Quality Control: Test Screen and Battery Before Fitting

A faulty part discovered after reassembly means doing the job twice: you have to reopen the device, lose time and reassure a customer who is waiting for their phone. A systematic check before fitting avoids many of these bad surprises. This method is meant for repair shops and resellers who regularly receive screens and batteries, whichever supplier they come from.

1. Inspect the part and its packaging on arrival

Before you plug anything in, look at the part. On a screen: chips, scratches, pressure marks, a warped frame, a folded flex cable, a damaged connector, a protective film that has been peeled off. On a battery: swelling, a deformed casing, a bent or corroded connector. Then compare it with the phone's original part: shape, position of the brackets and screws, position of the flex cables and connectors. Finally, check that the reference printed on the part or on its label matches the model you are repairing. A new part should also be clean: traces of glue or fingerprints, dust under the glass or tarnished connectors suggest the part has already been handled.

2. Test the screen before fixing it

Disconnect the battery before handling the flex cables, plug in the screen without gluing it, then reconnect the battery and switch the device on. Then go through the following points.

• Display. Using a display-test app or tool, show full-screen white, black, red, green and blue in turn. This reveals dead pixels, lines, stains, darker or yellowish areas and uniformity problems.
• Brightness. Raise and lower the brightness across the whole range. Flicker or an abnormal variation at low brightness is a warning sign.
• Touch. Draw lines across the whole surface, edges and corners included, test multi-touch (pinch, zoom) and check that no ghost touches appear when the device is lying on a table.
• Sensors and components. Depending on the model: proximity sensor (the screen should switch off during a call), ambient light sensor, earpiece speaker, front camera, under-display fingerprint reader.
• Features tied to the original screen. On some iPhones, features such as True Tone depend on data from the original screen. Check them and warn the customer before promising anything.

3. Test the battery

Start with the appearance. A swollen battery is never fitted, even if it seems to work: set it aside, away from any source of heat, and report it to your supplier. Then connect the battery to the device and check:

• that it starts normally, with no unexpected restarts;
• that charging starts and progresses steadily, by cable and, if the model supports it, wirelessly;
• that there is no abnormal heating, either while charging or in use;
• that the percentage is stable: no sudden drop and no shutdown while the displayed level is still high;
• the battery health indicator, when the system provides one.

On some models, a message about an unrecognised battery or part may appear in the settings after replacement. It does not necessarily mean the part is faulty, but you should tell the customer before the repair.

A full charge test is the most telling, but it takes time: keep it for large lots and for suppliers you are evaluating, and stick to a simpler check for everyday purchases.

4. Check again once the device is closed

After fitting, go through another round of checks: display, touch, charging, sensors. Put the waterproofing seals back where the model has them and check that the chassis closes without being forced. Do not hand the device back to the customer before this last check.

5. Keep a record of the results

Note the reference, the date of receipt and the test result, even in a simple notebook or spreadsheet. If something is wrong, photograph or film the fault, keep the packaging and contact your supplier before fitting anything: a part that has already been installed is harder to have accepted as faulty from the start. These notes also help you compare your suppliers over time.

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