NAD C541 Tray Won't Open

I just fixed one of these.
Made in China in 2000. Rubber belt dried up.
Went to Ace hardware and got o-ring #29 in plumber's section
My NAD works like new again.

The only problem is taking it apart.
4 black screws in the bottom come off.

Remember: do not force anything!!!
Tilt the back of the transport upwards and slide off the front of the tray - it goes upwards. Then you will be able to lift off the whole transport assembly. Toothed wheel in front will let you move the tray and open it all the way. Press the two little tabs outside and remove the whole tray. Now you see the belt! Replace it with the o-ring and you are good to go.

Additional info:
It seems that these players have a construction flaw. Look for D701 on the main board -- near the cables that run to CD transport. You will find in that place a small 7.5 kOhm rsistor. This should be a 6.2 Volts Zener diode instead. Replace the resistor with 6.2 V Zener and the tray becomes strong and fast.

Where can I order a 6.2 Zener Diode replacement for the C541? Also how many watts should it be? Also is this an easy fix or does one need a technician for this? Thanks