I would guess this term is misapplied.. lots. I have bought / for good money / tubes that were barely servicable.(referred to as 'nos') One look at the marks on the pins makes me suspicious.I'm refering to power tubes. These have a shorter life / and some amps are harder on power tubes than other amps.I have the CJ 5's,and they allow bias for each tube individually.(all 16)This method is a pretty good "tube tester" unto itself.Paying big bucks to an individual is risky.I've seen used tube testers here for sale for around 500 bucks... Being in possession of such a tester does not an expert make. From everything I read Ram Labs & Upscale Audio do many tests most others don't do. Know your seller,be careful, and "good luck".
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