[SOLVED]820-4924 - no power

[Alan.L]

someone has worked on this board before me.

board gets green then orange light with an original 85w charger. No fan spin

ppbus_g3h = 12.58
PPBUS S5 HS COMPUTING = 12.57
PPDCIN_G3H = 16.50
PP3V42 G3H = 3.428
PPVRTC_G3H = 3.3-3.4v pulsing
PM_SLP_S4_L = 0.0-0.060v pulsing
pp5v_s3 = pulsing 0v

PP3v3_S3 = 0 - 0.3v pulsing
PP3v3_S5 = 0 - 3.3v pulsing

PPVCC_S0_CPU = 13.8ohm resistance to ground


U1900 looks good but I've replaced this anyway.
U1950 looks good.
Smc looks good, glue is still there.

 

[2informaticos]

ALL_SYS_PWRGD pulses too?

Is better to use o-scope to see if power rails and signals rise theyr nominal values.
A DC voltmeter is too "lazy" to capture very short pulses; eventualy shows smaller values than expected...

 

[Alan.L]

ALL_SYS_PWRGD pulses too?

Is better to use o-scope to see if power rails and signals rise theyr nominal values.
A DC voltmeter is too "lazy" to capture very short pulses; eventualy shows smaller values than expected...

no power on ALL_SYS_PWRGD nor on PP1v8S3.


ALL_SYS_PWRGD show nothing on o-scope.

 

[2informaticos]

Means P1V8S3_PGOOD is missing.
That's the reason ALL_SYS_PWRGD stays low.
Repair corresponding 1V8 power supply.
Check for short first...

 

[Alan.L]

board is fixed. C7518 was missing. previous repairman didn't put that back in

 

[Alan.L]

thanks 2informaticos, you lead me to PP3v3_S5 power supply.