I just got these and think that the owner changed the tubes. There are supposed to be autogated. no sound when turned on.

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These are my first set, I was under the impression that autogated meant the woosh sound.

I may be wrong. I will contact Night Optics and see if they can ID the tube.

What does the tube say on it exactly? Autogating is not so much a "woosh" sound as much as an electric whine, like a camera flash capacitor recharging.

And keep in mind, it's not always within the spectrum of human hearing.

I found the easiest way was to look at a streetlight, preferably one 50-75 yards away. If it auto-darkens you're good, if not you need a shoebox and 24 hours.

if you look at a brighter area then the ABC will cut the brightness of a standard tube - with an autogated one it will be so fast to change you proberbly
will not see the change , but with some standard tubes the ABC is not noticable either -  some gated tubes are quiet and in the housing you might not hear the whine, there is
a way to tell by lowering the tube voltage till the gating slows so you can see it and on utube there is a video -   https://www.youtube.com/watch?v=2ike1VsbI7o

thanks for all the input guys.

Well the good thing is that there is no blemish on the tube.

They look nice and clear.

They are third gen. Gated or not they should do what i need them to do when I need them.

Better than no NV at all.

Night Optics tech said I was good and tube was legit.

thanks again.