When troubleshooting a board issue on a 2 layer sandwich board, sometimes it's a good idea to isolate the board to the bare minimum.
Example of an iPhone 15 sandwich board separated into its 2 layers
That includes, splitting the sandwich & test with the top board only.
When in doubt, test the top board with a known good bottom board in a socket jig tool, like a Qianli iSocket.
Below is a list of each sandwich model & what happens when you test with top board only
Top Board Only Sandwich Boards
Will boot?
Touch?
Restart Issues?
Temp Warning Issue?
Notes
iPhone X (Intel)
No
No
N/A
N/A
Top Board Only will boot to DFU Mode. You can flash & retain user data on 3u Tools to get it to boot.
Or you can bypass dfu mode with top board only by running a jumper from pin S41 to S48
Requires Charging Port to prevent top board only from restarting (Mic1)
iPhone X (Qualcomm)
Yes
No
No
No
Must use Socket Jig to get touch working
Requires Charging Port to prevent top board only from restarting (Prs0/Mic1)
iPhone XS, XS Max
Yes
No
No
No
Must use Socket Jig to get touch working
Requires Charging Port to prevent top board only from restarting (Prs0/Mic1)
iPhone 11
Yes
Yes
Yes
No
Since mic 2 connects to the main board via the sandwich, it requires the bottom board to avoid 3 min restarts.
Requires Charging Port to prevent top board only from restarting (Prs0/Mic1)
iPhone 11 Pro, 11 Pro Max
Yes
Yes
No
No
Can get data with top board only. Just make sure to plug in a power button flex (Mic2) and charging port flex (Prs0/Mic1)
iPhone 12, 12 Pro, 12 Mini
Yes
Yes
No
No
Can get data with top board only. Just make sure to plug in a charging port flex (Prs0/Mic1)
If you want brightness to work, plug in the ear speaker flex. If ALS sensor is not detected, screen will stay dim
iPhone 12 Pro Max
Yes
Yes
No
Yes
With top board only, the phone will boot to a false positive overheating temp warning, even if it's cold.
You can bypass the temp warning by running a 10k Ohm resistor to ground on these 2 lines: a. Pin 487 - NTC_RADIO_BB_SE b. Pin 489 - NTC_RADIO_PA_SE
You can also just plug in a known good bottom board using an iSocket jig to get data
Make sure to plug in a charging port flex (Prs0/Mic1) to prevent 3 min restart
If you want brightness to work, plug in the ear speaker flex. If ALS sensor is not detected, screen will stay dim
iPhone 13 Mini
Yes
Yes
Yes
No
This model requires the bottom board to prevent 3 min restart (0x400)
The issue is, the top board must communicate with the gyroscope in order to function correctly and not restart every 3 minutes. Rebuilding pads 207, 208, 502, 503, 504, 527, 528 is all that is needed from the bottom board.
You can also just plug in a known good bottom board using an iSocket jig to get data
Requires proximity flex to prevent board only from restarting (0x1000)
Requires charging port flex to prevent board from restarting (0x800)
iPhone 13, 13 Pro, 13 Pro Max
Yes
Yes
No
No
You can get data with just top board only.
Requires proximity flex to prevent board only from restarting (0x1000)
Requires charging port flex to prevent board from restarting (0x800)
iPhone 14, 14 Plus
No
N/A
N/A
N/A
Requires both layers connected for the board to boot
iPhone 14 Pro, 14 Pro Max
Yes
Yes
Yes
No
This model requires the bottom board to prevent 3 min restart.
Unknown what is needed from the bottom board to prevent the 3 min restart. (0x20000)
You can also just plug in a known good bottom board using an iSocket jig to get data
Requires proximity flex to prevent board only from restarting (0x80000 )
Requires charging port flex to prevent board from restarting (0x40000 )
Requires the power button flex to prevent board from restarting (0x10000)
iPhone 15, 15 Plus
No
N/A
N/A
N/A
Requires both layers connected for the board to boot
