I have a filmless L3 white phosphor PVS14 which continues to exhibit some issues which I have observed extensively in the hopes someone here with build experience can solve. The symptoms I am experiencing are the inability for the unit to 'turn on' when rotating the switch to the on position, as well as flickering of the image which typically will result in total loss of the image. I experience these symptoms only occasionally, and each time the unit has eventually returned to normal operation for extended periods of time in between presenting these no-image or image flickering symptoms. The unit IS on a TNVC N-PBM bridge primarily though I have experienced the issues when the unit was not connected to the bridge one time. Symptoms have appeared even with an unused Energizer lithium battery.

Here are my observations which should help in the problem solving:

1) No obvious signs of problems in the battery compartment, battery cap, etc like leakage or abnormal cap spring, etc.
2) Cannot replicate the symptoms by turning the battery cap slightly, tapping on the battery cap or compartment
3) there is no obvious "play" in the operation (on/off/IR) knob indicating it might be loose or something
4) Even when the unit isn't presenting an image or won't "turn on," I still get a red indicator light by turning it to the on-board IR setting, indicating that the battery doesn't seem to be the issue.
5) Turning the diopter adjustment ring on the ocular lens assembly when the unit is not powering on can return it to normal function, and once it has turned on, continuing to turn the diopter doesn't seem to cause any issues I'm pretty sure this has worked every time I've consciously tried it, but can't be certain.

I am no expert with the detailed technical issues but it seems less likely to be a battery contact issue based on my observations and I am making an uneducated guess that the tube retaining/lock ring is causing issues.

Somebody smarter tell me what to test or what might be wrong. @cj7hawk @txdx @NSFJoJo @TNVC_Sam

Thanks to all

I'm sure TNVCSam will be along shortly for thing to check.

maybe the lock ring inside your housing is loose? causing the intensifier tube to slide back and forth, losing contact with the electrical contacts. then when you turn the focus it pushes the tube back into position so it works for a while? Does it also go out of focus a lot?

only reason I suspect this is because I was playing around with some "soon to be demilled" no longer milspec parts, and I put a monocular together without the lock ring. it worked fine until it was moved at all, then the focus would be out of whack or the tube would just flicker off. The intensifier tube was sliding around inside the housing cuz that lock ring was not there to hold it in place. but when I would turn the objective lens focus in all the way, it would push the tube back in position and it would turn back on. Until it moved again.

I'm no expert but my job has allowed me to play with plenty of NV parts

Definitely a lock ring issue that allows the tube to shift around. Lock ring may be installed but the tube may have been inadvertently installed such that the clocking pin on the housing did not engage the notch on the tube itself.

Came to post this. Had the same issue in a unit last month. Locking ring: btfo.

just use a lock ring wrench from harbor freight, file it down to fit and crank that fucker up.

not sure I'd crank it down so much. I've seen the outer lock rings get stripped from over torqueing them. Definitely snug it up but maybe look into some kind of locktite to keep it secure

While you have the unit disassembled, wipe down the contacts with a bit of vinegar on a q-tip then with distilled water and finally an alcohol pad. Let it dry. There could be a bit of corrosion built up. It doesnt take much corrosion to mess with the points of contact.

I have not noticed any noise or feeling of the tube shifting in the housing but now that it's been mentioned I will check for it because it might be very minor. Also I haven't noticed a focus issue either although again if it's really minor I probably haven't really been "looking" for it so to speak.

When the unit isn’t presenting an image I am still able to get the red “IR on” indicator in the tube when I switch it that setting - would that indicate that the battery contact is still good? Or are we talking about multiple contact points where one to the tube could be bent/dirty and one to an IR light could be ok?

Cool! Thanks for the input. Are these contacts the two inside the main housing under the intensifier (upper housing pins?)?

Thanks man

Just to bump this in case anyone in the future sees this thread searching for answers to similar issues - I'm pretty sure fiddling (bending) the little pairs of gold contacts on the board fixed the issue. The problem is that the issue was very itermittent and kind of difficult to recreate, so I don't have a great sense yet for if I actually fixed it or not, but previously if I turned diopter adjustment or objective focus, sometimes that seemed like it would either trigger/fix the issue, and after bending those contacts a little bit I powered back up and turned each end numerous times through the whole range without issue.

I'd say it's pretty safe to say it's fixed. Took about 2 minutes. It's also possible that my four housing screws were backed out juuuuust far enough that it might have been affecting the contacts touching the tube in some situations - I say this because the screws backed out way too easy for my liking when I went to separate the board from the housing. I know they aren't supposed to be overtightened but they were not in there very far at all. I put them back in a little more snug without really cranking them down.

Cheers to Sam at TNVC.