Scanners use cold cathode lamps to illuminate the images that they are scanning so that a special IC (Integrated Circuit) can scan them. In most cases, when a scanner breaks, part of its scanning and/or computer connection hardware is damaged, but the cold cathode light and power inverter are often in pristine condition. By extracting them and wiring up a simple circuit, we can get ourselves a virtually free (Unless you were forced to pay a few dollars for the broken scanner) cold cathode lamp.
First, I took apart the scanner, and removed all of the circuitry. Then, I removed the stepper motor and took out the light assembly. This is probably the only part that you will need (unless you decide to reuse some switches and power connectors from the main board of the scanner). Next, I extracted the cold cathode lamp and its power inverter (a small circuit board with a transformer and some capacitors and coils). After that, I stripped the input leads to the inverter, connected the scanner's original power supply to the wall, and used the stripped leads to test the lamp. Note that ifyou connect the leads the wrong way, you will destroy your power inverter and you won't be able to continue. To see which way you need to connect your wires follow these instructions:
1) Look that the colors of your stripped wires. The black one is ground (negative -) and the other colored one (often red) is the positive input (+).
2)After you have determined the polarities of the input terminals to the inverter, look at your power supply (the one that plugs into the wall). There should be a small diagram that you can see in the top right of the second picture in the slide show. It will tell you whether the outside and inside of your power connector are positive or negative.
Once you have figured out all of your polarities, simply hold the input wires of the power inverter onto the correct sides of the power supply connector. If you did everything right, the cold cathode light should light up. If however you connected something the wrong way, you will see some smoke come out of your power inverter and that will mark the end of its life.
Once you've gotten the cold cathode light to work, simply solder on a power switch in between the power inverter's inputs and the power supply's output. After that, add a female power connector so that you can plug in and unplug your power supply. Once you've done this, I recommend using hot glue to cover up all of the contacts (to prevent any unnecessary electric shock or accidental contact)
and mounting everything inside of a project box (I used an altoids tin).
And... You're done!
Possible applications include:
1) Using to illuminate computer cases; use this instead of a $15 commercially sold cold cathode lamp)
2) Book light
3) Computer keyboard illumination
4) And much, much more!
PS: Instructable coming soon!