Bose lifestyle 5 do not power up

hello everyone,
I hope you will help me find the faulty part on my Bose 5 lifestyle Music center. something happened one day and i lost the power supply 12v and the bose doesnt turn on.
I bought a new 12v adaptor but still have the same problem, I have opened it and kept testing faulty parts but i couldnt know which one is down.
would you please help find it.
thank you