820-01700 // Will not startup // U1200 extreme heat

Zeifurhugen

New member
Hi,

I have an 820-01700 that has no visible or accidental damage.

The symptoms were that the MacBook got really hot, shut down and will not turn back on.

I have inspected the board closely and have been unable to find any damage or short circuits. The when attempting to boot the board, it shows 20v in all ports with normal amp draw almost reaching 2.5A. (seems like it is booting). I tested voltages on CPU lines and CPU power supplies and everything appears normal.

T2 Revive completes without any issue but does not fix the no boot issue.

The interesting thing is that the U1200 PCH gets EXTREMELY hot. I replaced U1200 from a 820-01700 donor board and the same exact issue persists, U1200 gets extremely hot. T2 revive still completes without issue, but logic board still does not boot.

The cpu/gpu heat up as well but not even close to as hot as the PCH U1200.

Any idea why the PCH is getting so hot? Seems like it is likely related to the problem in some way. Is this possibly a bad CPU causing it to get super hot?

Any ideas/troubleshooting would be greatly appreciated.

Thank you!
 

Zeifurhugen

New member
PP3V3_S5 - 3.38V
PP1V8_S5 - 1.79V
PP1V05_PRIM - 1.03V
PP1V05_PRIM_PCH_VCCAXTAL_F - 1.03V
PP1V05_PRIM_PCH_VCCAPLL_F - 1.03V
PP1V05_S5_PCH_VCCDSW - 1.03V
PPVCCSPI_PRIM_PCH - 3.33V
PP1V8_S0_PCH_VCCHDA_F - 1.79V
PP3V0_G3H_RTC - 3.0V
PPDCPRTC_PCH - 1.51V
PP1V24_S5_PCH_VCCDPHY - Dropping from 0.8V
PP1V8_PCH_VCCPHYLDO - 1.87V
PP1V_PRIM_PCH_VCCAMPHYPLL_F - 1.03V then starts jumping around (always below 1.03V)

I think I tested all rails on those 2 pages.

I appreciate your help, thanks.
 

2informaticos

Administrator
Staff member
If no important data, then try restore option into DFU.

Do you note any changes on L7211 voltage, in the first 10-15s?
Check for USB activity.
 

Zeifurhugen

New member
L7211 is very stable at .95V

Unfortunately I can't restore the T2 as the data is very important.

Apologies, but when you say check for USB activity, what do you mean?

Thanks :)
 

2informaticos

Administrator
Staff member
Can you access its SSD in Target Disk mode?

"when you say check for USB activity, what do you mean?·
Read more here.
 
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