I appreciate your response below. I need to determine if my CR70 is working properly before I can trust the results from it. I will print and keep your advice. Thank you.
On edit: I did try this with the 16EP4 and the needle pegs when you turn up the cutoff set. It is nearly impossible to set it in the range as the needle jumps.
On the emissions setting, the cutoff set knob takes the needle up rather fast and not particularly smooth, but it stops in the middle of the good scale and goes no higher.
Quote:
Originally Posted by miniman82
16EP4 is a metal cone tube, I bet it's gassy. Easy way to tell with the CR-70 is start with the cutoff knob all the way counterclockwise, flip the switch to read emission, then slowly advance the cutoff knob till it does something. If the needle slowly rises and you can control it like normal, the tube is probably good (able to display a picture anyway). If however at some point the needle pegs full scale while advancing the cutoff knob, you have a gassy tube. This is called out specifically in some B&K manuals, but not in the Sencore one. B&K call it 'gas regulator' action, whereby the gas inside breaks down at some voltage allowing full conduction at that point. If that's what you're seeing, I'm sorry but the tube is shot.
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