From G3PLX:
Marek:
That's interesting about the tape. I cannot picture exactly what you have
there, but it's well-known that some materials will degrade (e.g. lose
colour) quickly when exposed to UV, so you may be able to see that coloured
tapes in some parts of the coil enclosure have become faded, and in other
parts they have not, and you should be able to relate this to whether there
is a line-of-sight from the places where the tape is located to the places
where the corona is likely. Especially if there are some places where there
is one layer or tape partly over another, it should be possible to deduce
from the pattern of fading that the outer layer has been exposed to UV and
the inner layer has not.
John's suggestion to look or hear (or smell) the corona, is also a good
idea, but then we need also to ask the experts if it's true that there is
always UV radiation associated with corona. I don't know enough about it
myself.
73
Peter
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