so fast-forward a little, i now know more about xenon flash tubes and how they work, and there are currently two suspects in this case:
- the new lamp i used as replacement expects more than 250V to fire
- the 250V capacitor (a small film one, mind) could be bad
since the charge board is hard to take apart in order to replace the capacitor, i've instead sourced another bulb which seems to be more suitable for this application and it should be here in a few days
this time i'll record the process of replacing it for those curious