Image-intensifier tube care.

A tube ages two ways

Image-intensifier tubes wear with operating hours and they wear with light insult. The first is unavoidable: every hour of use moves the tube along its service life. The second is largely self-inflicted. Bright sources, daylight exposure and careless bench handling take hours off a tube that the mission never used. Gain fades gradually, so the damage rarely announces itself; the device just becomes quietly worse than the one beside it.

Light discipline, on or off

Intense light is the fastest way to shorten tube life, and a powered-down device is not immune. Caps stay on whenever the device is not in use. Storage is closed and dark: an opaque case, not a shelf. Avoid pointing the objective at the sun, floodlights or vehicle headlights, and treat lasers as a hard no. A device left uncapped on a bench near a window is being damaged while it sits still.

Know your blemishes

Most tubes carry some cosmetic blemishes within specification. What matters is change. Record a baseline: view a plain, evenly lit scene through the device and note the position and size of any spots when the device is issued. Repeat the check on a schedule. New dark spots, growing spots or honeycomb patterning are signals worth escalating before they become failures on task.

Handle it like optics

Drops and knocks damage tubes and knock optics out of alignment, and the housing hides the evidence. Mount and dismount over soft ground or a bench, not concrete. Keep fingers off glass. Clean lenses with a blower and lens tissue, never a sleeve, and keep solvents away from coated surfaces. If the device took a hard knock, function-check it before it goes back in the rack.

Storage preserves gain

Between tasks the rules are simple: dry, dark, batteries out for long-term stowage, stable temperature, and nothing pressing on or rattling against the optics. An exact-fit hard case does most of that by default, which is the reasoning behind the NODBOX for the AN/PVS-31A and 31C: the device sits still, capped, in the dark, in its own moulded space. Our storage guide covers the full routine.

Quick checklist

• Caps on whenever the device is not in use
• Stored closed, dark and dry, never loose on a bench
• Blemish baseline recorded at issue, rechecked on schedule
• No bright sources through the objective, powered or not
• Lens cleaning with blower and tissue only
• Function check after any hard knock