So I have two PVS-14s both are ITT and were manufactured in 2012. They have been used in extreme conditions with a large number of hours of use.

What should I look out for to know when it's time to upgrade the tubes?

I've got an older OMNI IV from the late '90's with probably upwards of 1000 hours and I haven't been able to tell a decrease in performance as compared to newer ITT tubes I have.  I sold NVG's for a few years and was told by the individual I was working for that the tube would begin to clog up like a dirty air filter and not allow as much light through so to speak.

When your wallet and/or lipstick 6 will let you get the new filmless white phosphor.

if you can still see good at night, then they are good.


ETA: If you used them every single night for 4 hours each night for the past 5 years never missing a night you are still only at 7,300 hours of the 10k service life.

This would be my best guess; I'd think that the tubes image quality and performance slowly fades over time.  I'm not sure how the 10k hours is calculated that would be interesting to know.  Maybe 10k hours until one specs diminishes by 50%.

Pretty much this. If you know someone else with a newer/low hour tube then compare your gear to theirs that may give you an idea. FWIW I'm running gear from the 70's and 80's and its still fine. No idea how many hours on those tubes, but they certainly weren't "new" when I got them.

I agree with the first half of this. The 10K hours service life probably does not apply to me because of the abuse that I put on them. Still, overall, these tubes are pretty tough - and if they are still doing the job then I would keep them in service until the eventual upgrade. If you have scorches or haze then you can recondition the tube periodically with the "sock drawer" trick. I am currently due for this on account of a situation where I needed to observe a dirtbag for a long duration that was located in a shadow next to a lit area. The tube has some haze in it but it will recover.

Good stuff guys. Thanks a lot.

They are still pretty clear and blem free tubes I was just wondering. I have been caught out in the daylight a few times without caps on due to long ops and hunting trips.

The honeycomb are pretty visable in one tube was the reason I was asking.

Well the "honeycomb" is just part of the deal I suppose; it really doesn't affect anything; some are more noticeable than others.  That kind of stuff I don't even notice after a few hours.  It's the "fogging" or "hazing" that really degrades the view.  I had a -14 that was beat to hell and probably 5-10 years old.  But once I put new lenses on it, it still had a really nice picture.  Until my buddy left it on and printed a nice picture of his back wall on it.  So yeah, if you don't abuse it, it will last a long time.  And even if you do abuse it, it will still last a long time.  We are fortunate that we can buy replacement parts.  But with a little luck, you won't have to.

I have had omni VII tubes that customes wanted me to rebuild that had completely crapped out well before 1000 hours of use. By completely I mean that when tube was torn down to its individual parts both the power supply and the tube module tested and both had failed and the entire unit was basically a paper weight. I have also had omni IV tubes that had been put through so much abuse that they may as well have been dropped off a cliff and are still running perfectly. The expected life of a tube depends on the use and durabilty of the tube. However, the operational life of a Tube ultimately depends on the effective half-life of the phosphor used on the input side of the output screen. This is assumng that the tube hasnt been abused and hasnt recieved damage of any type other than natural wear and tear. When a tubes phosphor hs reached the end of its effective half life the image will slowly dim, which is also why tritium sights are bright until the tritiums half life is passed after which the tritium will slowly dim out for example.

Also if the tubes vacuum is compromised in any way and atmosheric gasses make there way into the tube it will cause the image to look like if you were peering into a glass of green carbonated liquid that had just been shaken up and bubbles going crazy within the liquid. This is what a tube looks like while it can stoll operate but is going to air. The atmospheric gases that are making their way inside the tube interfere with linear path of the electrons and theyvare unable to then form a usable image that a tube operating normally would be able to produce. Eventually photocathode poisoning will take place and the tube will be dead. 

Those reasons along with some others are deffinite cause for tube replacement. But as stated in an earlier post, if you can see in dark conditions with little to no amnbient light sources other than starlight then your tubes will likely be usable for quite some time.

Sounds like you are describing what is known as fixed pattern noise which is something that can be seen in all tubes if the light levels are high enough. This doesnt indicate damage or that anything is wrong with your tube. What it does mean is that you are in an environment having higher than normal levels of light. Fixed pattern noise shows up as a honey comb or chicken wire like structure that is spread uniformly accross the entire FOV and will become less visible and will eventually disappear as light levels become less and less. If the chicken wire structure is localized to a particular area within the image and is visible in all light levels then you have what is considered to be a cosmetic blemish or defect in the image. It isnt a sign of tube damage and doesnt call for tube replacement. you may decide to replace the tube if you really cant get past the blemish for one reason or another and you decide to get rid of it and get a new tube because you cant live with the blemish in an otherwise fully functional tube and prefer to replace with a tube having an image that is clean.

You need to upgrade when you are no longer happy with the performance or when you want to move to filmless or white phosphor.

Other wise if they work for you they work for you