820-4924-A no PP3v3_S4

Have a board in thats been dry-cleaned (see my post in the business forum), but there's no visible damage to the board: looks absolutely clean.
Have all normal readings on rails below PP3V3_S4, but PP3v3_S4 is missing (0V). Cannot find any trace of corrosion anywhere.

Has a green and then orange light on the magsafeboard, but doesnt power on (i know that the fan spins only at higher cpu-temps)
Have tested with knowngood battery.

PP5V_S5 = 4.97V

measured P5VS4_EN on pin 2 of U8060, but get 0V

I don't fully understand how PP3V3_S4 is created.

any pointers?
 

JohnB8812

New member
If P5VS4_EN is missing the PM_SLP_S4_L is missing, and this is gonna suck. Check traces to the SPI ROM and the SPI ROM termination resistors. Check clock voltage make sure it's 3.3 steady. Check U1950 pin 8.
 
thanks for the quick reply. i seem to be getting the shitty repairs lately.. for completeness' sake, here are the measured rails:
PP3V42_G3H 3.41V
PPBUS_G3H 12.51V
PPDCIN_G3H 18.43V
PPVRTC_G3H 3.31V
PPBUS_S5_HS_OTHER5V 12.51V
PPBUS_S5_HS_OTHER3V3 12.51V

PPBUS_S4_X239 0.0V (SPIKES a tiny amount to 0.04V when powersupply is started, but my multimeter is slow)

PP5V_S5 4.97V​


U1950 pin 8 = 3.40V
all traces around U6100 are pristine and resistors look brand new. any specific ones i need to measure?
clock voltage at pin 1 of U1900 & pin 1 of C1910 is a steady 3.31V
 

dukefawks

Administrator
It could be pretty much anything. The usual suspects would be corrosion under U1950/U1900. Corroded traces and/or resistors going to U6100 "termination resistors". Could be crap under SMC too. HiRes picture of those areas may also help for diagnosis.
 
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