What is this bulb?

[Soi disant]

The problem with marine lamps is that anything to do with boats is stupidly priced.

Some thoughts:

A closeup of the end of a dimpled lamp someone was selling showed a small unthreaded hole. It is possible that the screws in the light would cut a thread into it, in which case some slightly longer screws and some washers to pack the length out might be an answer.

The lamp shown by snowhead is described as having a diameter of 12.6mm. If they mean this


rather than the cap, then that would make maximusi's caps larger, and it is possible that they would slide over the ends of the one in the photo.

In a world where the full panoply of gods smiled on him, and all the planets were in alignment, the caps from his old lamps would be a tight fit (so no soldering needed) and would bring the length up to 47mm.

In his shoes I'd be tempted to get one and try....

 

[Lucien Nunes]

The driver is a constant-current driver but the lamps are in parallel and have ballast resistors inside, a configuration that would normally be used with a constant-voltage driver. What this means in practice is that you are going to have to change the driver if you change the lamps, as they will have been specifically matched together. I.e. they have cheated things so that when the current of the driver is divided by that number of lamps, the voltage developed across the ballast resistors makes the lamp voltage right. The driver is only a very low output unit (3w) anyway.

I suspect the lamps have been made up specially for this range of fittings. What you might have to do is dismantle them and attach the endcaps to normal festoon lamps of suitable length and power. Then, substitute a constant-voltage driver of the same voltage as the festoon lamps, and equal or greater wattage rating to the sum of the lamp wattages.