820-00850 power on problem

Kyle93

Active member
Arrived not powering on and no liquid damage with CPU getting warm. While plugged in if buttons are pressed like you are trying to enter DFU mode the apple logo appears and the machine boots successfully. At first it will seem fixed, you can shut down and press power button within a few minutes and boots up no problem. Battery checked and in good health.

However if machine is left sitting for a bit the same problem returns. Does this sound like a T2 problem?

Port needed to try a DFU restore currently is not working. usb amp meter does not even light up on this port, What needs to be checked first to solve that issue?
 

Kyle93

Active member
PP1V8_UPC_XA_LDOD 0.035

PP3V3_UPC_XA_LDO 0.016

Found U3100 was faulty from these readings, replaced and now all the ports are working again however machine is still having a power on problem.

Revived T2 in DFU mode which makes the machine boot up after it finishes installing however after the machine is turned off for a few minutes the same issue returns. CPU warm but not powering on.

Would it best to backup users data and restore T2 chip instead of the revive option?

If not what else should be checked??
 

Kyle93

Active member
Tried restore and finished successfully however same problem is still occurring. What should be tried next?
 
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Kyle93

Active member
Yes. After user account was created shut it down. Turn it back on immediately powers on no problem. Shut it down wait 45 minutes same problem returns. Nothing happens when pressing power button. Can only get it to turn on again after sitting 45 minutes or more by holding keys down as if going into DFU. Other macbook not plugged in when it turns back on from holding DFU keys
 

Kyle93

Active member
Turns on consistently during and after performing a SMC reset. During the first ten minutes of shut down after the reset it will power back on immediately whether you press only the power button, right shift key or left option or left control. Any of these keys can be pressed individually and it will power on however if it sits powered off more then minutes you have to hold all the keys again including power button.

Can SMC be faulty or something else??
 

Kyle93

Active member
Measured in wrong area. PPVCCEDRAM_S0_REG_R is 1.1V however PPVCCT_S0_CPU is 0V throughout the whole process with only a/c adapter battery unplugged.

draws 20v at exactly 0.33a and stays there. At first fans spin a couple seconds then turn off then about a minute later the fans start to spin but gradually increase in speed.
 
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Kyle93

Active member
What is the signal on the board to trip SMC_BYPASS?

On older boards like 820-00165 I know its SMC_ONOFF_L but that term does not come up in boardview on 00850
 
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