NAD CD Player - How a CD player works ( laser unit replacement ). 

Thanks for the compliments, and thanks for watching, Regards Hendri

Hi Andrey, great thing to fix the tray-issue! What did you do? Belt exchange? My NAD c521i player is great working, exept ejecting the tray. Motor for the tray is working, but does not get any voltage when pushing the eject Button…

Do you have any idea?

@@peterstoeful In my case, the incomplete disassembly of the mechanism helped, as far as I remember, the whole thing was in the limit switch I'm afraid it will hardly be useful to you, best wishes

@@andreydavydov6417 ThX!

Good to hear, glad you did it your self. Best feeling to fix someting DIY. Hope to load more video's. Thanks for watching.

Thank you too!

Hey, if you still have it, you may find the drawer is stuck because one of the belts has degraded and become slack. Open the lid and study the CD loading, looking for slippage on the pulleys.

The laser focus might be broken (fairly common failure mode), but it's also possible that the laser tracking motor on your transport, or the "null" microswitch that locates the laser in it's "parked" position are faulty. The laser beam is focused down to a small 0.9 micron diameter beam to read the pits which vary in length. The disc can be warped or misloaded by as much as 0.5 mm, and the focussing solenoid has to have sufficient movement to accommodate this. Hendri shows the focussing lens moving up and down. Your disc could be warped by more than this and it would exceed the compensation available in the focussing system. The main CD spindle could also have worn bearings, like an out of balance wheel, and it would be impossible for a laser to track the CD as the wobble will increase with the laser moving to the outer edge of the disc. With the laser tracking across the disc itself - that uses a separate mechanism - either a radial arm like a record player conventional tonearm, or a rack and pinion like a parallel tracker tonearm. You can see Hendri moving the rack and pinion in the video. It's worth stripping the mechanism down, removing the dried up old grease with isopropyl alcohol and relubricating with fresh grease, as you would when servicing a mechanical watch. But if the motor or microswitch has failed, it's probably a brand new transport that will be required. It's very unlikely to be a firmware or hardware (chip) fault, that would knock out the whole player and a power or magnetic surge would also take out any nearby equipment as well, not just the CD player by itself. Is the player right next to a loudspeaker or CRT TV? If so, the stray magnetic field may be causing the problem, and preventing a hall-effect switch from working.

You can't adjust the output (well you can try increasing the current but you'll just end up frying the chip that powers the diode so it's not a solution - it would be like running your car on Jet-A aviation kerosene, it will just blow up from the additional heat). The laser is a semiconductor diode, and when it's stopped lasing it means all the electrons and holes in the doped P-N junctions have changed energy levels and the diode is effectively "exhausted" or dead. Much like a typewriter ribbon that has all the impregnated ink used up or a turntable cartridge stylus that's had all the diamond worn away. The process usually takes a long time, typically a CD semiconductor diode has 10,000 hours of life which equates to a 10 - 15 year lifespan, but once the diode has stopped outputting light, that's it - game over. The only solution is a brand new laser pick up fitted with a brand new laser. And a fresh 10,000 hours of life.

The motor is either broken, or isn't getting any power.

use fine cloth!

No. Lasers are specific to individual transports. A Sony transport uses a different laser pick-up to a Sanyo, Philips or Toshiba. DVD drives that can also read CD's as well are a whole different kettle of fish - they pack two lasers into one pick-up. And then there's Blu-ray, using a third completely different wavelength of light. CD uses 780 nanometres, DVD uses 650 nanometres and Blu-ray uses 405 nanometres, which, being violet, it should be re-named "violet-ray". A CD only player cannot replay DVD's or Blu-ray discs because it's laser only emits 780 nm light. A DVD player might (or might not) be able to re-play CD's depending on the laser pick-up fitted, as the laser has to be multi-wavelength (essentially two separate lasers built into one laser pick-up, with a shared photodiode detector to measure the reflected light off the disc. Most "Violet-ray" players are only able to replay that format, it's not physically possible to shrink 3 separate lasers (with their own wavelengths) into the available space.

Almost certainly a compact disc with CD rot. I.e. the Aluminium reflective coating has oxidised and turned into dull non-reflective aluminium oxide. This was a common problem when the CD manufacturers failed to encase the aluminium with a resin top coat, leaving the aluminium to slowly oxidise from the disc edge inwards. It ruined a lot of discs pressed by Du-Pont Optical at the Philips plant in Blackburn. If you're lucky, you've got a disc where the oxidation doesn't encroach onto the disc inner segment where the data is read from. If you're unlucky, the whole disc turns a dirty bronze colour and won't reflect any light back to the detector photodiode.

Thanks for the info-I’ll try a different cd and see if it makes a difference