820-01521 not drawing 20v

Soji

Member
Found short on pp3v3_G3H. Cleared the shot , still 5v no current.
pp3v3_G3H is present
PP3v3_G3H_RTC is present
PP1v8_UPC_XA_LDOA is present
PP3v3_UPC_XA_LDO is present
PP20v_USBC_XA_VBUS is 5v
No PPBUS_G3H
Pls help
 

2informaticos

Administrator
Staff member
"PP3v3_G3H_RTC is present
--------------------
No PPBUS_G3H"
Are you really sure?
3V3_G3H_RTC power supply is powered from PPBUS_G3H, trough R5430.
 

Soji

Member
Sorry my bad. Bad multimeter
PPBUS_G3H present
PP3v3_G3H -1.1v very low🥸
 
Last edited:

2informaticos

Administrator
Staff member
Check first diode mode to ground there; compare with good board.

Post U7650 basic voltages; pins 23, 22, 12, 13, 29, 21.
 

Soji

Member
Resistance 405
Pin 23 -12.31v
Pin 22-3.3v
Pin 12- 0.00v
Pin13-0.00
Pin29-0.00v
Pin 21-0.00
 

2informaticos

Administrator
Staff member
Really strange to get any voltage at L7690, with 0V at pin 21.

Is the machine recognized in DFU mode?
 

Soji

Member
Can u7000 be the problem, because I met some flux around it, probably the technical reflowed it before it got to me.
 

2informaticos

Administrator
Staff member
Check for short on these coils.

Do you get correct 3V3_G3H_RTC for sure?
If yes, check LDO voltages from page 64.
 

Soji

Member
I replaced u7800.
It’s drawing 20v now. But it’s not coming up
The current on the amp meter goes back to zero.
Working around
I found out the some of the coils around the pmic voltages are fluctuating
Like
PVDDCPUAWAKE_SW1/SW2/SW3
The voltage on most of the coils are fluctuating
Thermal camera
T2 is getting warm
Then there is a Pulse on u7800 after 2sec.
 

Soji

Member
PPBUS_G3H and 3V3_G3H_RTC are stable. Is the voltages around u7800 are going up and down.
 

2informaticos

Administrator
Staff member
Compare diode mode to ground readings on U7800 coils with good board.
Do the same for all big coils too.

Reflow U7800, in case didn't solder properly.
 
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