12v AC Colorlogic pool light drop-in replacement resolution

I think that's a great find @willerd - thanks very much for posting. If my area is any sign, there seems to be a vast number of ten-year-old to thirty-year-old 10" luminaires that have become so decrepit they are hardly worth trying to repair or salvage. From bulb sockets that deteriorate due to age and/or water intrusion, to outer mounting rings and gaskets that become nearly unusable (and tough to find gaskets), plastic outer rings that get brittle & break, etc., the need for quality, UL/ETL certified replacements is apparent and the prices seem rather unreasonable. I guess it's tough for folks to make the transition from "I need a lightbulb' to paying a tech $1800 to replace the luminaire with a $1200 J&J XG-W series or similar from a pool store. And the struggle, as you say, to research all the options in between. One of my neighbors had an electrician install one of those amazonian ~$200 ("no-go" as you say) RGB lights. It works, but I think his and many of those use a 3-wire or 4-wire proprietary cord (I'm guessing RGB+Common) that has to be pulled all the way through the Jbox and back to the equipment pad (sometimes 150-200 feet), and replaces the pool rated 12V transformer with a new hermitically sealed control transformer - with no apparent markings or even claims for ETC/UL certs, no claims about isolated windings either. Add to all that our bad luck with the longevity claims of most LED's, and with reviews pointing to same, it's tough to make a replacement decision.

Maybe another option is a new Pentair Amerlite luminaire for $400 or $500 (or similar for $900) that supports a standard A19 socket running 12VAC. Then a $60 white LED bulb or a $150 colorsplash RGB controllable bulb (or cheaper knockoff). At least with the A19 socket the bulbs are replaceable. Per some of the aforementioned reviews and my own experience with a wide variety of LED's around the house, I feel lucky if I ever get 10,000 hours out of one, versus the claims of 20,000 or even 50,000 hours. For any solution it makes sense to me to add the $15 4 year protection plan if offered. Or buy such a plan elsewhere.

One advantage of the fixtures that support standard 12V cords with three wires, (your new Pureline PL5845 for $329 from InYopools or that $1200 J&J poolstore option or the new amerlite fixuture) is that you should be able to simply cut the old cord and attach the new cord to the old one and pull it the 5-10 feet to the first junction box.

Regardless of the install, whether using 12V or 120V fixtures, whether or not one is using a pool rated transformer with isolated primary and secondary, I urge folks to make sure the primary circuit is on a GFCI breaker (if not, replace with GFCI breaker). That's admittedly controversial for 12VAC implementations, but there are rare cases of errant wiring in old pool-rated transformer enclosures that eventually shorted primary to secondary, resulting in death. Rusted ground wire falling off, wire nuts falling off, or other bad practices and lackluster maintenance can lead to all sorts of havoc down the road.

Good luck with your PL5845!!