LG GSA-4120B servo motor replacement

The drive stopped recognizing discs by itself. After closing the tray there is a buzzing noise, progressively getting louder/higher pitched, but the disc is not spun up or recognized; the laser does not even turn on. Similar buzzing happens before the tray is opened.

Pushing the lens sled along a bit causes it to move and do it’s thing, and even spin up the disc, recognize it (after a while), etc. Rarely it’ll recognize a disc by itself without having to push the mchanism.

Reading a disc gives CRC errors, burning fails at 3-4%, mostly before anything (it seems from looking at the disc) is written. I’ve made several coasters already. Simulation sometimes succeeds.

I figure that the servo (stepper) motor is broken, perhaps one or more of the coils is dead or weak. When the lens sled is in such a position that the weak/broken coil is the one to be energized to get the thing moving, nothing happens. Pushing the sled manually rotates the motor until a good coil moves into the right position at the right time and is energized and the sled is set into motion properly.

I’ve taken apart another CD drive to see if I could get the servo motor out from it to fit into the LG, but no luck: the bracket mounting holes are placed in such a way that I can’t put it in the LG. So I can either try to pry the motor off the LG bracket (and screw on the one from the other drive), or put in a bracket from a different drive.

Any suggestions for donor drives with same bracket configuration as the LG? Any suggestions for getting the LG motor off its bracket?

This might not be a servo motor problem after all, but a chipset/electronics problem, in which case there is not much I can do. I’ll most likely be getting a new drive anyway, but I could still make good use of this one, and would like to fix it.


Unless you can get hold of a load of other drives for next to nothing I would say your best bet is to just bite the bullet, and get another unit, they are not a lot and I would have thought less than the cost of a new drive motor :frowning:

It could be something simple as carbon deposited on the armature that you could just clean off, if your willing to pull the motor apart (I would not do it on a ODD) or it could be the windings burnt out …or it could just be the drive wheel/gear on the tray/sled itself or any number of things between.