Good info about the AN/PVS-4 and it's big len brother, the AN/TVS-5 can be found here:
Wikipeida AN/PVS-4 / NVS-700 / SU-87 Page (yeah, it's known as all of those to the US)
I've spent the last year playing picking up parts and playing with various PVS4/TVS5 systems. Installing new parts, upgrading to Gen III, comparing reticle patterns, and learning about the devices and how they work.
The first thing to know about the PVS-4 (and all of my statements will always include the TVS-5 unless otherwise noted), and that it's super tough.
The PVS-4 was clearly designed to be stomped on or mistreated within reason. The parts don't break easily, but they can have their issues.
The PVS-4 is made of the following main components:
The <span style="font-weight: bold">Objective Lens</span> (95mm for a PVS-4, 155mm for a TVS-5)
The object lens contains three primary use components:
- The windage and elevation knobs (1/4 MOA)
- The reticle adjustment assembly / holder
- The reticle cover screw cap
- The reticle LED
- The reticle cell
One of the neatest features about the PVS-4 is that you can swap out the reticle cell for one that supports the mission at hand. I’ve run across: (M16/M203/M79) (M14/M60) (M2) (M72A1) (M67) (Forward Observer) (Bradley Stadia) (Israeli C4 7.62/5.56/RPG7) so far.
Interestingly, all the reticle cells are simply small pieces of material with lithographed patterns on them, embedded in a small metal tube.
The <span style="font-weight: bold">Battery Housing</span>, which comes in at least 3 flavors:
- Original: contains two proprietary BA-5367/U lithium battery housings, also, some of them have iridium “glow in the dark” paint to enable the operator to see the brightness control and reticle control.
- Variant 1: contains a single BA-5367/U battery slot for use with a single battery or a AA Battery Adapter (on top)
- Variant 2: contains an integrated AA battery assembly (in the right side)
Inside the battery housing are:
- The on/off/gain switch/varistor (potentiometer), which is used to turn the PVS-4 on or off, but also to turn up the power to the IIT (Image Intensifier Tube) which is another way to saying “turns up the gain.”
- The reticle brightness control varistor (potentiometer), which varies the amount of power supplied to a LED in the center of the objective lens, which in turn shines through the currently installed reticle cell.
- A 4 pin IIT connector that slides back and forth slightly because the IIT moves back and forth as part of the scope’s course focus adjustment
- Two resistors
- Several wires to connect the components together and attach to the battery assembly
- Mount point for weapon mounting hardware
- Rubber o-ring to seal the objective lense
- Power connector for objective lens reticle assembly
- Two metal backed rubber grommets for the varistors
<span style="font-weight: bold">The Eye Piece Assembly:</span>
The eye piece assembly on a PVS-4 is where the IIT (MX-9644UV or MX-11620) screw into. It also contains the course focus and a diopter adjustment. Most importantly, it also SHOULD contain TWO slip rings that hold the IIT in place to resist shock. This makes properly installing the IIT a pain in the ass.
If you are looking for compressive information on IIT’s, then you may want to go to this site:
Aussie site with complete OMNI tube breakdowns including MX-9644UV vs MX-11620 tubes
This is where I get a chuckle: when someone indicates that a Gen II and Gen III PVS don’t perform differently. Gen III PVS-4s have better S/N ratio, higher resolution, small halo, and hugely increased sensitivity. Now, some people will argue the fact, but “seeing is believing,” and I’ve been able to see a person at ~1500 meters with a Gen III TVS-5 under starlight… [LRFs are great…]
Eye piece assembly parts:
- MX-9644UV (Gen II) or MX-11620 (Gen III) IIT
- Metal base housing
- Course adjustment screw on ring WITH a gasket
- Rubber o-ring at base of the eye assembly between the diopter and main base
- (2) TWO split rings, used to hold the IIT in place during fire
- Eye piece optical assembly (multiple lenses and a diopter adjustment)
- TVS-5: 3 inch forward observer eye piece assembly ( an option, but something to behold as it truly makes a huge difference.)
The last part is attached to the PVS-4 (or TVS-5 when used as a weapon sight) eye piece and is called the <span style="font-weight: bold">Eye Guard</span>.
The eye guard prevents you from:
- Getting you eye too close to the [very hard] glass of the eye piece
- Has a shutter that opens when you put the optic to you face, which prevents spilling light as well as acting as a cushion
Some important things I’ve noticed about PVS-4 systems:
1) PVS-4s have seen a lot of use. Some are in great shape and some are not. They do tend to show up with dirt inside the lenses, and sometimes even inside the objective lenses. (Which are supposed to be sealed with some sort of toxic gas that prevents moisture from messing with the components.) The eye piece assemblies can suffer from similar issues when dirt gets into them, but they aren’t sealed units.
2) Keep up with the “dirt inside the lenses” concept: Sometimes it’s possible to have a PVS-4 with dirty lenses and think that you’ve got dead spots on/in the IIT. An internally clean PVS-4 is your friend… and it’s not always easy to achieve.
3) The “varistors” [the proper electronic name for it is a potentiometer, and varistor is short for “variable resistor”] in the PVS-4 are impossible to find once they break. Basically, at this point, it doesn’t appear you can find them. The good news is that they really don’t go bad all too often. The reason they are difficult to replace is that no really makes military grade sealed on/off/potentiometers anymore. ...and if they do, they don’t make them for the PVS-4 and publically available.
4) One of the biggest difficulties with the PVS-4 is installing the IIT tube properly. You MUST have both split rings around the tube while you screw it in, and it’s difficult to do. Companies that refurbish these units or build them from parts frequently don’t install them. So you want to watch out for that. Varo/Litton/Northrup Grumman/L3 didn’t put these in because they wanted to… (that’s at least the partial succession of owners of the original producer of the PVS-4 system).
I’ve got to move on to other things today, but I’ll correct this or add to it as people chime in or I remember other things.
Wikipeida AN/PVS-4 / NVS-700 / SU-87 Page (yeah, it's known as all of those to the US)
I've spent the last year playing picking up parts and playing with various PVS4/TVS5 systems. Installing new parts, upgrading to Gen III, comparing reticle patterns, and learning about the devices and how they work.
The first thing to know about the PVS-4 (and all of my statements will always include the TVS-5 unless otherwise noted), and that it's super tough.
The PVS-4 was clearly designed to be stomped on or mistreated within reason. The parts don't break easily, but they can have their issues.
The PVS-4 is made of the following main components:
The <span style="font-weight: bold">Objective Lens</span> (95mm for a PVS-4, 155mm for a TVS-5)
The object lens contains three primary use components:
- The windage and elevation knobs (1/4 MOA)
- The reticle adjustment assembly / holder
- The reticle cover screw cap
- The reticle LED
- The reticle cell
One of the neatest features about the PVS-4 is that you can swap out the reticle cell for one that supports the mission at hand. I’ve run across: (M16/M203/M79) (M14/M60) (M2) (M72A1) (M67) (Forward Observer) (Bradley Stadia) (Israeli C4 7.62/5.56/RPG7) so far.
Interestingly, all the reticle cells are simply small pieces of material with lithographed patterns on them, embedded in a small metal tube.
The <span style="font-weight: bold">Battery Housing</span>, which comes in at least 3 flavors:
- Original: contains two proprietary BA-5367/U lithium battery housings, also, some of them have iridium “glow in the dark” paint to enable the operator to see the brightness control and reticle control.
- Variant 1: contains a single BA-5367/U battery slot for use with a single battery or a AA Battery Adapter (on top)
- Variant 2: contains an integrated AA battery assembly (in the right side)
Inside the battery housing are:
- The on/off/gain switch/varistor (potentiometer), which is used to turn the PVS-4 on or off, but also to turn up the power to the IIT (Image Intensifier Tube) which is another way to saying “turns up the gain.”
- The reticle brightness control varistor (potentiometer), which varies the amount of power supplied to a LED in the center of the objective lens, which in turn shines through the currently installed reticle cell.
- A 4 pin IIT connector that slides back and forth slightly because the IIT moves back and forth as part of the scope’s course focus adjustment
- Two resistors
- Several wires to connect the components together and attach to the battery assembly
- Mount point for weapon mounting hardware
- Rubber o-ring to seal the objective lense
- Power connector for objective lens reticle assembly
- Two metal backed rubber grommets for the varistors
<span style="font-weight: bold">The Eye Piece Assembly:</span>
The eye piece assembly on a PVS-4 is where the IIT (MX-9644UV or MX-11620) screw into. It also contains the course focus and a diopter adjustment. Most importantly, it also SHOULD contain TWO slip rings that hold the IIT in place to resist shock. This makes properly installing the IIT a pain in the ass.
If you are looking for compressive information on IIT’s, then you may want to go to this site:
Aussie site with complete OMNI tube breakdowns including MX-9644UV vs MX-11620 tubes
This is where I get a chuckle: when someone indicates that a Gen II and Gen III PVS don’t perform differently. Gen III PVS-4s have better S/N ratio, higher resolution, small halo, and hugely increased sensitivity. Now, some people will argue the fact, but “seeing is believing,” and I’ve been able to see a person at ~1500 meters with a Gen III TVS-5 under starlight… [LRFs are great…]
Eye piece assembly parts:
- MX-9644UV (Gen II) or MX-11620 (Gen III) IIT
- Metal base housing
- Course adjustment screw on ring WITH a gasket
- Rubber o-ring at base of the eye assembly between the diopter and main base
- (2) TWO split rings, used to hold the IIT in place during fire
- Eye piece optical assembly (multiple lenses and a diopter adjustment)
- TVS-5: 3 inch forward observer eye piece assembly ( an option, but something to behold as it truly makes a huge difference.)
The last part is attached to the PVS-4 (or TVS-5 when used as a weapon sight) eye piece and is called the <span style="font-weight: bold">Eye Guard</span>.
The eye guard prevents you from:
- Getting you eye too close to the [very hard] glass of the eye piece
- Has a shutter that opens when you put the optic to you face, which prevents spilling light as well as acting as a cushion
Some important things I’ve noticed about PVS-4 systems:
1) PVS-4s have seen a lot of use. Some are in great shape and some are not. They do tend to show up with dirt inside the lenses, and sometimes even inside the objective lenses. (Which are supposed to be sealed with some sort of toxic gas that prevents moisture from messing with the components.) The eye piece assemblies can suffer from similar issues when dirt gets into them, but they aren’t sealed units.
2) Keep up with the “dirt inside the lenses” concept: Sometimes it’s possible to have a PVS-4 with dirty lenses and think that you’ve got dead spots on/in the IIT. An internally clean PVS-4 is your friend… and it’s not always easy to achieve.
3) The “varistors” [the proper electronic name for it is a potentiometer, and varistor is short for “variable resistor”] in the PVS-4 are impossible to find once they break. Basically, at this point, it doesn’t appear you can find them. The good news is that they really don’t go bad all too often. The reason they are difficult to replace is that no really makes military grade sealed on/off/potentiometers anymore. ...and if they do, they don’t make them for the PVS-4 and publically available.
4) One of the biggest difficulties with the PVS-4 is installing the IIT tube properly. You MUST have both split rings around the tube while you screw it in, and it’s difficult to do. Companies that refurbish these units or build them from parts frequently don’t install them. So you want to watch out for that. Varo/Litton/Northrup Grumman/L3 didn’t put these in because they wanted to… (that’s at least the partial succession of owners of the original producer of the PVS-4 system).
I’ve got to move on to other things today, but I’ll correct this or add to it as people chime in or I remember other things.
