Does not recognise disc

Hi, firstly check that the discs are not too scratched and be aware that CD's read and play from the inner diameter to the outer diameter. CD players are really finicky devices that can be affected by the slightest bump and also temperature and humidity changes. Sometimes decks have a humidity sensor embedded in the circuitry. So, all that being said, firstly just turn the set on and let it sit for a while to heat up and dry out especially if it hasn't been used for a while. Then, take the lid off and check for broken drive belts that actually spin the disc. (You may be able to hear the disc spin without the top off). After that the laser itself will have to be cleaned, adjusted and the current checked. Lasers do wear out and sometimes increasing the current to the laser will make it read for a little while longer. You will need the schematic diagram and some decent equipment and knowledge to achieve this though. Since they both don't work, and you got them for free, they might be good experimental pieces but, in my experience they are never 'time' worthwhile repairs. Good luck. Cheers

you want expert opinion free LOL that does not happen .we are mostly diy fixers and do not get paid

HI ALL YOU NEED TO DO IS PUT IN A CD/DVD LENS CLEANER CAUSE NOW ITS DIRTY THEREFORE THE LASER IS UNABLE TO READ THE DISC.

The lazer is not reading the disc, It is shot.

Dave, Holding the motor spindle / laser assembly in a position where the white ribben plug in receptacle is facing in an upward position, look down to the lower left hand corner of the print board just under the plug in. You will see a small blob of solder bridging two contact points. Remove this solder bridge. I have found two new Denon assemblys with this problem.........*****

It sounds like its not reading the disc, most the time that is caused by a bad processor and that isn't something you can fix yourself

Then the format can't be read by the MAC, what reason this is I have no idea.

Sounds like your spindle motor is shot. What happens is, the bushings in the motor that turns the CD disk are worn. So tilting the unit will change the loading of the motor shaft to an " un-worn" spot on the bushings and the CD plays properly. The spindle motors are chepa for the most part, but the labour might bite you a little because it is a fairly involved job. If the unit is still under warranty....great...if it is just off warranty, you may get some good will service from Denon......best of luck...Rob

You seem confident enought to take it apart, have you tried cleaning the runners that the laser runs backward and forward on.
Some times they collect dirt/dust and the laser can't move smoothly so it jerks and skips.