From the situation you've described, it appears the primary issue might stem from an incompatibility between the replacement display and the phone's original hardware. Here are the key points and steps to diagnose and potentially resolve the problem:
# **Problem Analysis:**
1. **Display Incompatibility:**
- The original display that was replaced had the model number "SM-127F," while the new display has "SM-A022F."
- Samsung Galaxy models sometimes have slight variations between different batches or regions, leading to different connectors or pin configurations. Even if the parts appear similar, they might not be fully compatible.
2. **Possible Connector Issue:**
- You mentioned there might be glue around the pins of the cable connector. If glue or any residue is present between the pins, it could prevent proper contact, leading to the display not functioning correctly.
3. **Potential GPU/Logic Board Damage:**
- Since the phone fell, there’s also a possibility of damage to the logic board or GPU, which could cause the display not to work even if the display itself is fine. However, this is less likely compared to the other issues.
# **Steps to Diagnose and Fix:**
1. **Check Compatibility:**
- First, confirm the exact model of the original and replacement displays. If you ordered the wrong model, you may need to return the display and get the correct one (SM-127F for your device).
- Use the other functional Samsung Galaxy A12 to test the new display. If the new display doesn’t work on the fully functional phone, it confirms that the display itself is incompatible or defective.
2. **Inspect and Clean Connectors:**
- Carefully inspect the connectors on both the display and the logic board. If there’s glue or debris, clean it off using isopropyl alcohol (90% or higher) and a soft brush. Ensure the pins are not bent or damaged.
3. **Test with the Old Display:**
- Even though the old display is broken, if it can still show some signs of life, reconnect it to see if it behaves differently than the new one. This can help determine if the problem lies with the new display or elsewhere in the phone.
4. **Check for Other Hardware Damage:**
- If possible, check the logic board for any signs of physical damage. Look for cracks, burnt components, or loose connections. This might require a professional if you're not experienced with hardware repair.
5. **Consult a Professional:**
- If after cleaning and testing the components the problem persists, you might need to take the phone to a professional repair service. They can conduct more advanced diagnostics to check for issues like a faulty logic board or GPU.
# **Next Steps:**
- If you identify that the display is indeed the wrong model, contact the seller to arrange for an exchange or return.
- If cleaning and testing the connectors solve the issue, you can proceed with reassembling the phone.
- If none of these steps work, consulting a professional is advisable, as they can perform repairs or further diagnostics beyond basic troubleshooting.
This approach should help you systematically identify the root cause and get your phone back to working condition.