820-3332 - Momentary fan spin

victor

Member
Disabling GPU doesn't remove it from the board.
GPU can still block some data lines of CPU.

If is not GPU, is something which reacted to heat, usually a BGA chip...

Yeah - the heat has definitely changed something c ause it doesn't turn off any more. It just spins up to full speed and then stays like that until i cut the power.
 

2informaticos

Administrator
Staff member
Someone else messed up with this machine before.
Never believe history client when he was involved in the problem of the machine.
Do you think a serious repairman leave the thermal paste spreaded on the board in such way?
 

victor

Member
Yeah... you’re totally right.
Listen - thanks so much for all your help on this, I have learned a lot from you.
 
Last edited:

victor

Member
Dude... I fixed it!!!

Turns out - they had crushed C8431, which has FB_A0_VREFC on it. I cant imagine why this caused the fault symptoms as it wasn't shorted, it was open. Does that make sense to you?
 

victor

Member
Well... It lasted 10 days lol. The laptop has gone back to being totally dead, except the symptoms are consistent now. When turned on, the fans slowly increase in speed until they are at full speed. The laptop then stays in that state, fans at full speed and nothing on screen, no boot chime. No CPU VCore. Is this just a write-off at this stage or do you have any idea what i can check? Must be something intermittent right?
 

2informaticos

Administrator
Staff member
Post which voltages appear on the board.
Did you disable GPU power supply too?
Lift its coils also.
I didn't even check that mod, not sure how they did it.

Any reason to quote an entire post visible few centimeters above?
Please maintain forum aesthetic...
 

victor

Member
Okay, here are current voltages.

PPBUS_G3H - 12.25v
3V42_G3H - 3.42v
PP3V3_S5 - 3.33v
PP3V3_SUS - 3.33v
SMC_RESET_L - 3.38v
PM_BATLOW_L - 3.32v
PM_RSMRST_L- 3.30v
PM_PWRBTN_L - 3.41v
PM_DSW_PWRGD - 3.41v
PCH_DSWVRMEN - 3.21v
PPVRTC_G3H - 3.33v
RTC_RESET_L - 3.32v
SYSCLK_CLK32K_RTC = 0.433v
PPVOUT_G3_PCH_DCPRTC - 1.552v
PM_SLP_S5_L - pulses to 3.33v and down to 0
PM_SLP_S4_L - pulses to ? around 2v and then down to 0
PM_SLP_S3_L - pulses to ? around 3v and then down to 0
PM_SLP_S3_R_L - pulses to ? around 3.2v and then down to 0
L2406 - pulses to 0.8v
L7530 - nothing
L7520 - nothing
L7510 - nothing
L7550 - nothing
L7560 - nothing
L8960 - nothing
L8930 - nothing
L9830 - pulse to 0.5v
L7330 - pulse to 0.5v
L7030 - 12.25v
L7220 - pulse to 4v
P1V8S0_EN - Pulses
P1V8S0_PGOOD - pulses to 3v
PP1V8_S0 - pulses to 1.8v
PP3V3_S5 - solid 3.32v
P1V5S0_PGOOD - pulses to 3.2v
PP5V_S0_P1V5_LDO - pulses to 4.4v
PP1V8_S0_P1V5_LDO - pulses to 1.6v
PP3V3_SUS - solid 3.32v
L7630 - Pulses to 1v
L7720 - pulses to 1.7v
L8310 - nothing
L8360 - nothing
L7770 - pulses to 1.5v
1V05_SUS - 1.062v
PP3V3_S4_FET - pulses to 1.7v
PP3V3_S3_FET - pulses to 3v
PP5V_S3_FET - pulses to 4.6v
PP1V5_S3RS0_FET - pulse to 1.1v
PP3V3_S0GPU_MISC_FET - no pulse, steady at 0.06v (checked for short - no short!)
PP3V3_SUS_FET - 3.32v steady
PP5V_SUS_FET - 5.00v steady
PP3V3_S0_FET - pulses to 3.32v
PP3V3_S0GPU_FET - nothing (checked for short - no short!)
PP5V_S0_FET - pulses to 5v

The mod involves cutting GPU power supply by removing resistors, removing U9150 and running a bunch of jumpers, i have attached a diagram.
 

Attachments

  • 94144473_3724205570985000_4304734854789988352_o (1).jpg
    94144473_3724205570985000_4304734854789988352_o (1).jpg
    244.7 KB · Views: 1

2informaticos

Administrator
Staff member
" PPBUS_G3H - 12.25v "
You have other problem too, not only graphics; if this voltage is on charger only.
No reason to check GPU voltages, if is disabled.

Did you try SMC bypass now?
 

victor

Member
PPBUS_G3H was measuing 12.25v when you told me it was the GPU before...

Yeah I've tried SMC bypass - it starts with all the fans blazing at full speed straight away, rather than building up, but aside from that nothing else happens. It doesn't switch on properly and none of the voltages change.
 

2informaticos

Administrator
Staff member
So board stays on in SMC bypass with the same voltages???
If fans spin at max, 5V_S0 must be steady...

With that PPBUS_G3H, the board will not charge battery.
Consider if is worth to continue with the repair...
 

victor

Member
Well... I'd certainly like to continue with the repair for as long as you are willing to help me with it! But if you think it is time to give up - i will listen.

I am not testing the board with battery, just charger.
Actually yes you are right - 5V_S0 is steady while the fans are spinning.
 

victor

Member
Yes - the pulsing ones are stable now. Occasionally it reverts to quarter fan spin though, which comes with the pulsing again.
 
Top