Dead pixels and bright spots
A dead pixel is a pixel that stays dark, and a bright spot is a pixel that stays lit, both caused by a fault in the pixel's transistor or connection. A single dead pixel may be hard to notice on a large screen, while several together, or one in the centre of the screen, will be noticed quickly. Dead pixels are a manufacturing matter, and a buyer who finds them should describe their number and position accurately, with a photograph if possible, so the supplier can judge whether they fall within an acceptable range or warrant replacement.
Bright spots differ from dead pixels in that they draw the eye: a bright pixel on a dark screen stands out, while a dark pixel on a bright screen may blend in. A buyer who reports a defect should say whether the pixel is dark or bright, where it is on the screen, and how many there are, because those three facts determine the response.
Backlight and colour problems
Uneven backlight shows as brighter and darker patches, especially on a plain screen, caused by the backlight's distribution or by pressure on the panel. Colour shifts show as a tint across the screen or in one area, caused by the panel's calibration or by a fault in its colour filters. Both are visible on a plain test screen, and a buyer who reports them should say which test screen shows them, and whether they appear on all inputs or only one, because that narrows the cause.
Lines across the screen, whether horizontal or vertical, usually point to a connection fault: a loose or damaged cable between the panel and its driver, or a fault in the driver itself. A line that appears and disappears when the screen is moved suggests a connection, while a line that stays constant suggests a panel or driver fault. A buyer who reports a line should say whether it moves, whether it is horizontal or vertical, and whether it appears on all inputs.
What to do when a defect appears
Describe the defect accurately: its type, its position, its number, and the conditions under which it appears, with a photograph if possible. Then ask the supplier, naming the exact model, for the remedy that applies to that model: whether it is a repair, a replacement, or a calibration, and what the warranty terms say for that model. Do not attempt to open the panel yourself, because opening it can void the warranty and can damage it further.
A defect report that is vague — a screen looks wrong, without saying how — will receive a vague reply, while a report that names the type, position, and conditions will receive a specific one. The troubleshooting guide explains the steps to take when a touch screen stops responding, and the inquiry pages list what to confirm before ordering.
Before payment, confirm the minimum order quantity, lead time, payment, shipping and warranty terms for your order. Certificates are available upon request.
Keeping a record of defects
Keep a record of every defect found: the model, the date, the defect type, its position, and a photograph, because a record turns isolated complaints into a pattern that can be acted on, whether the pattern points to a batch problem, a handling problem, or an installation problem. A single defect may be a one-off, but several defects of the same type in the same position across several units point to a systematic cause, and a supplier who receives a record can investigate that cause, while one who receives isolated complaints cannot.
A record also protects the buyer: a warranty claim supported by dates, photographs, and descriptions is harder to dispute than one supported by memory alone, and a buyer who keeps records will resolve claims faster than one who does not. Records cost little to keep — a photograph and a few lines per defect — and they pay for themselves at the first claim that would otherwise be disputed for lack of evidence.