Was this made in the mid 90s? If so, I was working as a product/test engineer at the plant where this was likely made. Unfortunately, I was not assigned to this product line but Tek supplies were made in the plant, although this one does not look familiar (and its been ~30yrs ago).
In general, Zytec used a lot of Unitrode switching regulator ICs in that era. Looks like your bad parts are all on the AC input rectifier/filter/primary side of the SMPS. There may be a power factor correction circuit there as well.