820-3662-A no Brain

[LCDR2]

Hi

Computer turns on, no chime, keyboard light or video.

Tested CPU power coils 0v.

ALl SYS PWRGD 3.5v
PP3V3 S0 us 3.5v however I get no voltage at 2 of R1950 - should I replace this resistor? (CPUVR PGOOD)

Cheers

James

 

[LCDR2]

Sorry .. I realize now that there must be power coming from u7200 CPUVR-Pgood so the issue lies elsewhere I think?!

CPUVR_VDD 5v
CPUVR_VIN 12.75v

PP3v3_S0 - 3.5v
PP1v05_S0 -.422v
PP1v5_S0 - 1.508v
PPVTT_SO_DDR 0v

 

[2informaticos]

"PP1v05_S0 -.422v"
1V05_S0 must appear before VCORE.
Check U7600 area, post some basic voltages there.

 

[LCDR2]

U7600 - input voltages missing

PP5V_S0 - 5v
PP5V_S0_P1V05S0_VCC 0v

Am I correct in my reading of the schematic that the supply for "PP5V_S0_P1V05S0_VCC" is PPv5_s0 ?

 

[2informaticos]

R7601 is then burnt.
Replace it, but first check for short at PP5V_S0_P1V05S0_VCC; C7602, or U7600 may be bad.

 

[LCDR2]

We replaced R7601 and now have 5v at pin 13

PP1V05_S0 has 300mv.

ppvin_s5_hs_computing_isns 12V

P1VO5S0_DRVH - 300mv
..................... DRVL 0v.
.......................... LL 300mv
..................... . VBST 5v
P1v05S0_Boot_RC drops to 300mv after C7630

P1V05s0_EN 5v

Replaced C7630 no change of voltage at pin2.


U7600 Pin Output
FSEL - .5v
RTN - 0.2mv
OCSET - 300mv
VO - 400mv
SREF - 0v
FB - 300mv
EN - 3.3V

vcc -


-- Checked We replaced R7601 again and now 0v.. has it burnt out again.. or a different issue?

 

[2informaticos]

Why did you replace R7601 again?
You've already got 5V at pin 13 after replaced it first time.

Change U7600...

 

[LCDR2]

Hi

Sorry for the long delay. I have been in hospital having my appendix removed.

I replaced U7600, however before i had time to properly check all the output pins etc I must have shorted something because I smelt the bad smoke and now the laptop won't turn on. Looks like it's back to the drawing board on this job.

 

[2informaticos]

We need some basic signals and voltages for power on sequence.
Check for short all power rails.

 

[LCDR2]

Hi Sorry for the delay in getting back to you. I put this one on the back burner.

33ma draw
PPBUS_G3H - 57mc (diode mode to ground shows 001)
PPVIN S5 HS COMPUTING ISNS - 57.5mv
PPVIN_S5_HS_OTHER3V3_ISNS - 58mv
PPDCIN_G3H - 18.5v
PPDCIN_G3H_ISOL - 18.5v
PP3V42_G3H - 3.43v
PP5V_S5 - 375mv

 

[LCDR2]

I have removed F7140 and F7141. Diode mode to ground on PPBUS_G3H still shows 0. on PPVBAT_G3H_CHGR_REG is approx 300.

Is the next step to inject voltage into PPBUS_G3H and find the warm thing?

Cheers

James

 

[2informaticos]

"Is the next step to inject voltage into PPBUS_G3H and find the warm thing?"
Really NOT!!!

Switch to ohm mode and compare PPBUS_G3H reading with all big coils; check CPU coils in particular.
I bet for a burnt FDMF6808 chip...