Hi there,

since AR15 seems the most active forum about night vision related stuff, here are a few pictures and probably repair attempt of a defective Fujinon PS-910 MNVD. Unfortunately it does not power up. More about the symptoms below the teardown.

Teardown

This is the device without the battery cover (2x AA batteries). The front lens was already missing when I got it.


Ocular side.


Input side.


To remove the ocular unscrew the bezel, underneath there are three screws connecting with an aluminum ring which is clamping down the outer plastic ring in between.


Loosen the locking screw and unscrew an aluminum ring which is holding the handstrap.


To remove the front cover there is a small setscrew beneath the S/N sticker. It seems like a previous attempt for repair was made and the setscrew was not loosened....


Front cover removed, exposing the image intensifier.


Unsolder the wires on the PCB and get the IIT out.

Image intensifier
Now for the Image intensifier tube. With the fiber optic input I suspect it's a Gen. 1+ tube?
Some ads from the 90's claim the PS-910 has a "hybrid image intensifier" and "brightness equivalent to second generation intensifiers".
Is it possible to tell Gen. 1+ and Gen. 2 apart when looking at the unpowered tube?


Photocathode


Phosphor screen

Image intensifier dimensions: 52 mm diameter , 50 mm height. Photocathode diameter 18 mm. Phosphor screen diameter 10 mm, without fiber optic.



Any clues what kind of tube I have here?
The outer case looks like some I have seen from DEP, in the inside there could be a XX1201 IIT. Of course this is just a guess.

The symptoms
When powering up, the input current is 127 mA @ 3V and a whining sound can be heard. The Tube does not light up.
The input current seems way to high, I expected 30-50 mA. It seems like the oscillator is working and I hope the tube is still alive but there is an insulation breakdown or a failure in the voltage multiplier.
Any information about possible failure modes of IITs?

For further tests I propably need to "depotting" the IIT. Any information how this could be done without harming the tube or powersupply?
if everything fails I might need to get a X-ray image of the intensifier to locate how to disassemble it.


Best regards,
Fleisch

before you take the tube apart it might be worth getting it dry as you can - just in case any dampness has got inside the power supply and is causing the problems

There is a member here that repots tubes all the time @DTS-blackout. If he doesn't chime in soon PM him. As for the tube, "hybrid" was a term that was used with Gen2+1 type tubes back in the day like the MX9964 and a few others. 127ma Does seem high in terms of current, but not crazy high. IIT's can fail for alot of reasons, going to air (loosing vacuum) is one main cause. Is the PC actually the color it looks to be in the photos or does it look weird due to the camera, usually the fiber optic inputs look blueish/greenish/reddish not black/white like yours appear.

good mx9916's


and I can't find  a good pic of dead 9916 for comparison, but the PC looks grey/browinsh typically.

I suspect your tube is gen I, a common "trick" to increase output brightness on single tube inverting gen 1 systems is to have the photocathode of a larger diameter than the output screen. I've seen this on Russian devices and Oldelft's single stage systems. I've never seen it on a gen II tube due to the mechanics of the MCP, but it could be a possibility. I have also seen that photocathode color in an American and Delft gen 1 triple stage tubes that were still functional (perhaps a sign the tube is going bad, or the color of the S20 photocathode vs. the S25 typically used on gen II systems?).

If you rule out the housing, the HV power supply on the tube, or the tube itself may have kicked.