Polish PNW-57 night vision goggles conversion

[Timothias]

Greetings!

I bought a set of nvg:s of the model PNW-57 as used military surplus. It's a tanker's helmet with attached goggles. I don't know much about electronics, and took them to a friend of mine who knows a lot, but my fault was not finding enough info on the product before taking it to him. There's a box in the back of the helmet that has a line attached to the goggles and a line that goes to the electric system of the tank. Just by looking at the thing (which was made decades ago) my friend thought that the box, which we opened and took out the insides, was a battery unit, so we cut off the line between it and the goggles and tried to attach the goggles to a power source. Nothing happened. After studying the thing more carefully we concluded that it was not a battery but some sort of converter (I'm not a native English speaker nor an electrician so here the terminology fails me), and the device is only to be used with a direct line connection to the tank.

Now, not having a tank and now having cut the line between the goggles and the converter I thought that maybe I could rebuild the converter with integrated batteries. Conversion options I found afterwards suggested that connecting a battery to that box on the back of the helmet would work, but with the severed wires it's an effort and quite frankly I'd like the battery to be inside the box as well if that's at all possible, because otherwise the thing will be cumbersome.

I found these two webpages with circuit pictures of the device:

https://www.circuitlab.com/circuit/dr2hde/pnw-57-switching-power-supply/
http://home.arcor.de/thuernagel/pnw57.html

I sent these to my friend and he asked if there is an explanation or a description on the "function of the coupling/connection". Well, there isn't. He also wondered what the VM3 in one of the pictures is.

Might there be someone on these forums who could make sense of these pictures? My friend said that it doesn't seem to be a difficult build, but we could use some info on how this thing might work... Also I'd like to hear if it can be done at home so that the result will be safe, because what I did understand from my friend looking at those circuits was that there will be quite a bit of voltage in that thing.

 

[KrisBlueNZ]

Hi Timothias and welcome to Electronics Point

This is way outside my experience but there are a few things I can tell you.

The first schematic is not a power supply; it's an oscillator based on a 555 timer IC. Its output connects to "VM3" which appears to be a voltmeter. I don't know what the purpose of this circuit would be.

The second page doesn't mean much to me because I don't speak German (or is it Polish?) but I can tell you a little bit about the schematic in Abb 6. It is a self-oscillating voltage booster using a transformer Tr and transistor KT. I can't tell you much about it because there are no component values, and no details on the transformer (the core type, number of turns for windings I, II and III, etc). The transistor is a PNP, quite possibly a germanium PNP such as an OC29, considering the age of this thing. The emitter arrow is not shown; it is on the diagonal line closest to the bottom of the diagram.

The secondary is rectified and smoothed in a "voltage doubler" circuit consisting of two capacitors, C1 and C2, and two diodes, K1 and K2. There is no information on these components, although K1 and K2 are probably some kind of tube device from before my time. Someone else will recognise them though, and this may give some clue as to the output voltage from the circuit. The output is DC, and comes out on a screened cable in the bottom right of the diagram.

The output voltage will be adjustable by R01 and R02 (potentiometers) and the strange-looking switch shown just below them.

Hopefully, someone else here will be able to give you a better description!

 

[Timothias]

Thank you for your reply! I'll forward this to my friend! Any info is helpful, and alternative ways to achieve the same thing this thing is doing would be fine too - historical accuracy went out the window when we opened the box and took the insides out This is a strange piece of equipment, I opened everything up, including the goggles themselves, and the night vision component itself is basically just a piece of blown glass with some stuff inside. Not to say I have seen any modern nvg:s' insides, but I didn't expect those glass bubbles. I just hope taking them out into daylight didn't ruin them, but I guess they have to be turned on for them to suffer from bright lighting.

Oh, and yes, it's Polish I know a Polish person here, but unfortunately there was no manual of any kind inside the box this thing came in, so no info there.

 

[KrisBlueNZ]

So the wire from the box to the goggles, is that a coaxial cable? An inner wire, with a layer of insulation around it, then a screen, then the outer insulation? I guess it just needs a low-current high-voltage DC supply, but I couldn't estimate the voltage.

Can you take some photos of the insides of the box? Something I could try to match up to the schematic?

 

[Timothias]

The cable is precisely as you describe!

I took a couple of pics of the box. This was inside the metal container in the back of the helmet. The black box itself I have not opened in fear of getting some Soviet WW2-era goo splashed around my kitchen, but the components in the two close-ups are readily visible:

 

[KrisBlueNZ]

Is that a USB plug on the end of that cable?

Just kidding. Can you open the box any further? I expect the high-voltage output components (two capacitors and two rectifiers) and the transformer will be inside the closed section. It's probably sealed for safety. But you'll need to get into it.

The cable to the goggles, did you cut that off close to the box? If so, it may not be difficult to reconnect the new end inside the box, after removing the existing short piece.

Edit: If it doesn't come apart any obvious way, you may need to use a hacksaw. If you do a tidy job and don't crack anything, you should be able to reseal it with hot melt glue later.

 

[Timothias]

Yes, we cut the line right next to the root, only I have no idea how to connect that kind of cable with all that insulation without screwing up the connection and resealing it well enough. But I think my friend can help with that.

Actually, now that I think of it, I think we did open the top plate of the box and only saw a couple of holes inside, which probably held the K1 and K2 in Abb. 6. A kind of white sticks they are, the K1 and K2, and in the box the helmet came in there are replacement pieces of those too. The baby sleeps in the room the box is in right now, I'll send pics once I get my hands on them. I don't know if the box itself can be opened without actually destroying it, I have to investigate. I'm just wondering what might be in there, the amount of stuff in the circuit diagrams would at a glance be somewhat equal to the stuff in the visible part of the box, though I must again say I'm not an electrician. And the box itself is heavy, I think that's why we conluded that it's a battery, and feels very solid: It feels more like there was clay or concrete in it than circuitry.

 

[KrisBlueNZ]

OK. The enclosed part of the box should house K1 and K2, and C1 and C2. I expect it will contain part or all of the transformer. The transformer core will be made from either iron or ferrite, and could be quite heavy.

I assume that section will also house the connection points for the cable, and you'll need to get access to them to reconnect the cable.

Reconnecting the cable is not difficult. Your friend should be able to do it easily.

 

[OLIVE2222]

Those googles looks fun to play with!
I find few information's on the web, mainly in polish unfortunately.

Here the way to connect the famous circular USB connector
http://russian-speznas.blogspot.be/2013/11/night-vision-device-pnw-57-converted-to.html

In this thread
http://www.elektroda.pl/rtvforum/viewtopic.php?p=3230751#3230751
a link to the manual here:
http://www.elektroda.pl/rtvforum/download.php?id=554646


And a high voltage supply generator link in this thread first post
http://www.elektroda.pl/rtvforum/viewtopic.php?p=9641808#9641808

Olivier