Over the past few years I have been slowly putting together a Franken-ebay stereo microscope. The stand, microscope, and ring light all came from different vendors and were mostly selected because the price was right. Adapting the stand to the microscope turned out to be a easy job on the lathe. The ring light fit off the bat (I did measure my scope before buying so not a surprise.). But I was left without a light source. Looking on ebay for a matching source they ran from $75 to $300 depending on condition.
Eventually I decided to just build my own. The official light sources typically use a halogen bulb. These are hot and have a useful life measured in the tens or hundreds of hours. Since I was building one from scratch I decided to go with a LED light source. This should result in a light that runs cooler and longer than a halogen bulb would.
Here are some progress videos I took during development of this light source: