Which is the verb for technician?

There isn't a single verb specifically for "technician." Instead, we use verbs that describe what a technician *does*. Here are some examples:

General:

* Repair: A technician repairs electronic devices.

* Maintain: A technician maintains the machinery.

* Service: A technician services the air conditioning unit.

* Troubleshoot: A technician troubleshoots computer problems.

* Install: A technician installs new software.

Specific to a particular field:

* Diagnose: A medical technician diagnoses illnesses.

* Calibrate: A lab technician calibrates instruments.

* Program: A computer technician programs software.

* Weld: A welding technician welds metal parts.

The best verb to use will depend on the specific context and the type of technician you're talking about.