Using ASUS M2A-VM HDMI mobo with onboard video + sound
Sound through SPDIF port in riser card to digi coax port in HT receiver
Its been working for months and I haven't been tinkering!
All of a sudden - no sound of any kind coming from the HTPC - whether in windows or media centre. Any ideas / troubleshooting tips?

You said no tinkering, which is good, but how about windows updates?

Either way, you might just try unplugging/plugging the riser card.

Windows updates are set to automatic, so definitely a possibility.

Other possibility is my 2 rugrats - my HTPC case has a 7" touch screen which they love to play with, but I usually turn off. This incident occurred under the supervision of my wife so I am suspect!

When you say unplug/plug the riser card - should I boot up in between?

I would first check RealTek setup to make sure you are still on the correct options.

2nd would be to unplug and replug the connector into the optical/digital card.

3rd would be to open the case and make sure the connector is securely on the mobo and on the riser card.

If you are unplugging a card you should have the power off, so that would imply a reboot.

If all else fails, blame the wife. :)

So I've been looking at all the audio settings, drivers, etc

Went to the basic Windows volume settings, and noticed that the SPDIF is greyed out - all others are active - Master, Centre, Left, Right, Subwoofer, etc

Any idea how I can 'reactivate it'? Only thing I can think of is going in the BIOS, which I can't do right now because I have an IR keyboard which doesn't seem to work until Windows boots up, so I will have to find a basic keyboard to get into the BIOS.

Any other ideas?

I've had this setup working for almost 6 months+, and haven't physically tinkered with it. I've checked the connections with the HTPC and HT Receiver.

Is there a RealTek control panel? Try to see if you can turn on SPDIF there.

Also check the speaker settings in the Windows control panel to see if something has changed there.

I had spdif before on same mobo and I think it is normal to be greyed out.

What you need to check is in Realtek screen that you have 5.1 speakers and then go to Audio I/O and click on X beside Digital. There you make sure that you don't have "no SPDIF output" checked. There is also volume control in another screen which you should make sure SPDIF isn't muted or low.

Failing that. I would do what I suggested before.

ANother thing that I thought of. What if the kids played with your A/V receiver. You should double check that. On my receiver it is easy to press one button on the front panel which changes digital to analog for a certain input.

Good luck

Q

Another thing to check in Realtek options is whether it is set to 96khz or 48khz. I don't think the reciever will output sound if it's set to 96khz.

Depends on the receiver... my Onkyo will take either.

Q's suggestion is good. Make sure the receiver isn't switched to Zone 2 or the A/B speaker switch was pushed.

You guys rock! After checking all the HTPC audio configurations, I focused on the A/V receiver. Sure enough, they messed up the settings for the digi coax input. Problem solved, thanks everyone!