Dead row or column: the swap test that names the culprit

A dark, stuck or wrongly coloured horizontal row or vertical column is a localized fault in one module or in what feeds it data. A single test — swapping the module with its neighbour — almost always settles it.

Read the fault before opening anything

A dead row on a single module comes from that module: faulty driver IC channel, row-scan MOSFET, or tired solder joint.

The same dead row crossing several aligned modules points to the flat cable or the HUB board feeding that row.

A column lit permanently regardless of content — the « caterpillar » — is the signature of a shorted LED. A « cross » appearing only when the pixel should light signals an open-circuit LED.

The swap test, step by step

1. Power down the cabinet concerned.
2. Unclip the affected module and a healthy neighbour from the same cabinet (magnetic or screwed depending on model).
3. Exchange their positions and power back up.
4. The fault followed the module: order a spare of the same reference, same batch if possible.
5. The fault stayed in place: swap the flat cable, then as a last resort the HUB board.
6. Note the exact position (cabinet, module) for the report and the parts order.

Beware of VH voltage

Never try to « rescue » a weak row by changing the VH voltage at random in the software: only the manufacturer's value for the exact driver IC is valid, and a mistake degrades the whole wall. In doubt, escalate.

When to call an engineer

Module swapped with no change, rows that come and go with temperature, or several rows in unrelated areas: the diagnosis deserves an expert eye before ordering parts.

Frequently asked questions

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