NAD 5240 cd player problems

[bmwdriver325i]

I have two problems with this cd player, with some cds it has trouble tracking, and it will not play cdr's though I've read that it can, second the display is gone, if you look really close with a bright light you can see it but it does not emit any light, any help would be much appriciated, thanks

[Extreme_Boky]

Hi,

Re tracking problem:

Not all CDs have the same reflectivity. CD-Rs have even lover. The laser diode looses its ability to output a proper (high enough) laser beam.
Check your PCB and look for a test point labelled RF. Insert a CD that your CD player has problem reading. Monitor the RF signal on oscilloscope and look for an eye-pattern. It should be 1.5(+ or - 0.3) Vp-p. If it is lower than 1.2V you'll have the problem where the pick-up reads some disks, and does not read ones with low reflectivity. You can increase the laser output by adjusting the little trim-pot located on the pickup itself. Do not go over 1.7 - 1.8 volts. After adjustment try CD-R disk and check the amplitude.

Re display problem:

Your display should have 'heating' voltage (usually labelled F1 and F2) of around 3 or 4V AC - check if this is present. Displays also use -33V DC or close to this value, and sometimes + or -5V DC as well. With your CD player being made in UK, check for burnt-out resistors in the heating circuitry.


Good luck!
Regards,
Extreme_Boky