Posted 20/06/16 by Tom J. Venator/Katface:

LED Salon lights for Katface (Swan 46 Mk I #62)

Katface has a lot of older Hella ceiling lights. All of the ones I have looked at have cracking in the plastic base and have showed signs of shorting and heating at the power wire connection. These are corroded and feel like solid wire. Conjecture is that minor shorting has caused some local heating. The lights are also 145mm in diameter so there was no direct replacement for them. Here is a picture of the old light that sort of shows the power connection.

While trying to fix one of these lights, without removing the power, I managed to get the dimming function to fail before the breaker flipped. At this point the only way to turn off the lights was at the breaker panel. Replacing the potentiometer at the nav station desk did not solve this problem. I then spent way too many hours searching for the dimmer. After a hint from Mr. Strom I found I have four of them behind the breaker panel mounted on the bulkhead to the aft head. Here is a picture in there. The top one is the one for the salon lights, the next one down is connected to lamps on the forward salon bulkhead and I have not figured out yet what the other two do. If anyone knows I would be interested.

As I was bemoaning my mistake in shorting out a difficult to obtain part it occurred to me that this could be an opportunity. I wanted LED lighting in the cabin anyway and this big heat sink implied a power user so perhaps I could jump to a new unit to drive LEDs.

Internet research drove me to call up LEDSupply. They were great and basically told me what to buy and then made sure I got the order correct. I ended up ordering 6 high power, CREE LEDs (2 spares), heat sinks, the LED driver and heat sink epoxy. Total cost around $80. LEDs use constant current which is the reason there is more than just the the LED in the replacement bulb one buys. Here is a picture of the LEDs mounted on the heat sinks and another of the driver next to the old dimmer for comparison.

I broke the bottoms out of the old Hella lights and reattached the wood trim rings to the underside of the deck with adhesive backed Velcro. Brackets may still be required if the adhesive does not stand the test of time. Soldered on leads and then put new connectors on the power wires. The heat sinks were screwed down with #4 wood screws and everything wired up in series instead of parallel so that all four diodes see the same current. I decided to keep the return yellow/green wire from the lights separate and only connect it to the LED – side of the driver but don’t know if that was strictly necessary. I bought the pot LEDSupply recommended but used the old one. It is sensitive but works. Here is a picture of one of the lights in the middle of the circuit. You don’t tie into the ground wire until the last one so I just left them on the old connector and taped it off to keep it from grounding on something else. Amazingly it all worked the first time and these single CREE LEDs are quit a bit brighter on full than either the replacement LED bulbs or the originals. How well they stand up to life on board is still an unknown but power consumption should be quite a bit less. At least I don’t have any more old broken plastic supports.