TLDR: system would boot but no chime, no screen, only fan spinning up to high speed after 1-2 minutes. Isolated logic board showed expected voltages except ADAPTER_SENSE (0V and unexpected OPEN LINE to Ground when unpowered). Problem resolved after several minutes of rest. Should I consider replacing a chip that's on its way to failing?
DETAILS
I'm working on the same system mentioned in this post. After about a week running stable, I eventually removed the drive (SATA SSD) to scan for issues and do a fresh OS install. **Possible mistake during reassembly - see below** Upon boot up, the system chimed but no screen activity and fan went from normal to fast after 1-2 minutes. I forced a shutdown to not risk thermal damage. Waited and retried - no chime, no screen, fan went from normal to fast after 1-2 minutes. Tried to reset NVRAM and SMC; no indication of success, no chime, no screen, fan went normal then fast after a minute or so. Removed the logic board, checked voltages and resistance...
**Possible mistake**
During disassembly, I noticed a piece of thin metal from the display cable retainer (pictured) was lose laying between the frame and logic board near R6929.
(from rough memory)
PP3V42_G3H ~3.5V
PP3V3_S0 ~3.5V
SMC_BC_ACOK ~3.5V
Unexpected find => ADAPTER_SENSE (@J6900, R6900, U6900) 0V and test to ground shows OPEN LINE
After a while of checking voltages and resistance with nothing else out of the ordinary (limited in my knowledge), I took a break, came back and ADAPTER_SENSE is now showing 40k resistance. Reassembled system, boots as if nothing ever happened.
Is this the sign of a chip starting to fail? Anything I should try or check?
DETAILS
I'm working on the same system mentioned in this post. After about a week running stable, I eventually removed the drive (SATA SSD) to scan for issues and do a fresh OS install. **Possible mistake during reassembly - see below** Upon boot up, the system chimed but no screen activity and fan went from normal to fast after 1-2 minutes. I forced a shutdown to not risk thermal damage. Waited and retried - no chime, no screen, fan went from normal to fast after 1-2 minutes. Tried to reset NVRAM and SMC; no indication of success, no chime, no screen, fan went normal then fast after a minute or so. Removed the logic board, checked voltages and resistance...
**Possible mistake**
During disassembly, I noticed a piece of thin metal from the display cable retainer (pictured) was lose laying between the frame and logic board near R6929.
(from rough memory)
PP3V42_G3H ~3.5V
PP3V3_S0 ~3.5V
SMC_BC_ACOK ~3.5V
Unexpected find => ADAPTER_SENSE (@J6900, R6900, U6900) 0V and test to ground shows OPEN LINE
After a while of checking voltages and resistance with nothing else out of the ordinary (limited in my knowledge), I took a break, came back and ADAPTER_SENSE is now showing 40k resistance. Reassembled system, boots as if nothing ever happened.
Is this the sign of a chip starting to fail? Anything I should try or check?
