820-3437 pm_slp_s4 0.86v

[2andrewd]

Hey guys, looking for a hint or two on how or whether or not to even proceed with this one. Thanks in advance!


No LD visible upon receipt.

D7012 was knocked off. replaced and restored pp3v42_g3h green/orange light.

Began checking rails and of course everything is present up to PP5V_S4_RS3 whose enable signal at pin 4 of u7501 is sitting at .86v which is what pm_slp_s4_l is reading "up stream" and across the board. checked p/u resistors and any along the path of pm_slp_s4_l, they are within spec. What sort of scenario's could cause this odd reading?

PM_SLP_s4_L .86v stable (is this a pch middle finger held high?)


PPBUS_G3H 8.6
PPBUS_S5_HS_COMPUTING_ISN 8.6
PPBUS_S5_HS_OTHER_ISNS 8.6
PP3V42_G3H 3.45
PPVRTC_G3H 3.3
PP5V_S5 5

pp3v3_S5 3.3

 

[dukefawks]

Check the usual U1900/50, U6100 including traces and termination resistors to data lines, JTAG connector.

 

[2andrewd]

R6114 was missing. U1900 showed signs of someone else's work and looked untrustworthy so i replaced it along with y1905. I couldn't find the exact clock chip on any donors but plenty with the same prefix which I assumed to be acceptable substitute? termination traces beep.

Looking through the pch power management inputs that appear to be required for pm_slp_s4_l I found...

PM_PWRBTN_L never comes higher than 1.05v. P/U's and other res's on the line are within spec.

 

[dukefawks]

PM_PWRBTN_L should be high of course. Probably crap under SMC if the pull up resistor on this line is ok and has 3V on it.

 

[2andrewd]

Hey hey,

Finally got back to this one. Pulled and re balled the smc, same behavior as stated above unfortunately. What are possible causes for pm_slp_$4_l to read 0.8v? I read a reply that Louis posted on a similar situation (1v) where he stated that 1v is not a "valid" reading. Essentially should be all or nothing is what I interpreted?

pm_pwrbtn_1 is still hanging at 1.05v.


Thanks in advance for any input you guys might have.

 

[dukefawks]

PM_PWRBTN_L hanging at 1V would certainly cause this board to never power on. Check the pull up resistor R1405 and voltage there. If there is 3V there and R1405 is ok then it is either a dead SMC or a dead CPU.
Rip out R1802 to make sure the pull down is not coming from there.

 

[2andrewd]

Thanks for the clues. Followed your leads and I'm ashamed to reply that this is one is a clear-cut case of CPUicide.

Lastly... Are brown/motley-crue-looking-inductors indicative of anything or is that an eventual normal life cycle presence & presentation?

 

[dukefawks]

No idea, I would need to see it.

 

[2andrewd]

No Title

Something such as .....

 

[dukefawks]

I see nothing wrong.

 

[2andrewd]

Thanks for that.

I have nothing further for this thread, looks like a "solved" fail candidate.