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Posted: 10/24/2013 10:32:05 PM EST
I have a set of ANVIS 9 goggles with MX1090C tubes that have just been serviced. They work great and have been awesome in the short time I've tried them. However I've noticed a couple quirks that I'm assuming is probably normal, but I couldn't really find any information on in my search.

The first thing I've noticed is occasionally when I flip on the NVGs, I'll see a wavy or squiggly thin black line when looking through them. They will disappear after maybe 15-20 seconds of being powered, but I'm just curious if this is normal. The strange thing is, if I look through the left tube alone, I will see the line, and if I then look at the right tube alone, I will still see the line in the same spot? I thought the tubes were independent of each other?

Also, I'm sure this next "quirk" has to do with the built in protection feature, but when I point the goggles at, for example, a fairly dimly lit light post (40w bulbs from approx. 100ft), the goggles will flicker on and off until I point them in another direction. I assumed the goggles would reduce power, but not flicker like that. Of course I have been trying to avoid any bright lights, but I wanted to find out what the threshold was.

I appreciate any insight as I learn how these goggles work.
Link Posted: 10/24/2013 10:52:48 PM EST
i use a similar setup but have not had those effects - could it be that when you flip them on there is a point of lite in front of you to streak both tubes , i have noticed that tubes are more sensitive to this streaking straight after switch-on . or if they have been on recently , have they been exposed to a lite just after switchoff as i have seen a sort of ghost image on mine when i turned them off and left them in a lit room for a few minits but it went away soon with use .
the only time i have seen the flicker is when the battery was down (on a monocular )
Link Posted: 10/25/2013 3:35:32 AM EST
[Last Edit: 10/25/2013 3:35:59 AM EST by Dino1130]
The first issue seems like phosphor persistence. It is normal and some tubes show this effect more than others. I have some that never do this and ones that look like a road map after a bout with some street lights. The second issue could just be the autogating feature. When you go from very dark to bright lights they dim quickly and it can look like a flicker. I don't think you have any issues here to be concerned of.
Link Posted: 10/25/2013 8:12:22 AM EST
Thanks for the replies guys. The first issue it could possibly be that I exposed it to some street lights that caused this, but it does seem to happen more often when I switch the NVGs on and off several times within a few minutes. They didn't have me too worried though since like I said they seem to disappear after a short while, but I wasn't sure if this was a sign of problems to come. But doesn't sound like it from your replies.

And as for the second issue, I think it could be a battery issue actually. I should probably try throwing in a fresh pair as I think they are getting weak But they would flicker on/off at about the pace of a turn signal when exposed to light that I otherwise thought the NVGs should be able to handle. Nothing like headlights from a car. How does the autogating feature typically work? When exposed to moderate light do they just dim the picture, and then when exposed to a harmful bright light turn off all together?
Link Posted: 10/25/2013 5:25:58 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Squawk1200:
How does the autogating feature typically work?
View Quote


Tubes have two circuits built into the power supply ABC and BSP.

ABC (auto-brilliance control) keeps the image the same brightness at moderate light settings. So at clear starlight illumination up to about 1/4 moon you have full gain, after that the ABC kicks in to keep the goggles from getting too bright. On an ITT MX-10160-C tube this will be about 4 to 4.2 foot-lamberts of output. On an L-3 tube this will be about 3.2 fL. This circuit works by lowering the voltage across the MCP.

BSP (bright source protection) protects the tube by regulating the voltage between the photocathode and MCP. If the current gets too high (bright light in the field of view) this circuit kicks in. On the older DC power supplies the power supply would regulate this by lowering the voltage. On Auto-gated power supplies this voltage is actually cycled on or off hundreds of times a second (about 1160 times/sec on ITT power supplies and 247 HZ for L-3 power supplies) When a bright source enters the FOV the power supply regulates the "duty cycle", i.e. the amount of time off vs on.

The chief advantage of auto-gating is that it keeps the voltage high. Keeping the voltage high keeps resolution high in high light environments.
Link Posted: 10/25/2013 7:54:06 PM EST
I haven't had any of those issues and I use I don't know how many different pairs of the anvis9 for work. Don't know if my company uses different tube setups but never had any of that happen.
Link Posted: 10/26/2013 11:18:09 PM EST
Well just to give an update, it seems replacing the batteries solved the flickering issue I was experiencing when exposed to a bright light source. I guess with the low batteries the autogating feature couldn't function properly?

Also, I finally pinpointed when I get those squiggly lines. It usually happens when I'm inside with not much ambient light (ie. really dark) and I point the goggles at say a LED on a stereo. I can basically paint a line with the LED onto the image tube, and then when I look at a brighter scene it'll stand out. Again, it'll slowly fade away in about 20-30 seconds. If the scene is already well lit with plenty of ambient light from the sky glow or street lights, then the tubes seem less susceptible to this "painting" effect. Anyhow, I still can't get over how amazing these things are. I'm always in disbelief when I flip the goggles up and realize just how dark it is. I keep thinking it can't be!
Link Posted: 10/27/2013 7:34:31 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Squawk1200:
Well just to give an update, it seems replacing the batteries solved the flickering issue I was experiencing when exposed to a bright light source. I guess with the low batteries the autogating feature couldn't function properly?
!
View Quote


Pretty much. The voltage on the circuit was to low to properly regulate, the flickering was the power supply hunting for the right duty cycle and probably cycling between gating and non-gating.
Link Posted: 10/27/2013 8:34:42 AM EST
[Last Edit: 10/27/2013 8:35:21 AM EST by TNVC]
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