The family pool, installed in 1984, last had a bulb replacement done by a professional a couple years ago, which saw little usage before failing. Presumed it might simply be a bad bulb, but after personally removing it (shutting off the breaker; it's a low-voltage line), bringing it to the deck, and taking the bulb to test for continuity at the hardware store, the bulb proved not to be the problem. The in-deck junction box is incredibly corroded. Breaker is ok (the pump on the same line runs) and when flipping the light switch by the pool, a clicking sound is heard back where the pool equipment and transformers are.
I'm not familiar with what may need to be done other than a bit of research online, but presume a test for power at the the in-deck j-box is one step. There's a spa light that's out as well, which I thought I could test and if it was also not working with a good bulb, then we'd know the problem is upstream for both lights. Photos of the j-box attached - I'm not certain what I'm looking at, but it seems like 3 wires are running to the pool light (one is a ground?) and others out to the spa, but which are which, and which are the original power lines? The wingnuts are frozen, and some of the connections are done without wingnuts - just a glob of corroded metal with several wires fused to it. A mess.
All advice appreciated - I may have to back out of this challenge, and now, thinking of it, should have confirmed here first that if the transformers are bad, could this lead to full 120 coming through instead of 12V? I'm aware that I'd need to seal/putty up (underwater epoxy) the points where the conduit enters the pool and in-deck j-box, and add a new o-ring to the light and probably a new j-box gasket. Even if this job is too big and we completely give up now (we're just not interested in pool illumination enough to spend $600-1000 to have it done) does it still make sense to put on a new o-ring, new gasket, and putty all the openings back up to maybe prevent further damage? I can see there's moisture in the in-deck j-box though this might have come up from pulling on the light cables to remove the fixtures.