We were contacted about an electrocautery unit with a clearly broken selector knob — the kind of damage that's obvious from a photo alone. Once the unit arrived on the bench, it was time to work out the best way to put it right for good, rather than just patching it up.
The broken knob sits on the shaft of a rotary encoder, the component used to select settings on the unit. We did consider a quick fix — reinforcing the broken shaft with an insert and glue — but ruled this out quickly. While cheaper, it would almost certainly snap again, likely sooner rather than later, and probably at the worst possible moment during a procedure.
Getting the rotary encoder out also wasn't straightforward. The front control panel board had to come out first to access it, and the encoder itself was connected via a small riser board that needed careful unsoldering — first from the main panel, then the encoder from the riser.
With the faulty encoder removed, the next step was sourcing an exact replacement. This particular encoder has several variations even within a single model from the same manufacturer, so getting the spec right was critical. It's available from several suppliers including Farnell, but with some smart sourcing we found the same part for around half the price.
Fitting the new encoder was the reverse of the removal process. While we had the unit open, we also took the opportunity to straighten out a fairly significant dent in the front panel that had built up over time.
The unit was returned with a new, correctly specified rotary encoder and a straightened front panel — a proper, lasting repair rather than a stopgap that would likely fail again. We've now repaired several electrocautery units with this kind of damage, so if you've got a broken selector knob or switch, it's a job we know well.
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