By Deepa Seetharaman SAN FRANCISCO (Reuters) – Seattle audio and video technician Todd Mueller showed up last year for what might have been a routine job except for one thing: Amazon.com Inc was taking notes. As he mounted a flat-screen TV on the wall, an Amazon employee studied how he covered his shoes and used a blanket to protect the hardwood floor. After at least two years of study, Amazon is ramping up efforts to offer repair, installation and other services online, tackling a fragmented but potentially rich U.S. market that may be worth an estimated $400 billion. Amazons experiment with services goes back to at least mid-2012 in its hometown of Seattle.