I see you have one on the way.
The most important things on a CRT checker are getting ALL paperwork ( set-up guide, manual & schematic), & a good assortment of adapters. Sencore also
had a universal adapter that tests almost any CRT if you learn how.
They were very reliable as a rule. The main CRT cables on Sencores failed
on all 3 of ours but thats with HEAVY use. The commonly used adapters
also were troubled. Last thing is get a MODERN checker from apx 1970's up.
As for brands either B&K or Sencore is the way to go IMHO. We used the
Sencores most but has a few B&K's also.
73 Zeno
LFOD !