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820-4924 A1502 2015 PP5V_S3 PM_SLP_S4 missing

J

jadao

Member
Got this board and hesitated to repair it as they are becoming cheap. Opened the case and found a big burned spot on magsafe board and DCin circuit, no liquid at all.
I restored all dc-in circuit: F7005, D7010, R7121/R7120 (sensing), R7105. U7190 was replaced also because I got 4.6V on L7195 (P5V1_BIAS).

The board worked once for a while and now it just chimes and power off. Therefore I notice PPVCORE coming briefly to 1.8V and it goes back to 0V.
PM_SLP_S4_L also is high 3.3V briefly and goes to 0.
when it shuts down, PP5V_S3 is missing, I checked all rails/signals required for PM_SLP_S4_L and they are all present:
PPVRTC_G3H RTC_RESET_L PCH_SRTCRST_L PCH_INTVRMEN_L PCH_DSWVRMEN_L PP3V3_S5 PM_DSW_PWRGD PP3V3_SUS PM_BATLOW_L PM_RSMRST_L PM_PWRBTN_L

Anything else I should have checked in my diag?
Thanks in advance
 
J

jadao

Member
I edited the message but somehow it didn't registered, I tried the bypass and it does exactly the same, I mean it will spin the fan full a brief instant and then shuts off.
When I short SMC_ONOFF_L, PM_PWRBTN shifts from 3.3 to 0.3 and it comes back to 3.3V when I release the short on SMC_ONOFF_L.
Changed also the bios but same thing.

Something very odd I would like to mention:
-I am able to boot the board and see the mouse on when I short smc_onoff with board on the table.
-As soon as I plug stuff on it (LCD ssd keyboard ans so on) it doesn't boot anymore when shorting SMC_ONOFF_L even with other topcase/LCD.
-While board boot after shorting SMC_ONOFF_L, as soon as I power it off PP5V_S3 disappear. Only way to power it on again is to short again SMC_ONOFF_L

With charger only cpu_vcore appears a brief moment and shuts down.
Is it reasonnable to try replacing SMC? Or most likely dead cpu?
 
2informaticos

2informaticos

Administrator
Staff member
If battery is not connected, should automatically start when charger is plugged in.

Connect devices one by one and see when the behvior changes.
 
J

jadao

Member
I finally have hopefully more accurate observations.
With board on the table and only mouse and charger plugged in
It will start only if i short SMC_ONOFF_L and it will last around 14 seconds before it shuts off.

With board on the table and mouse and charger plugged in + any components (one at a time) SSD, display port cable or keyboard, it will not start if i short SMC_ONOFF_L, i will just see PP5V_S3 briefly.

In any cases it will never starts automatically with battery disconnected and just charger plugged in.
 
2informaticos

2informaticos

Administrator
Staff member
Be aware, this board requires 60/85W charger!
It will not start without battery connected, with 45W charger.

Do you get image in the 14s when it starts?
 
J

jadao

Member
Yes always working with original 85w magsafe 2 charger.

I see the hdmi active signal ls coming on the monitor and then it goes away when board shuts off. This corresponds with the moment where the board chimes and shuts off I don’t see apple logo.

This board got probably a bad overvoltage from a non original charger, but I don’t see how far a dcin issue can extend in the board circuitry.
 
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