acer aspire 5750 headphone-microphone jack not working

[mar1za.aro]

I have an Acer Aspire 5750, which has one input for headphones and microphone.. when i insert my headphones the sound continues to exit from the speakers.. I tried both smartphone headset and normal headphone, still nothing happens!! thank you

 

[helpstar]

Did you plug in the headset to the right connector in this picture? Be sure the headset do have a 3.5" jack and not a 2.5" or similar.
https://static.trustedreviews.com/94/77f2e3/79cf/IMG-0960s.jpg