then. I don't think cpu temperature went over 70 degress celsius because I was still able to put a finger on the heatsink without burning myself.

The PPBUS_G3H went normal when I measured it with the board disconnected from everything and powered only by the original charger.

Before, when I got 10.5V, it was powered by the battery and with all peripherals connected to the board...

I know it is still not booting even with 13V on PPBUS_G3H because my mouse connected to the USB-C port won't turn on as it used to do when it started booting.

[Ryan.man]

So, I had some time to check a lot of signals and I have still not give up trying to find the problem here, although I'm getting less hopeful as I dig through.

I checked the voltages of all power lines listed on the "power aliases" page of the 820-00923 schematics and all of them seen fine:

PPBUS_G3H 13.02
PPBUS_HS_CPU 13.02
PPBUS_HS_OTH5V 13.02
PPBUS_HS_OTH3V3 13.02
PPBUS_S4_HS_TPAD 13.02
PPDCIN_G3H 20

PP3V3_G3H 3.3
PP3V3_G3H_SMC_ISNS 3.3

PPVCCIO_S0_CPU 0.956
PPVCCPRIMCORE_SUS_PCH 1.00
PP1V2_S3 1.20
PP1V2_S3_CPUDDR 1.2
PP1V8_S4 1.80
PP1V8_S3 1.79
PP1V8_S0 1.79
PP1V0_SUS 1.00
PP3V3_S4_SOC_PMU 3.34
PP5V_S5 5.12
PP5V_S4 5.13
PP5V_S0 5.12
PP3V3_S5 3.35
PP3V3_SUS 3.34
PP3V3_S4 3.35
PP3V3_S4_BT 3.34
PP3V3_S4_TPAD 3.34
PP3V3_S5_SSD 3.34
PP3V3_2V7_NAND_VCC 2.68
PP3V3_S0 3.32

PP3V0_G3H 3.06
PP1V2_S0SW 1.19
PP0V6_S0_DDRVTT 0.59
PP0V6_S3_MEM_VREFDQ_A 0.60
PP0V6_S3_MEM_VREFCA_A 0.60
PP0V6_S3_MEM_VREFDQ_B 0.59
PP0V6_S3_MEM_VREFCA_A 0.59
PP1V8_SUS 1.79
PP1V8_S3_MEM 1.79
PP1V0_SUSSW 0.99
PP1V0_S3 0.99
PP1V0_S0SW 0.99
PP3V3_S5_T139 3.36
PP5V_S0_KBD 5.12
PP3V3_TBT_X_S0 3.33
PP3V3_TBT_T_S0 3.32
PP3V3_S5_SSD_LB 3.34
PP3V3_S4_MESA 3.35

PP1V8_S0SW_DFR 1.8
PPVCCSA_S0_CPU 1.04
PPVCC_S0_CPU 1.19


The only exception appears to be PPVCCEDRAM_S0_CPU, which is 0 and, for what I understood, should be 1.05V. This signal is produced by U7760, so I proceeded to check its voltage signals:
PP5V_S0 5.12
PM_OPC_ZVM_L 0
SWEOPIO_CNFG 0.1
PPVCCEDRAM_S0_REG_F 1.04
SWEOPIO_G 0
PPVCCEDRAM_S0_CPU 0

I couldn't find the datasheet for this chip (SLG5AP031), but I did find one for SLG55031. 55031 says EN is activated with a HIGH signal. But because PM_OPC_ZVM_L (which connects to EN pin) is named ending with "_L", I'm assuming SLG5AP031 should be enabled by LOW signal. If yes, then the chip should have worked fine and PPVCCEDRAM_S0_CPU should have followed PPVCCEDRAM_S0_REG_F voltage. If my reasoning is correct, then either U7760 and/or Q7760 and/or Q7761 are not working correctly...

If this is the case, is there an easy way to check which is failing?

Do anyone has any tip about what else should I check?

If the CPU is bad, is there an easy way to test it?

I'm thinking about buying a working macbook equivalent to this one to cross check all signals in the hopes I can discover what is wrong. Not sure it is worth investing so much money and time on this, though.

Thanks for any inputs on this!

[mon2]

See if the attached helps.

[Ryan.man]

Thanks for the tip, the first stage (that generates the main power rails) is working nice. I'll check later for some of the intermediate signals at next stages. I already know PPVCCSA_S0_CPU and PPVCC_S0_CPU both look ok, and that PPVCCGT_S0_CPU is always 0, but I read somewhere that this last signal will only activate when there is demand for graphics.

I'm still suspecting my eDRAM is not being powered up. Is there any other diagram like those you've sent me that shows PPVCCEDRAM_S0_CPU being generated?

[Ryan.man]

Do you have access to chinafix.com? I tried searching for PPVCCEDRAM_S0_CPU and I found a promising discussion that I'm unable to read as a new member :/

https://www.chinafix.com/thread-1265122-1-1.html

[mon2]

https://boards.rossmanngroup.com/thr..._s0_cpu.41372/