hifi engine

Pioneer A616 Amplifier

Hi, I am having trouble with my amplifier. Ordinarily when you turn the power on a small click is heard after a few seconds and it powers up and starts working, Recently the click when turning on has been intermittent and when it does work it stops after a short time. When working it starts ok and then a pop or 2 and it stops. I have removed the top cover and blown it out with compressed air. Does anyone have any ideas on where I should look next. Thanks for any help in advance and Merry Christmas to all