A control board fails on a Friday. The OEM quotes a replacement at a serious price and a ten-week lead time. There are three real options, and the cheapest one is not always right.
Option one: component-level repair
Most industrial board failures are a small number of components — power supply sections, output drivers, electrolytic capacitors that have dried out, and connectors that have corroded. Repair typically costs a fraction of replacement and turns around in days rather than months. The condition is competent diagnosis: the repair has to find what killed the component, not just the component that died.
Option two: replacement
Replacement wins when the board is still in production at a sensible price, when you need multiple units, or when the failure is so widespread across the board that repair economics collapse. It is also the right call where the board's failure is a symptom of something upstream that will keep killing boards until it is fixed — in which case buy the board and fix the cause.
Option three: redesign
When a board is obsolete, repeatedly failing, and no replacement exists, redesigning the function is the durable answer. It costs more upfront than a repair and delivers something the other options cannot: a supportable board, with a documented BOM of currently available parts, that you can have made again in five years. For a machine with a decade of life left, that is usually the correct economic decision.
The question that decides it
Ask how long the host equipment will remain in service. Under two years, repair and move on. Over five, with the board obsolete and failing more than once, redesign almost always wins on total cost. The middle ground is genuinely a judgement call, and it should be made on spares availability rather than on the invoice in front of you.
Whatever you choose, fix the cause
Boards that fail once tend to fail again, because the environment that killed them has not changed. Supply transients, cooling that has degraded, moisture ingress, vibration on a connector — the board is often the victim rather than the culprit. Any competent repair report should name the cause; if it does not, ask.