2 No power, diagnostic results, power supply, logic board, or DC cable?
I’ve looked through the entire forum, but haven’t found anyone who posted their diagnostic results with any answers. I’m running in circles at this point.
I’m trying to determine if it is the logic board, power supply, or DC power cable from PSU to Logic. System does not power on at all.
State 1:
LED #1 comes on - which means standby power is present.
Pin 1 & 4 - has 12v
Pin 1 & 11 - has 12v
Pin 1 & 12 - has 0v
If I hold the power button on for 3 seconds:
State 2:
LED #2 however, never comes up or blinks during this whole process.
Pin 1 & 4 - has 12v
Pin 1 & 11 - Volt will just down to 3v then 1v and slowly decrease and rest at 0v
Pin 1 & 12 - Will have 4.59v
If I press the power button once it will immediately go back to “State 1”
All this started happening immediately after I installed an update for Sierra, the system would randomly turn off, it happened about 3 times and then it will turn back on by itself after a minute or 2. But after it happened for the third time, it no longer turned back on. I’ve done all the disconnect power cable, reset SMC, tried another outlet, etc. I’ve also pulled out all the RAM.
**4/16/19** Update
Swapped power supply with another working iMac same exact model. The other iMac worked which means the original power supply works. The iMac with problem still does not turn on with another power supply. Reacts the same way as mentioned above.
Bu iyi bir soru mu?
1,1b 
2,6b 
2 Yorum
Heating? Can you please explain you mean by heating?
Win tarafından
At this point I think you've proven the issue is within the logic board.
There are additional power regulators on the logic board I'm suspecting you damaged them.
This is a common issue when the system gets a power line hit. Really need a good surge suppressor or better yet a UPS! The other risk is the peripheral devices also need protection as a lighting hit could enter through the other ports as well (USB, FireWire, DisplayPort or Ethernet)
Dan tarafından