Hello,
I've got here 820-3787 that turns on to a questionmark folder with known good drives (with High Sierra installed and running on different machine). It will also not find any wifi network in boot selection menu. USB is fully functional.
I bought this machine with no video issue, but that was just L8300 killed by bad LVDS cable - after changing those two things, it worked well. However the screen was in bad shape, so I ordered a new one. After changing the screen it stopped booting from SSD (just questionmark folder, even with known good drives), so I tried to do an internet recovery, but that immediately gave me 1005F error (even after PRAM/SMC reset), so the wifi also doesn't work. I think it's a PCIe issue, probably caused by bad camera in that new screen assembly. However I also changed SSD at once with the screen and the resistance measurements on camera connector are the same as on known working one, so I'm not certain what caused this issue and if the camera is really defective. The board looks pristine, no spills, oxidation, missing parts, signs of previous repairs or anything like that. I only found a little solder ball next to U3711, so I changed it just to be sure, but that did not solve anything. I also changed U1900, no progress.
I've got here another A1398 with 820-3787 that is fully working, so I can compare my measurements.
All the rails are present and stable, including these:
PP1V8_CAM
PP1V35_CAM
PP1V2_CAM
PP3V3_S3RS0_CAMERA
PP3V3_WLAN
PP3V3_S0SW_SSD_FLT
CAM_PCIE_RESET_L
TBT_PCIE_RESET_L
AP_CLKREQ_Q_L
SSD_CLKREQ_L
CAM_CLKREQ_L is low, but that should appear after successful boot to OS according to the other machine (?)
These components are not shorted and looks pristine:
CAM
C4030 - C4033
C4061
C4062
AP
L3501
SSD
C3710 - C3717
TBT
C2800 - C2807
C2840 - C2847
I've already seen this issue on different 3787/3662, but there was always some bad cap... on this one I don't know what else to look for
Thank you
I've got here 820-3787 that turns on to a questionmark folder with known good drives (with High Sierra installed and running on different machine). It will also not find any wifi network in boot selection menu. USB is fully functional.
I bought this machine with no video issue, but that was just L8300 killed by bad LVDS cable - after changing those two things, it worked well. However the screen was in bad shape, so I ordered a new one. After changing the screen it stopped booting from SSD (just questionmark folder, even with known good drives), so I tried to do an internet recovery, but that immediately gave me 1005F error (even after PRAM/SMC reset), so the wifi also doesn't work. I think it's a PCIe issue, probably caused by bad camera in that new screen assembly. However I also changed SSD at once with the screen and the resistance measurements on camera connector are the same as on known working one, so I'm not certain what caused this issue and if the camera is really defective. The board looks pristine, no spills, oxidation, missing parts, signs of previous repairs or anything like that. I only found a little solder ball next to U3711, so I changed it just to be sure, but that did not solve anything. I also changed U1900, no progress.
I've got here another A1398 with 820-3787 that is fully working, so I can compare my measurements.
All the rails are present and stable, including these:
PP1V8_CAM
PP1V35_CAM
PP1V2_CAM
PP3V3_S3RS0_CAMERA
PP3V3_WLAN
PP3V3_S0SW_SSD_FLT
CAM_PCIE_RESET_L
TBT_PCIE_RESET_L
AP_CLKREQ_Q_L
SSD_CLKREQ_L
CAM_CLKREQ_L is low, but that should appear after successful boot to OS according to the other machine (?)
These components are not shorted and looks pristine:
CAM
C4030 - C4033
C4061
C4062
AP
L3501
SSD
C3710 - C3717
TBT
C2800 - C2807
C2840 - C2847
I've already seen this issue on different 3787/3662, but there was always some bad cap... on this one I don't know what else to look for
Thank you