I'm posting this with hopefully enough keywords so that other people can Google and find it, and so save themselves some time if they run into the same issue.
We have 8 identical workstations, each with a Lite-On SHM-165PS CD/DVD optical drive. One of these drives had the following symptoms:
- At BIOS (or in linux, or in Windows), pressing the front panel eject button would result in a couple of "clunks", and the tray might move a millimeter out, but the tray would not open.
- If the front panel button was pushed enough times, or linux "eject" was used, it might open eventually. If it did then pressing the button again and again eventually resulted in it working every time. Except that giving it even 10 seconds rest would put it back to the beginning.
- With no power, pushing a paper clip in the release hole would release the tray.
- The motor could be heard whirring when it was active.
- With front bezel and tray cover removed (and being careful to look at an angle, so that no reflected laser light would go directly into my eyes) I observed that during the clunking the emergency release was retracting, and then eventually returning to its original position just before the drive gave up.
The drive was removed from the machine and the top and bottom of the case also removed. The rubber band was intact and seemed tight enough. Even so, I tried replacing it with an O ring of the same size, as this solves CD/DVD tray problems 90% of the time. Unfortunately, it wasn't the solution this time.
To understand the repair one must visualize the tray mechanism, so please bear with me.
Picture the drive in the normal upright orientation on the table in front of you, with the tray opening towards your chest. There is a "locking rack" which runs left to right across the top/front of the drive just below the tray. It is easiest to see it with the tray removed. The left hand side of this rack contains the "paper clip" tray release mechanism. This consists of about an inch of linear gear teeth on the rack mated to 1/4 of a circle of teeth on the release lever/gear. On the right hand side of the rack there is a shorter run of similar teeth which (can) mesh with a gear driven through the rubber band by the motor. This driven gear meshes both with the teeth on the rack and with the teeth on the bottom of the tray. Slightly to the right of these rack teeth there is a small plastic pin which sticks up vertically out of the rack. This pin fits into a groove on the bottom of the tray, on the right side from the specified viewing position. There is an outlet in this groove which allows the pin to leave the groove when the tray is (nearly) closed.
Now then, when the tray is closed the rack is driven by the motor all the way to the left. The pin is out of the groove. Before the tray opens the rack moves to the right, driven by the gear. This also retracts the paper clip emergency release lever. The pin moves with the rack, engages into the tray slot lead in, by hitting a wall of that at a
45 degree angle, and this pushes the tray out slightly so that the tray teeth will engage the gear as well. As the tray moves the pin in the tray groove pulls the rack slightly farther to the right, which disengages the rack teeth from the drive gear. The drive gear stays engaged with the teeth on the bottom of the tray to open the tray.Careful inspection showed a series of very fine scratches on the tray groove where this pin engages/disengages. Figuring that scratches indicated something other than a smooth motion, a small amount of white grease (from elsewhere in the mechanism) was applied to the top and sides of the rack pin, and also to the 45 degree section of the lead in groove on the underside of the tray. This tiny amount of lubrication was all that was required to fix this problem.
Note that there is no evidence of grease on the lead in groove of the trays on any of the other drives. So I suspect the design intended that the interaction between the pin and the lead in groove 45 degree wall not require lubrication. However, apparently sometimes it does. The
45 degree wall in the lead in groove on the bottom of the tray can be (lightly!) greased without disassembling the drive if the tray is first opened with a paper clip.Regards,
David Mathog