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820 4924 taking 51 mA and not getting into S4 state

R

Roan

Member
Medusa arrived together with a regular programmer

I've downloaded a full BIOS, made a backup of the current BIOS en flashed the fresh one. I let medusa clean the ME but still no activity on USB or Display.

I think I am also not sure about the Vcore. On this model I measure PPVCC_S0_CPU which looks to be the CPU power in, is this the "Vcore"
 
2informaticos

2informaticos

Administrator
Staff member
Yes, PPVCC_S0_CPU is common power rail for core CPU and iGPU.
Did you verify Mac ROM against Medusa ROM after each read/write operation?


vcore.jpg
 
R

Roan

Member
Yes I verfied it with two BIOSes right now. I can link them but don't know if that's allowed on the forum

Summary until now:
All S0 rails work as does Vcore (very nice and stable 1.85V)
Tried flashing two different bioses all verified and afterwards Cleaned by the Medusa
No USB activity nor any image on macbook-/external display (also tried with flashlight in case of no backlight.
Have the board only connected with the DCIN adapter, no battery nor fan connected (don't know if that makes a difference on that board)

Next up:
Buy a 85W charger to get amperage for further troubleshooting? (only have a 45W snipped hooked on my PS right now and using a fully functioning 60W version which is not snipped.
Check all S0 subrails for voltage and short? ("bruteforce searching" as I don't have any idea what could be the issue right now.)
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
Fan doesn't help to diagnose this board.
It only spins very late, when CPU gets really hot.

Test for USB activity on the onboard port.

This board should start with 60/85W Magsafe 2 charger, but not 45W one.

Didn't find clean ME (tested) BIOS posted on the forum?
 
R

Roan

Member
Tested for USB activity on onboard port. My normal desktop gives a flashing red light.

Used a 60W and 85W charger
Used 4 BIOSes, cleaned all ME's through medusa and verified every step of the way and also checked if Vcore was present.
One of those 4 bioses was the only 820 4924 bios I could find on the forum which did not have an expired link. Sadly I could not find out if the BIOS was for a 820-4924-A or non -A.

Also tested through MiniDP but the only response I got was that the port game power, no display visible.

Am I maybe missing the BIOS SN change? Should I change the SN of the flashed dump to correspond with the old SN?
 
R

Roan

Member
Is there anything else I can check? Maybe the SPI chip not communicating properly? Short on any S0 subrail? Or confirming dead CPU somehow?
 
2informaticos

2informaticos

Administrator
Staff member
Check all SPI Bus Termination resistors and traces.
Not too much else to check.
Could be damaged CPU this case...
 
R

Roan

Member
There was a broken trace between R6118 and R6130. Now it boots but with questionmarkfolder. Does not recognize SSD and does not give bootoptions when holding option key. Making a bootable Catalina drive, will update tomorrow!
 
R

Roan

Member
OS on external HDD gives me this. First boots normally, but around a half filled loading bar it starts behaving like this and reboots after ~30 sec
 

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R

Roan

Member
Used your BIOS and cleaned ME afterwards. Verified and all. After starting the ME changed which means the PCH has turned on. I can see some indication of waterdamage near the BIOS connector leading under the RAM heatshield. Any way to remove that thing? Since 500 celsius and 120L/min wont do.
 
R

Roan

Member
Wont start any MacOS recovery. Can choose wifi, but the loading bar after that does not got further than halfway.
 
R

Roan

Member
It finally worked! Took a while since I waited for a tool to make a backup of the SSD. Put Catalina on a pendrive and let it restore the os.

Thanks slot!

One last question. Why doesnt the online recovery method work (while giving weird screen distortions) when the pendrive way does work?
 
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