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820-00281 no SUS voltages

N

Narek

Member
I'm working on 820-00281 board which is not turning on. Customer states, that it just died with no reason. There is no liquid or physical damage, no corrosion, no other repair attempts. Board switches to 20V but gets stuck at 0,04A. The PP1V8_SUS and PP3V3_SUS are missing, no shorts. Also PM_SLP_SUS_L is low with 0,003V.

PPBUS_G3H - 12,57V
PP3V3_G3H - 3,41V
PP3V3_S5 - 3,30V

U7800 and the area around looks really good, but I have replaced it just on case with no result.

PPBUS_PMIC - 12,57V
PP3V3_PMICLDO - 3,29V
PP5V_PMICLDO - 5,00V

On thermal camera I can see, that PCH get slightly warmer in two areas amd my guess is PCH is dead. Maybe you have other suggestions?
 
2informaticos

2informaticos

Administrator
Staff member
PCH should be cold in this stage.
Check diode mode to ground on all coils, especially PCH and CPU; compare with good board.
 
N

Narek

Member
After I have posted this thread I have discovered, that PP1V0_SUS / PP1V_PCH_REG_R are shorted - 0,000V in diode mode and 0,001 Ohm. If I inject 1V, board takes ~0,3 - 0,5A but nothing really gets warm, even PCH. I have lifted up L8000 and short appers to be at PCH side.
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
Two power rails shorted denote a problem with the common point, PCH.
You can't heat anything with 0.5W; maybe IR camera sees very small difference between PCH and rest of the MLB.
 
N

Narek

Member
So I have replaced PCH, both PP1V0_SUS / PP1V_PCH_REG_R lines are now present, nothing shorted. Board starts, CPU VCORE is present, all S0 voltages too but there is no video, no chime, just clicking trackpad. Board takes ~1A from charger. I have already tried new bios found on this forum, but it hasn't changed anything. Could you please share known 100% working bios with clean ME?
 
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