Causes of thermal shutdown is B/M : 1) Improper air flow 2) Exhust air choked. 3) if system is located above 80 degree place. 4) vent is choked by dust. 5) CPU or Video card fan faulty. 6) Fan spin but speed is not proper. 7) heat sink degraded by thermal paste or greases.
When I connect an external microphone to the jack, it is not working. I can see it in the "Sound" tab, but the levels is very low. I have tried with several microphones.