I finally joined up to contribute my little project. I've done a lot of reading and learning on this forum. Maybe this information will help someone else. I hope this is the right place for this post. It's not exactly a flashlight mod, and it's quite simple.
I've been looking into making a joule thief type light for my wife to use while taking notes at night. A joule thief was appealing because 1) low light level, 2) good runtime, and 3) puts my garbage "heavy duty" batteries to good use. There are lots of sites that describe how to make a joule thief and one site that even shows how to fit it into the base of a PR2 bulb.
While looking into purchasing the components, I found a posting which suggested dismantling a cheap 1xAA or 1xAAA light driving a white 5mm led. I quickly found out that this wasn't as common as the 3xAAA setups you see everywhere.
Just this week I stumbled across a flashlight utilizing a 1.5V LED bulb in a PR2 base! Finding the PR2 bulb was great because it's much bigger and easier to work with-- my soldering skills are not that great. This gave me the idea to build it into a desktop lamp instead of a flashlight. It's actually more convenient to use than a flashlight. I took a retired halogen desk lamp (bulb costs as much as a new lamp), wired up a 1AA battery holder and the PR2 bulb. The halogen bulb can be seen at the bottom of the first pic. I soldered two metal pins (actually cut legs from a 5MM LED) and stuck it in. Here's the result:
Completed Project: http://tinypic.com/r/2vtxj4w/5
Close up of the bulb: http://tinypic.com/r/4ugx2v/5
Light in use: http://tinypic.com/r/2emd7dl/5
Total cost: $0.50 battery holder, $2.50 sacrificial flashlight, dead desktop lamp.
I used some Scotch tape over the glass lens to diffuse the light (removed for the bulb picture above). That's a trick I learned from this website! The amount and quality of light produced is just about perfect. I'm not sure how long this will run for since I just finished the project last night. The packaging on the said 40 hours runtime, but that was with the "heavy duty" Eveready D cell that came with the light.