820-3437 pp3v3_s4 missing.

No-Clean

Member
Clean board, came in with a low ppbus, all was good so I replaced the SMC and board worked again for about 1 day, not it is not turning on anymore, ppbus is good at 8.59v but pp3v3_s4 is 0.34v and about the same with PP3V3_S3 but they are not shorted.

Any pointers will be greatly appreciated.
 

2informaticos

Administrator
Staff member
Do you get 3V3_S5/SUS?
SMC_RESET_L OK, amber light on Magsafe present?

Try the MLB alone, disconnecting LIO flex.
Also try to start in SMC bypass mode.
Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L at same time.
 

No-Clean

Member
PP3V3_SUS is 0v
SMC_RESET_L is fine at 3.3v
amber light yes
no flex same problem
I do get a pulse on PM_PWRBTN_L when I trigger SMC_ONOFF_L
SMC bypass Mac wont start either, can you please explain why this is relevant? I have tried this on a lot of boards and almost all of them start up in SMC bypass.
 

No-Clean

Member
PM_BATLOW_L 3.3v
S5_PWRGD 3.3v
PM_DSW_PWRGD 3.4v
PCH_INTVRMEN 3.2v

Not sure about RTC signals but here is what I think it is:
PPVRTC_G3H 3.3v
PCH_CLK32K_RTCX1 0.4v
 

2informaticos

Administrator
Staff member
I expected 4 RTC signals, RTC_RESET_L, PCH_SRTCRST_L, PCH_INTRUDER_L; PCH_INTVRMEN_L already posted.
Also post PCH_DSWVRMEN.
 

No-Clean

Member
Thanks, here they are

RTC_RESET_L 3.3v
PCH_SRTCRST_L 3.3v
PCH_INTRUDER_L 3v
PCH_INTVRMEN_L 3.2v
PCH_DSWVRMEN 3.2v
 

2informaticos

Administrator
Staff member
"I do get a pulse on PM_PWRBTN_L when I trigger SMC_ONOFF_L"
Do you mean drop pulse, like 3-0-3?
Check if any PM_SLP_Sx_L signal pulses at same time.

Reball SMC, or change it again.
Be sure to have good solders on it.
 

No-Clean

Member
Too late, Im already replacing 2nd SMC since the first one I tried this morning is doing the same, with this I will for sure know that this SMC are good or not.
 

No-Clean

Member
Ok with known good SMC
PM_SLP_S0_L is 0.053v and does not pulse when I trigger
SMC_ONOFF_L
PM_SLP_S3_L is 0v no pulse
PM_SLP_S4_L is 0v no pulse
 

No-Clean

Member
Thanks, I have never tried this, should I do it with BGA machine or hot Air? If BGA machine any recommendation on profile?
 

No-Clean

Member
I was cleaning the corners of the CPU to remove the clear paste and after that I tested the board and it is working, I cleaned the corners at 250c with 70 air on a Quick 861DW, but for some reason I don't think this will last, any tips on how to do this right will be greatly appreciated.
 

2informaticos

Administrator
Staff member
You only need quality flux and heat PCH/CPU at 180-200 degrees, to burn the crap between balls.
No need to melt the balls; hot air station is good enough.
 

No-Clean

Member
Thanks a lot, after the reflow still works, will give back to customer and see.

This post has a lot of great info, I will save it and make notes for future reference.
 
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