When I turn on my macbook pro the logo appears in 30 seconds ( a bit long )

Hi,

I have a MacBook Pro 15" Retina ( Mid 2014 ), OS 10.10.3 Yosemite.

When I was turning on my macbook the logo appear in 5 seconds. I had an issue with some pixels on my screen and I sent my mac to repair in an authorized service. They repaired but since they repaired when i turn on my macbook the logo appears in 30 seconds instead of 5 ( before the reparation ).

They changed my hardware or WHAT? Why I have this issue?