[codefox1]

Time Out! A tube tester can try to heat up the filament, check for shorts within elements, do a rough check of cathode-plate effieiency at diminshed voltages as a erzatz rectifier, and perhaps indicate or point to other anomolies of the grids or overall polution of the assumed "perfect" vacuum.

Did you ever hear the difference in a tired old AA5 when a much better 50XX was subbed? I did.