TVS-2B Night Vision Scope MX-7794B

Crew Served Weapon Night Sight

© Brooke Clarke 2005 - 2008

This is a Vietnam era Crew Served Weapon Night Vision Device.  It uses a Schmidt-Cassegrain optical system.  The manual says 7 power.  The objective diameter is probably 5.5 to 6 inches.

Image Intensifier

Oscillator

Focus

Lens Cap - Filter

Reticule

The switch with the pointer has 3 positions.  CCW is OFF, then scope ON, then Scope and Reticule ON.
The large knob controls objective focus and the eyepiece controls focusing on the image intensifier tube output window.
When looking up at the stars at night there's a much larger number of start visible than with the naked eye.  Also there is no night adaptation of the eye needed since the scope has a bright output.  But you probably can see fainter stars with night adapted eyes.  The output color is green to match the peak in a human eye's spectral response.

This scope was not intended to be hand held, and doing so is very difficult.  Need to figure out a way to get it mounted on a tripod.

Upon receipt the unit appeared to be DOA.  The 1½" diameter knob on the top of the scope gives access to the oscillator, which can simply be lifted out.  Plugging it in and removing it a few times cleaned it's contacts and now it's working OK.  It again failed to start and cycling the oscillator up and down a couple of times fixed it.  Maybe it needs cleaning with a pencil eraser?

The original battery was the BA-1100/U 6135-00-926-0827 which is one of the long obsolete Mercury based batteries.  A prior owner has made a simple battery adapter by taking a four "AA" battery holder where all the cells are wired in series and attaching a metal plate to each end.  The "battery" goes into the scope Positive (+) end first.  The scope case is a negative ground.

The 4 AA battery holder has both the + and - terminals on the same end.  This adapter is made by placing a metal plate on the terminal end with the positive contact connected to the positive terminal and with epoxy or hot melt glue insulating the negative contact.  A diode is connected from the negative spring to the opposite end and goes through a small drilled hole to the negative metal plate that is glued to insulate it from the jumper eyelets on that end.  Single sided PCB material would be a good material to use for this.

The BA-1100 used 4 Mercury cells which when fresh put out 4 * 1.35 = 5.40 Volts.  When dead it was 5.0 volts.
If 4 AA rechargeable batteries were to be tried they would be about 1.4 V * 4 = 5.6 Volts fresh and 1.2 * 4 or 4.8 when dead.  So although they probably would work when fresh, the useful life would be short.
If 4 AA Alkaline cells are used the fresh voltage would be 4 * 1.52 or 6.08 which is a little too hot, that's why the diode is in the adapter to drop the fresh voltage down to about 5.6, very close to the Mercury battery.  The 5.0 volt dead voltage for the adapter occurs when the cell voltage is 1.4 so when the AA cells no longer work in this adapter they would still power a flashlight.

1100BA Battery Adapter

After working with the Battery Eliminator (see below) it's clear that 6.6 Volts DC is OK so the diode used in the above battery adapter is really not needed and not desired since it wasts energy.  The 1100BA product does not use a diode.


The brass disk contacts have polarity (+) and (-) stamped into them.  Also the label "TVS2 cap Positive" is on the Positive end.

Battery Eliminator

This is a battery eliminator that replaces the BA-1100/U Mercury battery that's long obsolete.  It's line powered from regular 115 VAC single phase power.

Power Converter for Night Vision Sights AN/PVS-2, AN/PVS-2A or AN/TVS-4 Input: 115 VAC single phase 60 Hz Output: 6.8 VDC	MS3110P-14-5-5P shown with pin A next to wide keyway at top. Letters go clockwise.	DC output is case threads and spring.

The A.C. cable will use a MS3116E-14-5S or MS3116F-14-5S or MS3116P-14-5S connector.  
The MS3116E-14-5S is the lowest cost and is available from William Perry Co.
Wiring is A.C. line to pins B and C.
Earth ground to pin E = threads on battery eliminator and connector shell.
Open circuit output about 6.6 Volts.
Although only three Night Vision Sights are listed on the batery eliminator it should work for anything that uses the BA-1100/U like the TVS-2B.
These are available from Mike Murphy on his NIGHT VISION, SURVEILLANCE   AND RELATED ITEMS web page.

TM-11-5855-203-10
Night Vision Sight, Individual Crew Served Weapon AN/PVS-2 (NSN 5855-00-087-2947), AN/PVS-2A (5855-00-179-3708) and AN/PVS-2B (5855-00-760-3869)

TM-11-5855-203-13 Organizational and DS Maintennance Manual, Night Vision Sight: Crew Served Weapons Models 9927 and 9927A, April 1967

TM-11-5855-203-23P Technical Manual Organizational and Direct Support Maintenance Repair Parts and Special Tools Lists (Including Depot Maintenance Repair Parts and Special Tools) for Night Vision Sight, Crew Served WeaponsAN/TVS-2 (NSN 5855-00-087-3144), AN/TVS-2A (NSN 5885-00-791-3358) and AN/TVS-2B (NSN 5855-00-484-8638),  November 1977 Change 1

TB 11-5800-212-24 Procedure for Determining Serviceability of Night Vision Sight Individual Served Weapon Sight, Crew Served Weapon AN/PVS-2 and AN/PVS-2A; Night Vision Sight, Crew Served Weapons AN/TVS-2B; Night Vision SIghts, Mimiaturized AN/PVS-3 and AN/PVS-3A; and Night Vision Sight, Tripod Mounted AN/TVS-4 and AN/TVS-4A.

TC 23-13 Crew-Served Weapon, Night Vision Sight, Jan 1967

See my Optics web page

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