It's probably not outputting I2S - either that or the I2C is dead. Both I've seen; I2C is usually either a dead LVX04 or a bad pull-up resistor (the respacks sometimes have bad solder joints). I2S problem is usually a solder issue or a bad PEEL - we've got loads here though.

I2C problem is obvious if you look at a boot log, you'll see loads of I2C failures and the volume control will be v.e.r.y slow due to all the error printing.

I've only ever come across one dead DSP, and I have no idea why it died. We've got spares here, though.

Hugo