I have a chlorine generator for the pool, which came with the house, so it's probably at least 8 years old, if not older. It's been on the list of house electrics that probably should be coming to the end of useful life and replaced. Today, I noticed that the power LED wasn't coming on, but the LCD display was working, so that ruled out a power transformer issue. I was prepared to spend about $400 for a new system board and install, but checked the interwebs.

Five minutes of searching led to a pool forum and a thread that matched my problem with 33 pages of posts. Three posts from the top of the thread came the answer: A failing/failed variable resistor, and the name of an online vendor, and the part number! $6 including shipping. Then there were the install write up and a guy posted a YouTube video . . . now to dust off my Hakko soldering station.