I'm a pack rat. I don't save everything but if I think it might be useful it gets buried in some place that I often forget.
This week I was adding some bi-color LEDS to my railroad. I kept forgetting which way a switch was set (a turnout and the DC power gets reversed depending on the tracks entering the area) so I decided to add the LEDs. If it's green the power is one way and if it's red the reverse. Since there are three tracks entering the area I know that A is green so B and or C must be green (or red and red). The turnout direction shows with a fourth LED.
But that's not the point. The LEDS work as planned. But in the process something happened to the lights that illuminate the scene.
With me so far?
Troubleshooting time. THe best I can determine is the power supply was dead. 12 volt DC. Sigh. But wait a minute! Under the bandsaw I have a couple of spare PC power supplies from old computers. But did they work?
The answer is yes IF I can determine how to turn them on. Some power supplies are turned on by hooking a green wire to a black wire- I hope. Yep. One power supply fan cut on. I checked the yellow and black wires and there was 12 volt DC. Hooked up the lights and voila! Light!
THe other older power supply was more problematic. No green wire. I built a test device and found the leads. Not quite 12 volts but for lights, sufficient. So I have to power supplies that have been around for way too many years. But the price was right.