To resolve the problem of the lamp (cold cathode) not lighting up completely, i. e. at the tube's corners only: Place the palm of your hand over the tube when switching the scanner on.

For some reasons this will remedy the issue, but it is restricted to the outdated model 3600 and should be expected to fail with others respectively more recent ones. It should hence be unnecessary to open the case as some users have written elsewhere.

That trick was told me today by a most kind hotline employee of Plustek Germany who regretted to be unable to explain the phenomenon.

Obviously, this method will not work with a physically broken tube.