Most network problems are caused by SIM issues, carrier faults, or weak signal…
But a very rare case technicians encounter is this:
📉 After changing the phone screen, the device suddenly stops connecting to 4G or 5G,
and only stays on 3G — even in areas with full LTE coverage.
Here is a full breakdown and fix guide.
📡 1. Damaged Antenna Bridge Hidden Under the Screen Frame
Many modern smartphones have network antenna bridges embedded near the screen frame.
When the screen is removed:
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The bridge can shift
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The pad can lift
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The connector may lose contact
This causes weak LTE/5G reception, forcing the phone to fall back to 3G.
Fix:
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Remove screen and inspect the frame edges.
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Check for tiny golden contacts or spring-loaded pins.
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Clean them with alcohol (90%+).
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Apply light pressure to ensure contact before reassembling.
For safe handling of fragile components, see How to Fix Phone That Won’t Turn On (Step-by-Step).
⚙️ 2. Screen Replacement Blocking Internal Antenna Paths
Some aftermarket screens have thicker bezels or poorly cut frames, accidentally covering antenna lines.
When network antennas get partially isolated:
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LTE bands weaken
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5G fails completely
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Phone relies on 3G, the strongest fallback
Fix:
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Compare the old screen to the new one.
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Check for extra metal or plastic blocking antenna zones.
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Trim excess plastic if necessary (only if you are trained).
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Replace the screen entirely if badly designed.
See How to Identify Fake Replacement Parts — low-quality screens often cause hidden problems like this.
🔌 3. Misalignment of the Upper Network Antenna Plate
Phones like Samsung A-series, TECNO, Xiaomi, and Huawei use an upper antenna plate located near the front camera.
Removing the screen disturbs its alignment.
Results:
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4G disappears
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5G becomes unstable
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Only 3G remains consistent
Fix:
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Open the phone.
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Adjust or replace the small metal plate above the screen frame.
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Ensure screws are tight — loose screws weaken antenna contact.
Related: DIY Mobile Repair Kits — What to Buy & Avoid includes proper screwdrivers for micro-contacts.
🧠 4. Software Channel Reset Triggered by New Screen Driver
A very technical but real cause:
Some Android phones store network band calibration files that can be disturbed when a new screen driver loads (especially MTK devices).
Symptoms:
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LTE mode disappears from settings
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5G switch greys out
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Phone refuses to register on 4G towers
Fix:
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Go to Engineering Mode (MTK):
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Dial ##3646633## → Network Selection → Restore Defaults
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Reset Radio Interface Layer:
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Settings → System → Reset → Reset Wi-Fi, Mobile & Bluetooth
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Restart the phone
If you flashed firmware before screen repair, reflash stock ROM to restore band configuration.
🔋 5. Ground Contact Loss Between Motherboard and Midframe
LTE/5G antennas require strong grounding.
If the screen replacement disturbed:
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motherboard screws
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midframe fastening
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grounding pads
…the phone’s network performance drops drastically.
Fix:
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Ensure the motherboard sits flush on the frame
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Tighten all grounding screws
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Clean grounding pads with alcohol
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Test network with screws removed vs tightened
If performance changes, grounding is the issue.
🧩 6. Screen EMI Interference (Very Rare)
Some cheap screens generate electromagnetic interference that disrupts LTE frequencies.
This rarely affects 3G — which explains why 3G works fine.
Fix:
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Test with original screen
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If LTE/5G returns, the new screen is faulty
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Replace with a higher-quality display
🛠 Quick Diagnostic Method
Try this simple test:
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Insert SIM card
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Go to a strong 4G/5G area
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Lightly press the top-right corner of the phone
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Watch the signal indicator
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If LTE appears briefly → antenna contact problem
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If LTE never appears → screen driver interference or band miscalibration
This instantly helps you find the real cause.
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