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A1398 - 820-00138 - No display and Fan on high speed.

R

ronaldo

Member
Hi everyone.
I need help with this Mac, please.

No signs of liquid, no short on the board.
It turns on, but will not display. The fan goes to high speed.

L3095 - 0V
L7520 PP5V_S4 - 5.05
L7130 PPVBAT_G3H_CHGR_REG - 12.59V
L7560 P3V3S5_LL - 3.32V
L7630 PP1V05_S0_REG_R - 1.05V
L7430 vPP1V35_S3RS0_CPUDDR - 1.36V
L7870 P1V5S0_SW - 1.51V

L7310 PPVCC_S0_CPU_PH1 - 0V
L7320 PPVCC_S0_CPU_PH2 - 0V
L7330 PPVCC_S0_CPU_PH3 - 0V

I assumed that CPU MOSFETs were faulty and replaced all of them, but still the same issue.

Please can someone help me?
Thanks
 
2informaticos

2informaticos

Administrator
Staff member
You can't expect the board to boot, without CPU core voltage.

CPU power supply needs more than a simple enable signal.
PCH, BIOS and CPU are all involved there.

What voltages and signals, did you check before replacing U7310/20/30?
Did you replace with proper chips, or still used the f***g FDMF6808?

Check voltage on pins 1, 3, 7, 8 of U1950.
 
R

ronaldo

Member
Yes, the CPU is not getting any voltage and surely it will not boot.
I just replaced it as a guess that MOSFETs was faulty.
New MOSFETs are DC15AD - DMF3030.

U1950
Pin 1 - 2.25V ~ 2.50V
Pin 3 - 0V
Pin 7 - 0V
Pin 8 - 3.42V

Just a doubt, does this board require a battery connected to turn on?
 
2informaticos

2informaticos

Administrator
Staff member
Is good to connect known good battery, to discard such issue.
It should boot on charger alone, but sometime not (reported by more people).

Inspect U1950 for corrosion; remove it and check underneath.
Change it, just in case.
 
R

ronaldo

Member
After replacing U1950 the board started to get 1.77V on U7310/20/30.
But the fan is still high speed and has no display.

I've tested with another battery and same results.
Something I've noticed is that even with the fan on high speed the heatsink is burning hot, but this happens with the second battery.
 
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