iMac 27" Volume Control only Works with headphones.

[Sadspy]

Hello. I have a 27" iMac running Snow Leopard. A few months ago I noticed that I could not control the internal speakers volume. It was set to a volume but I could not control it tho' the volume display changed in the screen normally. When I plug my Sony headphones I can control the volume but when they are not plugged it does not work. Sometimes it comes back to normal after a restart or something, but most of the time the problem persists. Is there a permanent solution for this? Is this a hardware or software problem?
-Sam

 

[derek1997]

I have had the same problem with my iMac running lion.
I don't know if this just works for me but have your wireless keyboard and mouse off until your Mac is Fully powered on and is at the login screen.
Once again this is what helped me I don't know if it will help you but it is worth a try.

 

[iDabble]

Go not your sound settings under system preferences and make sure your audio output channel is correct.