A category B1 PART-66 /JAR-66 Aircraft Maintenance License shall permit the holder to issue certificates of release to service following maintenance, including aircraft structure, powerplant and mechanical and electrical systems.
Replacement of avionic line replaceable units, requiring simple tests to prove their serviceability, shall also be included in the privileges.
Category B1 shall automatically include the appropriate A subcategory.
The key words are Avionic LRU and Simple test.
It's up to your Pt 145 to define which tasks are acceptable under these rules. If in doubt don't sign for it , get a suitable qualified and experienced B2 guy to do it.