MacBook Pro A1708 820-00840 - 20v, 0.5a, Fan Spinning

[gap-ruse-pried]

I have a MacBook Pro A1708 non touchbar that wont boot. Getting 20v, but only 0.5a when ssd is disconnected, around .65a when ssd is connected.

Upon plugging in usb c power, the fan spins for 30 seconds then stop. It’ll go again after a little while, but stop again. Like it’s trying to start but can’t.

Tried caps lock and got no light. I do have a usb c to regular usb adapter, so I plugged in a couple flash drives. One of them was blinking rapidly and consistently, the other didn’t blink at all. When I plugged them into my regular pc, they both light up and flashed normally.

Also tried a usb c to hdmi adapter in case it was just a display issue, but I didn’t get an image on the monitor.

I’ve tested some components as noted below:

PPBUS_G3H (F7000) ~13.08 V
PP3V3_G3H (C7080) ~3.42 V
PP5V_S5 ~5.12 V
PP3V3_SSD ~3.32 V
PP1V8_S0 ~1.8 V
PPVCCCPU_S0G ~0.95 V
PPVCCSA_S0G ~1.04 V
L7410, L7420, L730 0 V
SMC_RESET_L ~3.42 V
SMC_BC_ACOK ~3.42 V
PM_RSMRST_L ~3.3 V
PMIC_RSMRST_L ~3.3 V
PM_SLP_S4_L ~3.42 V
PLT_RST_L ~3.32 V

Not sure where to go next? I have experience with microsoldering but mostly on consoles. This is my first time doing any sort of Mac repair, so any guidance is appreciated!

 

[2informaticos]

First of all, welcome to the forum!

Monitor CPU core voltage.
It should drop to 0.65V aprox, after 10-15s; when board really boots.
BTW, it is available at L7210/20 for test.

Do you have known good battery, holding some charge?

 

[gap-ruse-pried]

First of all, welcome to the forum!

Monitor CPU core voltage.
It should drop to 0.65V aprox, after 10-15s; when board really boots.
BTW, it is available at L7210/20 for test.

Do you have known good battery, holding some charge?

Hi, thanks for your reply. I forgot to mention, the battery is toast so it is not hooked up, just running straight from the power adapter.

I measured both L7210/20 and both sides on each are around 0.955v

 

[2informaticos]

Any fault history available?

Both coils are tied together; enough to check one.
BTW, DC voltage must be test on output pin of the coil (only).
Input pin should have similar value, but that is not a real DC voltage; an osciloscope can show you the reason.

0.95V on VCORE means that board doesn't boot, is stuck.
Just in case, monitor its behavior from start until 30-40s.

You can try flashing known good BIOS (U6100).

Please, write directly into bottom reply box, instead of clicking Reply button.
I don't see any reason to quote an entire post, visible few centimeters above.

 

[gap-ruse-pried]

No fault history as far as my friend knows, the only thing he mentioned was he took it to Africa and after charging it there, the next time he tried to turn it on it wouldn't boot and it got very hot. Not sure how helpful or relevant that is though.

It's still 0.95V after 30-40s, even after the fan stops spinning.

Will try flashing BIOS. As I am inexperienced with Macs, is there any downside to flashing, or anything else I should try first?

 

[2informaticos]

Make bakup of your actual BIOS first.

820-00840 8HV22 Medusa clean ME + PRAM.bin

drive.google.com

If the behavior doesn't change with this file, then you have hardware problem...