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Posted: 8/10/2019 11:49:26 PM EDT
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
Link Posted: 8/11/2019 12:17:50 AM EDT
[Last Edit: 8/11/2019 12:20:14 AM EDT by MunnyShot]
I'm sure TNVCSam will be along shortly for thing to check.
Link Posted: 8/11/2019 1:45:06 AM EDT
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
Link Posted: 8/11/2019 3:16:08 AM EDT
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.
Link Posted: 8/11/2019 3:36:40 AM EDT
[Last Edit: 8/11/2019 3:42:04 AM EDT by NSFJojo]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By txdx:
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.
View Quote
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.
Link Posted: 8/11/2019 4:23:03 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By NSFJojo:

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.
View Quote
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
Link Posted: 8/11/2019 9:07:51 AM EDT
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.
Link Posted: 8/11/2019 9:56:00 AM EDT
Link Posted: 8/11/2019 10:51:31 AM EDT
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.
Link Posted: 8/11/2019 11:37:00 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TNVC_Sam:
More than likely not a lock ring issue unless you can hear a back and fourth rattle if you shake the tube up an down.

I am betting its a bent contact issue. The metal prong contacts on the battery compartment can wear out over time and just make intermittent contact with the tube which is why it'll sometimes power up and randomly shut off. Its an easy fix but again I would recommed a pro do it if you havent assembled a -14 before and just so you get a dry nitrogen purge....in before the bubba tool shed builders say canned air is just as good.

I can normally perform the fix in less than 20 min but alas I am currently full time with the Air Force in San Antonio going through training and will be for many months.

jacob@tnvc.com is the man to contact as he can perform the Troubleshooting and repair.

-Sam
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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?
Link Posted: 8/11/2019 11:51:46 AM EDT
Link Posted: 8/11/2019 12:15:18 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TNVC_Sam:
That is a dead ringer for a contact issue as the compartment is still good because the IR light fires up, super easy fix no need to even replace the part, a quick bend of the contacts will have her back up and running.
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Cool! Thanks for the input. Are these contacts the two inside the main housing under the intensifier (upper housing pins?)?
Link Posted: 8/11/2019 2:50:26 PM EDT
Link Posted: 8/11/2019 2:58:46 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By TNVC_Sam:

yup the gold colored ones that look like a dwarfs T-rex's hand with carpel tunnel syndrome
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Thanks man
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