What actually fails, in order
Across our service records for indoor walls, the first three failure categories are power supplies, receiving cards, and cables. LED modules come fourth, and most module failures are mechanical damage rather than electrical failure. That should shape what you stock.
A realistic spare ratio
| Item | Recommended spare | Notes |
|---|---|---|
| LED modules | 2 – 3 percent of total | One per cabinet colour batch is enough |
| Receiving cards | 2 per wall | Plus one per 20 cabinets |
| Sending card | 1 per wall | Most critical single part |
| Power supplies | 3 percent of total | Derate them, they fail in heat |
| Cables | 4 short, 2 long | Cheapest insurance in the kit |
Why 10 percent modules is wasteful
Modules are durable and interchangeable within a batch. If a module fails, you replace one, not ten. Holding 10 percent means 90 percent of that stock will still be in the box when the screen is retired, and by then the batch may not match the wall colour.
The batch problem
Spare modules must come from the same production batch as the wall, with the same colour bin. A module from a different batch can be visibly different, especially on a white field. Order spares with the original order, not a year later.
What to do if you cannot hold spares
Buy the small kit: one module per colour batch, two receiving cards, one sending card, four cables, two power supplies. It fits in a shoebox and costs roughly 2 to 4 percent of the wall. For a site with a two-week shipping lead time, that kit prevents almost every long outage.
The maintenance contract question
If you do not want to hold anything, negotiate a response-time clause instead: for example, parts dispatched within 48 hours. That is a different product from a warranty, and it should be priced separately. Ask for it in writing with the specific part categories covered.