MacBook Pro 2016 A1706 (820-00239) No boot/POST

[reid]

I'm working on a 2016 MacBook Pro A1706 with touchbar, 820-00239 logic board. The board seems to power on and takes about 700 mA from the USB-C port, the CPU gets warm, the trackpad clicks, but there is no chime and the caps lock light doesn't turn on.

The board is in good condition and there is no signs of liquid damage or any damaged components.

I've tried flashing a different BIOS - I'm not 100% sure if the file I flashed was good or if there is ME Region issues, but there was no change in the behavior at all. The SPI termination resistors all seem to be okay.

All voltages seem to be present except both PPVCCGT_S0_CPU, which I think is normal based on reading other posts, and PPVCCEDRAM_S0_CPU, which I'm assuming is the problem. PPVCCEDRAM_S0_REG_R and _REG_F are both 1.05 V.

PPVCCEDRAM_S0_CPU doesn't seem to be shorted, it measures about 100 ohms/0.100 in diode mode. I don't have another similar board to compare this to.

PPVCCEDRAM_S0_CPU voltage seems to be controlled by PM_OPC_ZVM_L and should be turned on when PM_OPC_ZVM_L is high (?). This comes from a level shifter, U7790 which should shift CPU_ZVM_L up to 3.3 V.

The power voltages around U7790 and U7760 all seem to be okay: PP1V0_S3, PM_SLP_S3_L, and PP5V_S0. R7792 measures okay as well.

Both CPU_ZVM_L and PM_OPC_ZVM_L measure 0 V. Diode mode reading for CPU_ZVM_L is 0.295 and PM_OPC_ZVM_L 0.530.

Since CPU_ZVM_L comes directly from the CPU, I'm wondering if it's a bad CPU, but I'm not sure if there is something else that could be causing this CPU output to be low. I haven't tried to remove U7790 yet because it's right below the CPU.

If anyone has any suggestions for further troubleshooting, or if I've misunderstood some of these circuits, your help would be much appreciated! Thanks!

[mon2]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

What is the voltage showing on the Type C port ? Is it 5v or 20v ?

[reid]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

It's 20 V. Starts out around 20 V, 750 mA, then goes down to 680 mA and seems to stay there.

[mon2]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

Your case is listed here:

https://repair.wiki/w/A1706_2016-201...ar_MacBook_Pro

Not charging battery (machine turns on), charger taking 20 V, 700 mA

Continue to post your updates for future readers.

[reid]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

Thanks for the link! I think my board has a different problem. In Louis' video, the board still boots up and seems to work other than not charging the battery.

My board doesn't boot, but seems to charge fine. With the battery plugged in, I get around 1 amp on the USB-C at 20 V, and then it eventually increases to 1.8 amps. The board does respond to the power button, so it can be shut down by holding the button and even when off it still takes about 1.8 amps charging. When I said it was taking 700 mA before, that was with the battery disconnected and the board out of the case. Sorry for the confusion!

The battery was fairly low when I measured, but Q7065 had 11.3 V on source, 2.17 V on gate and 10.75 V on the drain.

There's nowhere to measure PPVCCEDRAM_S0_CPU on the top of the board, so I haven't been able to confirm if that's still 0 V with the battery connected.

[mon2]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

Are you confident that the fault is not just a bad LCD?

If you remove the keyboard and then attempt to boot with a LCD - what are the results? You may have to use tweezers to turn on the logic board. Locate the shorting pads for the on/off function.

The current draw seems respectable for a normal boot, I would say.

Do you have the backlight voltage? (With LCD attached)

[reid]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

The machine could have a bad LCD, I've personally never seen this LCD work and don't have another logic board or screen to test with at the moment. Visually the screen flex cables look perfect and there's no damage to any LCD cables or connectors.

I think I'd need to remove the LCD to be able to connect it to the board outside of the case to measure the backlight voltage, unless there's an easy way to measure on the top/CPU side of the board... I definitely can't see the backlight turn on, and don't see anything on the screen with a bright light on it.

I've tried a few combinations of trackpad, keyboard and LCD disconnected. The LCD cable makes no difference, unplugging the trackpad causes the fans to spin on max, unplugging the keyboard causes no fans because they're powered through that connector.

I've also tried to reset the PRAM with an external keyboard (and with the internal), but it doesn't respond - there's no change in the current drawn and definitely no chime. Since there's no chime, no caps lock activity and no external video output when the LCD is disconnected, it still seems like a logic board issue to me but I'm still new to fixing boards and definitely not an expert.

Thank you for your help!

[iganas]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

Hi reid, I have exactly the same issue on the same board. Have you managed to fix yours?

[reid]

Re: MacBook Pro 2016 A1706 (820-00239) No boot/POST

No I never got it working. I think the last thing I tried was injecting voltage onto PM_OPC_ZVM_L which did turn on the PPVCCEDRAM_S0_CPU rail. But the laptop still didn't boot. I gave up on it but I still have the board so if you figure anything out let me know!

I'm assuming the missing PM_OPC_ZVM_L is a symptom of what the real problem is, and not the problem itself.

[jma46]

Hi, I have a similar problem, the board I have responds to pram reset, the mouse pad feels like its working, the backlight is on but no image? I replaced one of the CPU mosfets which was getting hot, ramps to 20v .8 ma draw then settles around .35ma. Wont boot with touchbar connected, doesnt draw any amps, but seems to be booting unplugged.

Sorry just to add, Caps lock lights up, my next step is to connect speakers and see if it chimes and also any usb activity

[mon2]

Caps lock lights up

press the caps key after you see this led lit. Does the same led toggle on/off? If yes, the operating system has booted and you are at the login screen.

[jma46]

press the caps key after you see this led lit. Does the same led toggle on/off? If yes, the operating system has booted and you are at the login screen.

Hi Mon2 yes caps lock toggles, backlight ok but no image, is it either flexgate on the data cable or something else?

[mon2]

Yes, may be flexgate. Test with an external monitor to be sure.

[Mateusz200]

Hi, did anyone solved problem from this topic? Have same issue with a1706 and running out of ideas.

[mon2]

What is the voltage & current draw showing on your power adapter? 20V ?

What is the voltage to ground of PPBUS_G3H @ F7000 ? (check both sides of this fuse)

[Mateusz200]

there is 20v and around 1A without battery (current is floating after pressing power switch), PPBUS_G3H is 13v

[mon2]

Any liquid damage?

https://repair.wiki/w/MacBook_Pro_A1706_No_image_repair

[Mateusz200]

I got this board from intenet but doesn't seem to by any liquid damage. It's like it turns on and probably post but no image.

[mon2]

Does the keycaps LED toggle after a normal boot time? Any boot chime? Any fan spin? Do you see the mouse LED light flicker if using an external USB mouse? Do you have an external USB hub to test with external video / monitor? Tested with a PRAM reset?

[Mateusz200]

So, I did SMC or PRAM reset, fans starts to spin after power on when cpu gets little hot, no chime and keycaps led, external devices have power, and there is no video on external screen via hdmi. I’ll do smc and pram resets once more just to be sure. Should caps light up even without keyboard backlight?