• Grundig CDR100
• HP 4020i

3.10) HP 4020i/Philips CDD2000 Spring Fix for Write Append Errors

(From: Rick Richardson (rick@dgii.com)).

The first step is to remove the case. Remove two screws with the T-10 screwdriver and four screws with the T-? screwdriver. Remove metal case. Gently release the top circuit board from two plastic alignment posts -- this may require gradual rocking of the circuit board but do not stress the circuit board as it is very thin.

The next step is to remove the main circuit board by disconnecting three ribbon cables and two sets of two pin connectors. The larger ribbon cables are released by moving two pieces of plastic at each end of the cable connector away from the connector body by about 1/8". The cables should then easily slide out of the connector. The smaller cable has a slightly different release mechanism, but again just move it about 1/8" away from the connector body. Slowly rock the two pin cables from their sockets.

You should now be able to see 4 more T-10 screws. Remove these to free the drive mechanism from the other part of the metal case.

The next step is to remove the smaller circuit board on the laser transport assembly. Remove 4 philips head screws. Pull the board up and lay it over - you will not be able to fully remove the board because two wires are soldered to the motor.

If you look at the transport now, you will see a worm gear which drives a regular gear which drives a rack gear. The rack gear is spring loaded to press up against the regular gear. According to theory, the spring which causes this pressure is worn out and/or not designed to be strong enough.

The spring itself is a straight length of springy wire, about 1" in length and rumored to be about .012" in diameter. Since I don't own calipers, I couldn't verify this.

The spring is held in place only by its springiness. Each end fits into a slot and the middle is bowed down an under a notch in the plastic rack gear.

What you want to do is add a second spring wire. You should not need to remove the original spring wire. I found a suitable wire in a 5.25" floppy drive I had laying around. I removed the wire from the floppy drive and straightened out a couple of bends that were in it and ended up with a straight piece of springy wire about 1.25" long, which is longer than the spring in the CD-R drive. You want it longer for now because it is easier to install it that way. It will be cut to length later. Use the two pairs of needle nose pliers to straighten the spring wire.

With your finger, rotate the worm gear on the shaft of the motor to move the transport carriage so that the center of the spring is under the center of the regular gear. You should be able to see the notches that hold both end of the spring now.

Lay your new spring on top of these notches. Using the blade of a small screwdriver perpendicular to the length of the spring, press the spring down in the middle until it is underneath the slot in the black rack gear. This bows the spring about 1/8" in the middle. The spring should now be in place.

Using your smallest dikes, cut the ends of the spring wire off so that they are the proper length. Wear eye protection when doing this, and if possible grasp the end being cut off with needle nose pliers so that the wire won't fly around the room or worse into the drive mechanism.

With the drive still opened up, use a can of compressed air to blow off the dust on the laser lens. DO NOT touch the laser lens as it is magnetically floating in its holder.

Now, reassemble the drive by reversing the disassembly instructions.