Chosen Solution
I’m in the process of replacing the LCD on an iPhone 8. In the past (on older models), I’ve always tested the LCD prior to transferring all of the LCD assembly components. However, when I connect the LCD ribbon cables and power up the phone it only displays the Apple logo. If I disconnect the battery and reattach the LCD cables of the OEM screen the phone boots up. What components of the old LCD assembly HAVE to be attached to the new one to test it prior to a full install? Could it be the home button assembly not being installed or something not being grounded or any essential screws?
You are right, you need at least a home button plugged to LCD for phone to boot up normally. If this is going to be your first screen replacement on a 8 phone, please be careful of the front camera assembly especially where the proximity sensor and ambient light sensor is. Their next to each other and are held in snug with plastic gasket (one piece to hold both) and a bit of glue. I recommend heating them up well (80°C for like 5-10 seconds) to weaken / loosen the glue and adhesive.
