820-00840

iFix

Member
Hi guys.

First i wanna congratulate to everyone in this community for the progress made with the right to repair 🖖 :cool: .

Now... I have this board A1708 820-00840 which gets 20v powers on fan spins fast and no image no backlight. All diode mode measurements on all Coils are fine and also getting all necessary voltages just not getting backlight and CPU voltages. No liquid spill or corrosion anywhere the board looks like new. Any ideas would be appreciated

Thanks
 

iFix

Member
No repairs done before. I compared to a working board on L7370 pin 1 i should have 6.8v but it's 0v. Also on L7210 and L7220 no voltage i didn't have time today to check I'll see tomorrow...
 

2informaticos

Administrator
Staff member
Stop to check DC voltage on the input pin of the coils from buck converters.
Didn't look strange that value for you?
What is R7370 voltage?

Do you get L7730 and other voltages from pages 61 & 62?
 

iFix

Member
On L7730 i get 1.06v and on R7370 0.72v sometimes it's losing it
PPBUS_G3H_CPU is 13v
L7930 1.8v
L7960 pin 1 0.5v and pin 2 0.9v
L8060 pin 2 it's 1v
L8030 it's 1v
 

iFix

Member
I didn't write:
L8060 pin 1 0.3v
L7960 pin 1 now showing 0.9v maybe i didn't measure good first time.
L7900 pin 1 sits around 2.6v and pin 2 is 1v 🥳
 

2informaticos

Administrator
Staff member
Any reason to continue verifying DC voltage on the wrong pin of a buck converter coil???
As I said, pin 1 (input) is not for DC voltage.
If you don't believe me, use an o-scope and don't waste your time in the future.

Do you get PM_EN_CPUVCC?
If yes, try known good BIOS.
 

iFix

Member
Now even PPBUS_G3H is 0.5 and shows 20v drawn. Type C controllers issues? No short on PPBUS_G3H
 

2informaticos

Administrator
Staff member
What happened to lose PPBUS_G3H?

Post U7000 basic voltages: P_IN, AUX_DET, VDDA/P, AUX_OK, A/BMON.
Remove F7000 and check C7050 voltage.

Does the board turn on with known good battery?
 

iFix

Member
Hi 2informaticos.

The laptop got back the voltages probably the cable was bad. On R7148 both ALL_SYS_PWRGD the voltage goes up to 1.8v and goes down. The signal comes from PMIC...
 

2informaticos

Administrator
Staff member
U7800 requires some power good signals, to release ALL_SYS_PWRGD.
ALL_SYS_PWRGD is pulled-up to 3V_S0 through R7846, check it; should pulse higher than 1.8V.
If all these good, something happens when CPU power supply tries to start.
 

iFix

Member
R7846 on PP3V3_S0 i have 3v and 0v on ALL_SYS_PWRGD. R7846 is 10k as it should be. R7842 is 100k and R7841is 40k instead of 100k
 

2informaticos

Administrator
Staff member
Force the board to S5 state; short SMC_ONOFF_L to ground 5s.
Then trigger SMC_ONOFF_L and check for pulse at ALL_SYS_PWRGD, at same time.
 

iFix

Member
I forced the S5state and now when plugged in i get 3v on button when pressed comes back and i get 1.6v on ALL_SYS_PWRGD and goes back to 0v. Few times stayed longer at 1.6v
 

2informaticos

Administrator
Staff member
1.6V is lower than expected, as it is pulled-up to 3V.
May have a problem with U7800, or other chip connected there; SMC, or PCH.
Be sure all power good signals received by U7800 are good.
Of course, do not expect PM_PGOOD_CPUVCC yet.
 

iFix

Member
I took out and resoldered both U7800 and the SMC still the same. All contact under then are good. It boosts up to 1.9v and stays there. PCH issue?
 

iFix

Member
Just as i wrote the last reply i said let me measure again and i got a fan spin and 3.3v all power good. Now not showing picture :ROFLMAO:
 
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