SOLVED - 820-4924 dead

[jadao]

PPBUS_G3H: 12.56V PP5V_S5 5V PP3V3_S5: 3.3V PPVRTC_G3H: 3.3V normal green/orange magsafe light
No further power rails present.

U1900 seems ok, I can see 32KHz present, SMC_ONOFF_L, SMC_RESET_L present at 3.3V

Found a very small micro greenish spot near smc, cleaned it and reflowed SMC but nothing changes may need a replacement or reball.

Also, with SMC bypass all rails are present but no chime (CPU voltage is at 1.8V), witch may indicate a sensor or SMC issue.

Anything I could troubleshoot further before replacing SMC?

Thanks!

 

[JohnB8812]

Try a new SMC first

 

[2informaticos]

First of all, be sure to have original 60/85W Magsafe 2 charger.
If liquid signs around SMC, better to rerball it.
Check AVREF_SMC presence.
If OK, post CHGR_A/BMON values.
Also check resistance between pins 17/18 and 27/28 of ISL6259.

 

[jadao]

Thanks JohnB8812 and 2informaticos,
Didn't yet replaced smc.
Always using original 85W magsafe 2 for magsafe2 power jack boards.
Should had mention I've already checked isl6259 pin 17-18 and 27-28 they are normal 25,5V and 5,5V.
AVREF_SMC is present at 3,3V.
CHGR_A/BMON are 0.031V and 0.053V respectively.

 

[2informaticos]

"isl6259 pin 17-18 and 27-28 they are normal 25,5V and 5,5V."
I don't understand what this means...

Post basic signals for power on sequence in normal mode.

 

[jadao]

Sorry I was tired. I mean ohms instead of volts!
Resistance on ISL6259 pins 17/18 is 25,5 ohms and 5,5ohms on pins 27/28.
thanks

 

[2informaticos]

Still waiting for signals.
Do you get 3V3_S5/SUS?

 

[jadao]

Hi, here are all values I noted.

PPDCIN_G3H 16,5V
PP3V42_G3H 3.42V
PPBUS_G3H 12,56V
PPVRTC_G3H 3.3V

PP5V_S5 5V
PM_SLP_S5_L is missing (0V) so S4, S3 and S0 versions of PP5V are 0V

PP3V3_S5 3.3V
PP3V3_SUS 3.3V

PP3V3_S4 0,446V
S4_PWR_EN is missing (0V) because of PM_SLP_S5 missing


PP3V3_S3 0,23V
=P3V3S3_EN is missing (0V) because of PM_SLP_S4_L missing

PP3V3_S0 2.02V (0,293 diode mode)

32KHz present at u1900

SMC_ONOFF_L 3.3V
SMC_RESET_L 3.3V
S5_PWRGD 3.4v
SMC_ADAPTER_EN 3.4V
PM_BATLOW_L 0.19V
PM_PWRBTN_L 3.4V
PM_SYSRST_L 2.09V

PCH_SRTCRST_L 3.3V
PCH_INTRUDER_L 3.058V
PCH_INTVRMEN 3.237V
RTC_RESET_L 3.328V

As I said earlier SMC bypass makes board to turn on with fan running high (no chime)
I see that PM_BATLOW value is not normal... Also the presence of 2.02V on PP3V3_S0.

Thanks!

 

[2informaticos]

See what happens without U8030.
Do you get any S3 voltage in normal mode in such case?

Check SMC_DCIN_VSENSE level.
Low PM_BATLOW_L blocks PCH to start.
If you have correct charger for sure, then could be SMC issue; change it, for test.

 

[jadao]

Without U8030 I had no S3 voltage.
SMC_DCIN_VSENSE voltage is 2,42V whitch looks ok according to the voltage divider.

Changed SMC and yes the board is back to life!

I am sure just a reball would have worked but I didn't bother, board is in immaculate condition with white indicators but still this little corrosion I saw was the only hint.
Thank you very much for your support.