Phone Is Non-Responsive After Screen and Charging Assembly Replacement

PHONE: Google Pixel 3 XL 64 Gb

ISSUES:

Screen does not turn on. No vibrations when plugging in or out, or long pressing the power button plugged in or out. No signs of life from a normal user perspective.

BACKGROUND:

Moderate-Advanced electronics knowledge

After living with a cracked screen and bad charging port for the last year, I finally decided to replace them with the parts that I had ordered a year ago to take advantage of winter break.

iFixit Parts in hand (RE-CONFIRMED ORDER: Google Pixel 3 XL Screen, Google Pixel 3 XL Charging Assembly), I went through the following tutorials:

Google Pixel 3 XL Charging Assembly Replacement (Full)

Google Pixel 3 XL Screen Replacement (Step 15-23 - charging asm tut covers 1-14)

Google Pixel 3 XL Back Cover Adhesive Installation

Everything seemed to go, ok-ish. The screen and back removal was a bit of a pain, so I ended up using my hobby heat gun along with the microwave gel pack, suction cups, and picks provided in the standard iFixit phone kit. My gun gets hot, but I never stayed in one spot, always swept across the edge I was prying apart. this took approximately 60 minutes to remove the front and back.

Removed everything, replaced the parts, and re-assembled everything in reverse order after applying screen adhesives (yeah, I know. There was one cord so I figured WTH). The back was lightly assembled, including the fingerprint sensor, and closed it up without back adhesives.

Tried turning it on, and nothing. No screen life, no vibrations, nada.

After 3 repetitions of the same procedure, each time finding something that I thought may have been the cause, I'm still left with a dead phone. It appears that all contacts are engaging, and all wires are hooked up.

I've tried reconnecting the screen but it was destructively removed and is difficult to attach with the new screen connector so close in proximity. The charger was not swapped back to the original either due to the fact that it was charging. I'm attempting to avoid a 4th teardown, but I'll do it if it may be a potential cause.

I'm stuck now, and about to start needing my phone again... and slowly going mad.

BIGGEST LEAD SO FAR:

While playing with toggling the USB power on and off and the battery connector on and off, some sequence of disconnecting connections cause 4 separate instances of vibrations. Two screws were removed on the motherboard shield directly before this was observed. I haven't been able to replicate the vibrations since though, but will continue trying different sequences after posting this.

POTENTIAL ISSUES AND OBSERVATIONS:

1. Draws 0.47A at 5.18V when plugged into my usb amp-voltage meter. Confirmed it was the battery drawing power after first suspecting a short. There could still be a short, but it isn't registering in my non-technical diagnostic methodology.
2. No visible damage or missing SMD components.
3. Heat gun was used on screen and back.
4. Broke the plastic sim card ejection pin in the process. Still works but no longer waterproof.
5. Several push pin parts found in the phone after the first assembly. All now removed.
6. Broke the screen frame by accidently removing it during screen delamination process and was too aggressively cleaning it. Superglued it back together and now seems to work fine. Gapping, but minimal (0.25mm or less).
7. Power may have been reconnected accidently during the first re-assembly.
8. Missed the earpiece gasket the first time

1. Missed that the USB port has a plastic bracket above it that needs to be reused the first time.
2. Missed one screw near on the charging assembly the first time.
3. Missed the button array connector the first time and assembled it behind the motherboard unconnected the first time.
4. leftover rubber gasket parts from the screen kit. Did not find anything on these parts in the tutorials and I'm not sure what they are for. Guessing they were used for packaging. Don't see the relevance given the issues either.
5. Never applied the back adhesives, but I did fray out all contacts and press the phone together when attempting to turn on.
6. Non-Contact Voltage Tester was reading power across the whole motherboard / phone once the Charging assembly was installed.
7. Haven't tried testing for shorts. Will need advanced help and reference points (have a multimeter).

Thanks so much in advance! I know this is a long read, but in my experience it gets us closer to a resolution faster if I'm more detailed in the beginning.

Thanks again,

Brian