On the cold cathode
subject I'd just like to point out where this comes from. It's not really snake oil, but rather a technical term that really only an electronics technician could care about.
If you look at a standard household fluorescent light, you will notice that there are two pins on each end of the tube. Inside, these pins connect to what looks like a light bulb filament in each end of the tube. And indeed if you apply power to the pins on one side of the tube, that filament will glow in the end of the tube.
This filament is known as a heater, and it is specifically there to warm up the gases inside the fluorescent tube. Fluorescent lights are hard to turn on when cold, but start easily when warm, so the filament in each end helps quickly heat the gas up to operating temperature.
In vacuum tubes where direct current (DC) power is used, the positive pin is called the anode
, and the negative pin is called the cathode
. Since fluorescent tubes use alternating current (AC), both sides of the tube are cathodes (there are no anodes). The whole heater assembly and the two pins are a cathode.
Now, you CAN turn on a standard fluorescent tube without using heaters. It just takes more voltage and current to get the tube to start producing light. Most portable fluorescent lights powered by batteries actually use bi-pin tubes with heaters in them, but the heaters are not activated and instead a higher voltage than normal is used to start the lamp.
Fluorescent tubes with only a single pin on each end do not have heaters, and obviously cannot heat the gas prior to starting. These are the cold cathode tubes you hear about.
The team cold cathode has nothing to do with how warm the bulb gets in operation. For case mods it's just a small and compact design where you don't have much room to begin with, since heaters would necessarily make the tubes bigger and fatter.
The snake oil aspect for me is that I really don't think most case-light tubes are fluorescent at all. Instead many such as the the red ones seem to be neon tubes where the gas itself produces light rather than a phosphor coating making the light. Fluorescents actually contain a mercury gas that produces UV light, which the phosphor absorbs and converts into visible light.
I've never heard of a neon tube with starting heaters, so as far as I can tell, all neon tubes are cold cathode by default and the term is meaningless for them.