No sound from iMac to receiver

[imacken]

Just today, I have stopped getting sound through my receiver/speaker setup via the optical cable on my 2011 27" iMac 3.4GHz i7.
Always worked fine till today.
1) If I remove the cable, I get sound through the internal speakers.
2) I get a red light at the end of the optical cable
3) if I boot into Windows via Bootcamp, I still get no sound
4) my receiver is set to the correct input
5) if I plug headphones into the same socket, the sound works through them OK.
Any ideas?

 

[Dreadnought]

The cable?!?! Try it wth another one

 

[imacken]

Yep, it's looking that way. Doesn't work when I plug my MBP into the receiver with the optical cable either.
It was an expensive cable too. I'll order another one later and see if that fixes it.

 

[imacken]

One thing though, surely if the red light is showing in the cable, then the signal is getting through.

 

[Dreadnought]

Could be broken somewhere down the line. Can you try it with an analog cable betweem the iMac and the amp, just to be sure if you do get sound?

 

[imacken]

Got a new cable today and it works OK.
Weird. The old one was expensive and fairly new with the red light showing.
Oh well..... thanks for your input.

 

[imacken]

Spoke too soon.
Sound has stopped working after being OK for a few hours.
Going to try the receiver with my Blu Ray see if it works with the optical output.

 

[imacken]

Not looking good.
I tried 3 things:
1) the receiver with my Apple TV using the optical in/out with same cable. Worked OK.
2) headphones in the iMac. Didn't work except after a bit of waggling of the plug in the iMac socket. Even then it was going off and on.
3) analogue lead from iMac to receiver. No sound except buzzing.
It's beginning to look like the Mac is at fault don't you think?

 

[jaxhunter]

What year is your iMac? The 2009-2011 models had their audio boards and audio ports as separate parts, both separate from the logic board. Not very expensive as I remember.

 

[imacken]

It's mid-2011.

 

[Dreadnought]

Could you check if there is any dust in the port. This can cause a bad connection. Shut down you mac and try cleaning it with an unfolded paperclip if you any dust.