Hi, another weird problem with a macbook.

I'm trying to repair this Macbook Pro 13" A1708, (820-00840-A) it has no image, but backligth is working ok.

All voltages are good, but has no vcore. L7410, L7420 and L7430 have voltage (cpu vcore) but only for half a second.

The weird thing is that cpu gets hot, and fan spins. (also osx pendrive install usb, blinks as it were booting from it)

Someone experienced something like this?

Could be a damaged cpu or bios corrupted?

Thanks in advance.

Can You connect external display?

Hi Shooter75, yes I can connect an external display whith usb-c to hdmi adapter but there is no image via external.

The point is that without cpu vcore is not possible to guet video, but there is a normal voltage there (at the vcore coils) for a moment.

Thanks for your help.

If video-drain wasn't found at init-algorithm, vcore dosn't appear.

Hi Shooter75, what do you mean with "video-drain".

Could you explain it?

Wich part of the circuit?

Thanks.

Do You understand "video-source"?
Video-drain is antipod of.
Wow - Any external/internal display.
Without any V-D, vcore don't appear.
1. Verify AUX ch at eDP on MB.
2. If no detection packets appears - GT2.eDP channel is damaged.
3. And measure eDP-mux(TB-host), if it has it's power when You connecting external display.
4. If You have same situation with AUX ch at TB-host, - Your GT2 is damaged.

You can backup Your original EFI and try any from 00840 with cleared ME.
This will not to be stable, but You can detect efi-crashes.

Shooter75


Yea, it is clear for me now.

I'm going to test the communication with lcd panel and will post the results.

Thanks again.

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[size=85]Posted after 3 hours 27 minutes 32 seconds:[/size]

Hi, I have measured EDP_INT_AUX_N signal and EDP_INT_AUX_N, and both have a burst of pulses in the boot process.

Probably these pulses don't get its destination to lcd, so I'm going to order the flex cable and test again.

I have also measured pwm circuits for PPVCCGT_S0G voltage, and only get pulses for a moment at pin 1 of coil L7410. Pin 1 of L7420 and L7430 has nothing.

If the new flex video cable doesn't solve the problem, I will investigate if there is a problem with phase 2 and phase 3 of PPVCCGT_S0G pwm circuit.

Thanks and hope to have good news soon.