820-00281-A Getting 19.90V Fans Spinning But not Posting

peeka79

Member
Working on a 820-00281-A A1707 that is getting 19.90V on USB-C Meter and 1.2 amps...it has No Video either on Display Or External Display...You can hear the Charging sound whenever you plug in the Charger but No Video. Caps Lock reacts when fans are spinning but Not Posting. Here are some Measurments.

PPBUS_G3H = 12.57 Stable
PP3V3_S0 = 3.3V Stable
PP5V_S0 = 5.1V
PP3V3_SUS = 3.3V
PP3V3_S0_CPU=0.664V
PP3V3_S0_GPU = 0.00V
PP3V3_S0 = 3.3V
PP1V8_S0 = 1.79V
PPCC_S0_CPU = 0.663V
PM_SLP_S0_L = -0.000

Also Get these Readings...

RA900
Pin 1 - PPVIN_SOGPU_1V8_RC =12.56V
Pin 2 - PPBUS_HS_GPU =12.57

CA905
Pin 1- PPVIN_SOGPU_1V8_RC =12.57V
 

2informaticos

Administrator
Staff member
Any history available, liquid signs?

Missing internal and external video at same time, could be U9800 issue.
Video signals for internal LCD only pass through U9850, but backlight control is processed by U9800.
Could be even both chips affected...
 

peeka79

Member
No Liquid Damage Or noticeable Physical Damage. Also No USB mouse light when plugged in, Just Caps Lock Light reaction when fans are spinning. Could it be the UA900 Chip Since RA900 has 12.7V on Pin 1 And Lin 2 instead of 1.8v that is supposed to be on pin as well as CA905?
 

peeka79

Member
Okay...The only reason I asked is because the ppvin_s0gpu_1v8_rc is Reading 12.7V on RA900 and CA905...So what could be causing the Improper Voltage on that Resistor and Cap?
 

peeka79

Member
Hmmmmm...According to the Schematics ppvin_s0gpu_1v8_rc Should be on Pin 1 of RA900 shouldn?t that be 1.8V and not the 12.57 that I?m getting on both Pin 1 And Pin2? I?m Confused as All Hell now...lol...I?m NOT Saying your Wrong by ANY means I?m just trying to learn :)
 

2informaticos

Administrator
Staff member
Let see...
What voltage do you expect on P1V8GPU_EN, REG_SSTR_P1V8GPU, REG_PHASE_1V8GPU, REG_VOS_P1V8GPU, REG_FB_P1V8GPU???
All have "1V8" in the name...

Do you also expect 1.8V at AGND_P1V8GPU?
 

peeka79

Member
I Apologize if I upset you in anyway 2informaticos as I am just trying to get better at this, and I DO appreciate your expertise as I am Learning...what do you recommend I try ? Thank You for your Patience due to my ignorance and Thank You for Taking the time to help Me...Please let me know :)
 

2informaticos

Administrator
Staff member
You didn't upset me.
I just tried to explain you that 1V8 in the name doesn't imply 1.8V in that line.
Some are signals, other voltages, or feedback, which all reffer to 1V8 power supply.
You can see that all the power supplies have a particular "voltage refference" in the name of their lines.
So, be aware, do not assume things so easy.
This can block you in the way of a repair process.

Do you get voltage at GPU coils at least (LA640/50)?
 
Last edited:

2informaticos

Administrator
Staff member
Good enough to check one pin only for a coil.
Post diode mode reading to ground now (red probe at ground).
If very low value, switch to ohm mode.

Check power rails and enable signal for UA600.
 

peeka79

Member
Hi 2informaticos, Here are the Measurements you asked me to take....

LA640/50 Diode Mode

LA640 Pin 1 1.5 Ohms
LA650 Pin 1 1.2 Ohms

UA600


Pin 35 PPVIN_S0_GFXIMVP_VIN 12.57V
PIN 29 PP5V_S0_GFXIMVP_ VDD 5.1V
Pin 7 PP1V8_S0_GPU -0.00V
PIN 30 PP5V_S0_GFXIMVP_VDD 5.1V



RA012 Pin 2 GPUVCORE_EN 0.000V
R9824 Pin 1 EG_RAIL4_EN -0.000V
 

peeka79

Member
Here is What I?m Getting for those 2 Power Lines...

RA011 Pin2 P1V8GPU_EN -0.000V
CA906 Pin1 REG_SSTR_P1V8GPU 0.000

CA950 Pin1 P3V3GPU_RAMP 0.000V
RA010 Pin2 P3V3_GPU_EN 0.000V
 
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