*We use the following testers:
*Dan Nelson calibrated TV-7D/U with sweep tube adapters, & digital meter with plate current test at 150V.
*Paul Hart calibrated/modified Westmore 501 (Triplett 3444)
* B&K 747B calibrated
Test results will differ between various testers for many reasons such as technical design, aging components, etc. So while test results are a good indication of quality there can be some difference between the many differently designed & maintained testers.