My suggestion about UV was based on your description of the symptoms, and it
sounds as if you agree with this, but I think it would be most useful if,
before you modify the installation to remove the problem, you take some
steps to make a positive verification that there is UV radiation. You have
said it's not enough to show on a banknote. If you do not make a POSITIVE
test for UV, it will be possible to make a wrong conclusion, and this could
be important for the future.
Does anyone know of a way to test for UV exposure? As Rik says, it's the
total dose that will give the burning, so maybe what is needed is a
scientific way to measure UV dose. How do they check UV sunbeds? Maybe
there is some way the experts can test that UV suntan beds are safe to use,
and you could contact these people and see if they can tell you how to check
One idea that occurs to me (because I have the equipment here to try it
myself) is to see if an EPROM is erased near to the possible UV source, and
make some tests to see how long it takes to erase it compared to exposure to
a known intensity UV lamp. But maybe it takes too long. I know it takes a
long time to erase an EPROM with sunlight.
In the meantime you can protect yourself from the UV simply by hiding the
coil behind an opaque sheet.