820-00597-A iMac 21,5" 2017 random restarts, problem with booting to OS

Narek

Member
More than one week ago my customer brought in an iMac 21,5" 2017 for SSD upgrade. I've replaced HDD, cloned all data to new SSD and put everything back together, standard procedure. After few days customer informed me, that computer restarts randomly and then has problem to turn on showing weird loading screen. As system report says there were two errors, one about power button beeing pressed, second is CPU panic. In my service it sometimes turns on and works stable even for whole day, but if I will turn it off, most likely it won't turn on showing half progress bar screen (left or right side is completly empty, only backlight). I already have changed SSD with other one and replaced RAM modules - no changes. What can it be? Bad BIOS? I was searching for BIOS for this board, but I haven't found any trustful source.
 

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2informaticos

Administrator
Staff member
Disconnect internal LCD and test it with external monitor only.
You can also disconnect power button and use J5120 pads instead.
 

Narek

Member
No changes, it shuts down randomly showing "this computer restarted because of a problem", then loads OS halfway and stucks.
 

Narek

Member
Ok, I will. If what, do you have known good BIOS for this board? Or if I will send you my BIOS file, will you be able to clean ME?
 

2informaticos

Administrator
Staff member
Sorry, I've got confused with other thread; no BIOS for this machine in my library.
I will try to clean your backup later.
 

Narek

Member
I haven't tried BIOS files sent by you because after few days of waiting in the queue iMac doesn't turn on at all. It was untouched, I have turned it off last time, took out power cable and disconneced screen.. today it only has one diode light up on and doesnt react to power button, even if I short power on pins..
 
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2informaticos

Administrator
Staff member
SMC_PM_G2_EN must get high before even.
You should check for reaction at PM_PWRBTN_L and all PM_SLP_Sx_L signals.
Be sure PM_RSMRST_L goes high.
 
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