Hi
to see if the signal is getting to the cd module, open the lid, an watch the laser lens as you power on it should vibrate immeditely as you power on,if it does then power is getting to the cd module.
The laser might be burnt out, you can try tweeking the laser potentiometer (yellow pot under the lens)slightly mark its position first with a black marker,then turn it (2 minute intervals ) anitclockwise to see if that helps to read the cd.