Frank Skomial , Sep 29, 2012; 03:02 a.m.
When I was prototyping strobe designs, and drove flash tubes to destrution on purpose, either by applying too much energy, or by applying too high voltage, eventually some flash tubes at the end of life experienced longer light decay, ... perhaps what you call afterglow ? In most cases, near the end of tube life, the light intensity outut dropped drastically, and sometimes instantly. (excluding extreme loading that blows the tube instantly)
If I understant what your aftergow means, perhaps you just need to replace the flash tube (xenon bulb), if flash works otherwise. Other flash electronic components, (except a thyristor if there is one), should not cause the flash tube to glow longer, as it would be more of abrupt failure.
I would try flash bulb replacement first.
I do not know Norman 200. However, if the flash output variation is done by a thyristor (case when flash light duration decreeeses with smaller energy fraction setting), and you use partial power setting controlled by the thyrisor, other than tube components could be responsible, e.g the thyristor not shutting down fast enough.
Does the afterglow happens at full power discharge, or at fractional ratio setting ?