No sound on Inspiron 3542

Hello!

I have a 2 questions:

1. I bought Dell Inspiron 3542 Laptop with Ubuntu 12.04 LTS. At first launch it ask me to update. I agreeded to update. After updating is no sound integrated dynamics. But if I attach external dynamics, sounds exists.

2. Also update-manager asks to upgrade to Ubuntu 14.04.4 LTS. On time I try this, but updating failed and I haved to return laptop to factory state with Ubuntu 12.04 LTS.

Thanks!