820-4924 power cycling

[LetsFix]

Hello. So, i got this machine not turning on. there is green light on charger that goes orange, and it responds to a smc reset. i got the board out of the case, and i saw u6100 with corrosion in pin 8. i took it out, and remove c6100 and c6101. i try to reprogram u6100 but its shorted. then i take another u6100 put a proper rom, and put it in the board again. pin 8 of u6100 was blown out, so i run a wire to c6100 pin 1.alright, after this whenever i plug power, it powers once and shut down, i notice this because i conected a usb mouse and i see it lights up once. then i took measurements of sm_slp_s4_p and it was coming up and going down at once. ive already replaced U6101, U1900, and U1950 and still the same issue.

in the forum it says that it wont turn on without battery, and the battery was screwed; so i put one from a 2013 machine that i had lying around. should i get one from a 2015 machine; or this one does just fine?

and
So where do i go from this?.

 

[2informaticos]

The board should start by itself with charger only.
Bu sure to use original 60/85W Magsafe 2 charger.
Also check traces and all SPI Bus Series Termination resistors; there are more than 20...

Where did you get new BIOS?
I think we already have some link posted on the forum...

 

[LetsFix]

with charger only the board acts like its dead, there is no pulsing on charger only. Im using a ORIGINAL 85W magsafe2 charger. ill check the traces later. the BIOS, i got it from a ramdom post at ghostlyhacks, i took it and cleared the ME region. if you have one that you are sure that works, and share it with me i would highly apreciate it.

 

[JohnB8812]

This one will boot without the battery if the charger is OEM. 2013 battery will not work in 2015 so do not use 2013 battery. Post PM_BATLOW_L voltage with the charger only and check all that 2informaticos suggested

 

[LetsFix]

PM_BATLOW_L is 3.3v. The SPI traces and resistors are fine!

 

[2informaticos]

Did you try to start in SMC bypass mode?

Keep the battery out for the moment.
Do you get 3V3_S5/SUS?
Post PM_RSMRST_L, PM_PWRBTN_L, PCH_DSWVRMEN, PM_DSW_PWRGD.
Trigger SMC_ONOFF_L and check for reaction (drop pulse) at PM_PWRBTN_L.
If yes, chek for pulse at PM_SLP_Sx_L signals at same time.

 

[LetsFix]

Dunno how to start SMC Bypass Mode.

i have PP3V3_S5 and PP3V3_SUS, steady 3.3V on both.

PM_RSMRST_L =3V

PM_PWRBTN_L= 3.3V

PCH_DSWVRMEN= 2.4V

PM_DSW_PWRGD= 3.3V

What do you mean with ''trigger", i dont get it sorry.

 

[LetsFix]

well, i figure out about the SMC Bypass Mode and the ''trigger''.

When trying SMC Bypass it does nothing at all.

when i trigger SMC_ONOFF_L, PM_PWRBTN_L drops for instant; and the mouse blinks once...moreover PM_SLP_S5_L , PM_SLP_S4_L , PM_SLP_S3_L and PM_SLP_S0_L goes high when i trigger SOMC_ONOFF_L.

 

[2informaticos]

OK, then all S3/0 voltages should pulse too; check if any not.
Also check for pulse at pin 7 & 3 of U1950.

 

[LetsFix]

All S3/S0 rails pulse when i trigger SMC_ONOFF_L.

there is a pulse in pin 7 and 3 of U1950.

 

[2informaticos]

Do you get pulse at VCORE too?

I always recommend to reball SMC on corroded boards.

Also try another BIOS; search the forum...

 

[LetsFix]

I?ve tried two other bios already and nothing. i dont get anything at PPVCC_S0_CPU. Do i reball SMC now or where else do i check?

 

[LetsFix]

Since i have no PPVCC_SO_CPU, i inspected U7310 and U7320. and well it seems the rail of CPUVR_PHASE1 and CPUVR_PHASE2 are shorted to ground...i measure there 0 in diode mode. i have another board here and i measure 50 there!. should i replace U7310 and U7320 only, or should i replace the four mosfets too??

 

[2informaticos]

I bet all the CPU MOSFETs are good.
Lift the CPU coils; if the short remains on the CPU side, then is dead.
Less than 0.1% still possible to be C1031, not CPU...

 

[LetsFix]

Well, it seems its dead then, i dont have the will or the equipment to replace the CPU. the short its in CPUside. anyway, just wondering but can I test the display in a 15 inch machine?. since its dead, i was wondering how to test it...i have one macbook pro 2015 15 inch and i was wondering if the 13 inch display could be tested there...

 

[LetsFix]

Does anybody knows if the 13'' will work on a 15'' of the same year?, i wanna know to see if i can teset the display...

 

[JohnB8812]

For screens yes