PVS-4 needs help

Discussion about Night Vision Weapon Sights

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PVS-4 needs help

Postby fletcher969 » Tue Dec 03, 2013 3:12 pm

Hi all.

I've got an old PVS-4 with some issues. It sat around unused for over 10 years while my father had it, but I'm the new caretaker, and I'd like to get it working.

First issue: the image is EXTREMELY dark and grainy. So dark in fact that when I first turned it on in a semi-dark setting (some ambient light filtering inside from an outside pole light), I thought it wasn't working at all. When I tried it in a lighted environment (45W bulb) with the cover off, I could see an image, but it was extremely grainy...like I would see things if I were legally blind. Pretty much the same thing in daylight with the cover on and adjusted appropriately. I took a few measurements.

Scope body terminals:
Measuring from terminal 1, I saw 2.7v on terminals 2 & 3, and 3v on terminal 4.
I measured no ohms between terminals 1 & 4, and 200 on the 1K setting between 1 & 2, and 1& 3.
Not sure if continuity is important, but I saw 2-way continuity between 2 & 3, and 1-way continuity from 4 to 1.

I saw 2-way continuity between terminals 3 &4, but no others.

Second issue: the reticle doesn't work. I don't know how to measure the the circuit, but I did remove the LED, and hooked up 2.6v directly, and it works, so something is open somewhere.

Any suggestions or opinions regarding this scope?

Here are a couple of pics of the tube:

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Joined: Fri Aug 24, 2012 8:51 am

Re: PVS-4 needs help

Postby mugur » Tue Dec 03, 2013 3:32 pm

i've had exactly that tube but was NOS. pins 2 and 3 are the gain control, but mine was fully lit when just powered the tube to the pins 1-4 (no potentiometer to the gain pins). So basically if you apply 3V (like i did) to the tube should light up a perfect green image. Your tube looks like it's experiencing a power failure or just got vented (vacuum lost). Just unsolder the pins 2 and 3 to be totally sure is not the gain control in any way.

Maybe some of the wise guys will jump in to help you more.
Quality only hurts once!
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Joined: Fri Nov 11, 2011 11:40 am
Location: Romania

Re: PVS-4 needs help

Postby fletcher969 » Wed Dec 04, 2013 5:20 pm

I removed posts 2 and 3 from the tube, and the image got noticeably worse, becoming darker, and less focused (as if that was possible). I literally had to point it at the aforementioned 45W bulb with the lens cover off to see anything. The light was apparent, but if I didn't kow it was a light, I'd not have been able to identify it.

Not sure if that's any indication or not, but removing gain from the process definitely makes it worse.
Posts: 13
Joined: Fri Aug 24, 2012 8:51 am

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