Warning: You can render your drive and/or discs useless when you don't take precaustions.The first step is of course to get the drive out of the Xbox and disamble the drive itself.
|Remove the two torx screws on the back of the drive.||Remove the two screws holding the two metal lids together.||Lift the lid off, be carefull with the IDE and power contacts.||Remove the two screws on each corner of the drive that holds the PCB inplace.|
|Unclip the big and small ribon cable. The small cable may be fastened to the PCB, remove with care.||Lift up the PCB, be carefull with the two wires. Those are used to move the laster unit.|
Update: It seems like the Thomson drive never will play any CD-R discs, when I created this guide I only tested DVD+R media. Source.
Now you should have the drive disambled. Locate the POT meter shown on the picture below. The POT meter is locked with resin to prevent accidently or purposely adjustments, you will need to remove this with a small screwdriver. Try to get a good grip on the resin and it should come off completely, or else you can just poke and remove small peaces at a time. Eventually you will be able to use a screwdriver and turn it a few micrometer.
Now you can use your digital multimeter and set it to 0-2000 ohm or something with in that range. Points to measure: On bottom (large lid), seen from back of the drive, it's the only point on the right side of the POT. On top (small lid), move the laser unit back to the center so you can see the POT from top, it's the upper-left point. You might need to hold the drive vertically to measure both points.
|There is the POT meter, on this picture the resin is removed. The point you need to measure is on right side on the POT.||Remove the top lid, you might need to use a screwdriver unlock it.||POT meter seen from top. The second measure point you need is the upper-left one on the POT.|
When you got the points, the resistance should be around 1800-1900 ohm. Your goal is something between that and 800 ohm. Everything under 800 ohm should not be tried as it could damager the laser and the drive will make a lot of extra noise. Mine is 940 ohm. Mine copied a DVD+R with 4.23 GB of AVI files to a IBM 40 GB 7200 RPM harddrive in 23 minutes (3 MB/s).
Thomson tweak #1
Thomson tweak #2