820-3437 no fan, pulsing

[Palhano]

The board was in good condition, but it wouldn't turn on. PPBus had 8.2v and SMC_RESET_L was low. Replaced the R5100 and the Mac came back. It worked fine for two weeks and stopped.

The font pulses up to 0.160, as do some lines.

RTC_RESET_L - 3.26V
PCH_INTRUDER_L - 3v
PCH_INTVRMEN - 2.5v
PCH_DSWVRMEN - 2.4v
PCH_SRTCRST_L - 3.26V

PPBUS_G3H - 8.6v
PP3V42_G3H - 3.4v
PPVRTC_G3H - 3.3V
PP5V_S5 - 5v (pulsating)
PP3V3_S5 - 3.3V (pulsating)
PP3V3_SUS - 0
SMC_ONOFF_L - 3.37v

SMC_ADAPTER_EN - 0
SMC_PM_G2 _EN - 3.4V

I tried SMC bypass mode, it didn't work. I've already checked the SPI resistors.

I think it could be the SMC, but I don't have a replacement.

any tips?

 

[2informaticos]

Try reballing SMC...

 

[Palhano]

Reballing and it didn't work. I got an SMC chip and replaced it.

I returned to the initial problem. PPBus 8.2v and SMC_RESET_L low. The R5100 is fine, 100k. I have 3.42 on pin 1 and 0.6 on pin 2.

 

[2informaticos]

Be sure no corrosion between J6100 pads.
Remove R7100 and check SMC_RESET_L.
If still low, replace U5110.

 

[Palhano]

I had removed the J6100.

Without the R7100, the SMC_RESET_L remains low, even when replacing the U5110. I put the R7100 back in place and now I have 3v. But PPBus remains 8.2v

SMC_ADAPTER_EN - 0
SMC_PM_G2 _EN - 0

Maybe the SMC chip I got is bad?

 

[2informaticos]

Try another one...

 

[Palhano]

With a "new" SMC, it worked again. Let's go to the tests.

Thank you very much for your help, once again!