A simple positron annihilation lifetime (PAL) spectrometer using secondary electrons as the starting signal has been constructed inside the existing slow positron beam at the University of Missouri-Kansas City (UMKC). This instrument has been employed for investigating photo-degradation of amine-cured epoxy coatings exposed to UV radiation. The lifetime results are compared with the S-parameter changes obtained from positron annihilation spectroscopy (PAS). A significant decrease of the S-parameter and of ortho-positronium (o-Ps) intensity in polymers is observed as a function of exposure time and of depth from the bulk to the surface. This is interpreted as due to a loss of free volume and holes resulting from photo-degradation in the samples. UV irradiation in epoxy produces a "dead layer" near the surface up to a thickness of 0.3 mum, where a substantial change in the o-Ps intensity and the S-parameter is observed.