Scope_img_Rayclock_osc_small.jpg  CD clock PCB  Scope_img_Rayclock_osc_small.jpg

This CD clock is very easy to build. The oscillator-part is based on that of the Kwak-clock by Elso. The circuit has been adapted to make it work on a single supply voltage. The power supply is that of the XO-module as presented on the Tentlabs website.

This two-stage regulator supplies voltage for a J-FET oscillator and a comparator. The oscillator uses the original crystal from the player. The sine-shaped signal is converted into a square wave by the comparator. A supply voltage little over 5V ensures the output singal is almost 5Vtt. This is taken from pin 8 of the comparator and connected to the clock-input (CKI) of the DAC through a 47 ohm resistor. With P1 the square wave can be adjusted for a 50% duty-cycle.

The supply voltage can be obtained from the player itself, but a separate supply will give better results. The circuit needs a minimum input voltage of 11V. If needed this can be lowered a bit by using a low-drop regulator instead of a 7808 (like LM2937 or 2940); this was nescessary in the CD52 for example, because the available voltage was a little too low. In that case C2 needs to be enlarged to 22...47uF because low-drop regulators require a larger output capacitor to remain stable.

Fitted examples

The schematic and the PCB-layout, version 1.0