I'm sharing this post for the benefit of anyone with a faulty Sunray flourescent light fixture. The Sunray units from STP Distributing are fitted standard to many FR products.
These twelve volt fluoro units don't use replacable starters and ballasts like traditional home fluoro units, instead they have an electronic circuit board that connects inside the light between the 12v trailer supply and the batten holders.
It is very common for these ballasts to stop working. Generally they overheat and one or more components on the circuit board burn out, resulting in the unit not lighting up. In the Sunray units there are two power diodes that commonly fail as they are under-rated for the wattage they have to drop.
When this happened to mine, my first instrinct was to simply replace the whole unit, but I was surprised to see how expensive these units were new, so I went looking for other options.
I came across a web site by SunrayTS that sells these electronic circuit boards as direct replacement parts for about $22 each (well under half the price of a new unit).
The web address is www.sunrayts.com
Replacement of the circuit board takes about 45 minutes and requires drilling out some soft aluminum rivets. The job is not for beginners, but is certainly a handyman (handyperson)-level task. There are instructions and diagrams on the sunrayts site.
I've noticed that the replacement boards have a new heat sink assembly that should prevent the failures seen on the original boards.
If anyone would like detailed repair instructions, I'd be happy to post...