My image intensifier NV monocular is behaving strangely. - Page 1
Forum section: electronics / general

author: Ben321
author_rank: Frequent Contributor
timestamp: February 13, 2020, 03:05:34 am
content: I just received the FireField Spartan I ordered last week. I put in a CR123 battery and began testing it, but then it began to behave in a VERY weird way. When I pushed the power switch to turn it off, it didn't turn off. I could still see though it, and it still performed light amplification as if the switch was on. At first I thought the switch might have gotten stuck in the on position, but then I noticed the green power LED was off, indicating that power to the image intensifier tube should also be off. Again I thought maybe something was just broken, so I removed the battery, as the image intensifier can't run without the battery (no electronic device can run without a power source). And that's when something really strange happened. The image intensifier tube continued running. It continued amplifying light, just as if the battery was still inserted and the device turned on. The power indicator LED was off, and the IR illuminator couldn't be turned on, but the image intensifier tube remained running. Does the Spartan have some kind of backup battery or capacitor in it, that holds a charge long after the normal CR123 battery has been removed? Does the image intensifier tube itself hold some kind of charge that can last for minutes after the CR123 battery has been removed, and continue providing operational power for the tube? This is the first time I've ever used a night vision monocular, and I just want to make sure that it is behaving correctly, and isn't broken (and also isn't somehow haunted by a spirit, which uses its supernatural powers to provide electricity to the device even when the battery is removed). I don't usually believe in ghost hauntings, but what my scope is doing right now is VERY VERY STRANGE.

author: richnormand
author_rank: Unknown
timestamp: February 13, 2020, 03:32:05 am
content: I do not know what gen is your unit.My FIND-R-SCOPE IR to visible viewer does that. It has an IR sensitive coating at one end and a green phosphor at the other. It's like an imaging photomultiplier. In between, in the vacuum tube, there is an electron focussing electrode to accelerate and focus them and form the image on the green phosphor.Because it uses such a low current at a few kV the charge is held a long time by the overall capacitance of the unit. It has a push switch to energise it when the image gets dim (minimising battery usage). In strong light, the switch can be turned on continuously. I even have a slight burned spot looking at a laser reflection 10s of meters away in that mode from years ago.Test your unit and see how long it stays on in a very dim light situation vs a strong light situation, in the off position after energising it. You should see it decay rapidly in strong light due to increased current. If so, it looks to me as normal behaviour.Cheers.

author: Ben321
author_rank: Frequent Contributor
timestamp: February 13, 2020, 03:41:02 am
content: Quote from: richnormand on February 13, 2020, 03:32:05 amIt is a gen-1 unit. Gen-2 or better is too expensive for my budget.I was testing it with the pin-hole lenscap in place (which allows for testing at normal light levels), and the illumination of the scene was with my room's normal ceiling light turned on. I left it turned off and the battery removed for like a half hour, and FINALLY it seemed to have completely depleted its charge.

author: Fraser
author_rank: Super Contributor
timestamp: February 13, 2020, 12:28:12 pm
content: Ben321,As has been stated by Richnormand, this is normal behaviour of such a Gen 1 image intensifier tube.The tube does not normally need a continuous high voltage supply to operate. Many Gen 1 NV scopes have a momentary power button that is only pressed when the image starts to dim. It can be kept pressed of course to ensure the brightest possible image. The tube is very low leakage so once charged it will discharge at a rate dictated by the current flow caused by the scene striking its target. If the lens cap is kept on, the charged period can be quite long. This is why you have to be careful when using this Gen 1 technology. People sometimes charge the tube and remove the lens cap in a bright environment before the tube charge has dropped adequately. This is not healthy for the tube and should be avoided.To clearly illustrate the way the tube operates as a charge store, the Russians made piezo electric powered night vision scopes that utilise a piezo electric crystal that is squeezed by a lever mechanism. The high voltage produced by the crystal is applied across the Gen 1 image intensifier tube and it begins operating. When the image starts to dim a single press of the lever is all that is required to recharge to tube. The interval between charges can be quite long and the instructions explicitly state that thar the lever should not be ‘pumped’.As a rule, the brighter the observed scene, the shorter the period of operation before a recharge of the tube is needed to maintain the image brightness.Warning.... exposing a simple Gen1 image intensifier to a bright scene or a scene with a bright object, such as a halogen lamp in the FOV is potentially harmful to the tube and cause a burn that is permanent.Some users complain of black dots on the phosphor of Gen 1 NV scopes. They cam look like someone has sprinkled pepper over the phosphor ! Gen 1 tubes used in modern Russian jolt NV scopes can date back to The 1960’s ! Their were large stocks of these tubes stored in Russian warehouses from the Cold War era. They continue to be produced but Russian dealers advised me that quality can vary greatly. Gen 1 Tubes are tested and allowed a quality rating. The best have very few, if any, blemishes on the phosphor. The worst have a significant number of black dot blemishes all over the phosphor. These are manufacturing defects that are tolerated as the tubes sill function. It will come as no surprise that the better Gen 1 tubes are the most expensive and the worst tubes are the cheapest. Many budget consumer grade Gen 1 NV scopes either have tubes at the poorer end of the quality range fitted or operate on ‘pot luck’ where a range of qualities are used in production and some are better than others (the tubes are purchased in bulk as unsorted for quality).The better quality Gen 1 tubes with very few or no defects in the phosphor find their way into the more expensive civilian NV scopes and come with a guarantee of phosphor quality.I have many Russian NV scopes and saw many identical units rebranded by Western resellers. The NV100 by Moonlight is a classic example. It used ‘bottom of barrel’ poor quality Gen1 tubes and I could buy one for $30 in Moscow Circa 1996. In the UK the same unit was selling as the NV100 for £149 ! Another Russian model that looked very Russian in design (utility rather than pretty) was the Cyclops 1. It was another budget NV scopes that I could buy in 1996 for $30? It was pot luck whether you got a reasonable quality tube so we were allowed to test them at the market and select one we likedThere were better quality NV scopes that contained higher quality (lowers phosphor defect) Gen 1 tubes. An example was the White Night that cost me $100 in 1996. It was well built with a solid metal body and the image quality was excellent on all the units I tested at the Moscow market. The sellers recommended this model for serious Gen 1 night vision work as the the manufacturer selected and used only good quality tubes for them. One of my best Gen 1 NV scopes is nothing pretty but has superb performance for Gen 1 and a large IR illumination that has a ‘zoom’ feature. The unit looks very utilitarian..... almost militaryand operates on a Lithium 2CR5 battery which was very uncommon in NV scopes of the time I was in Moscow. It was made in Belarus by a scientific instrument manufacturer and uses the very best quality Gen 1 tube that was available to them. The tube is a lot bigger than those used in common consumer units like the NV100 and Cyclops 1. The powerful IR illumination has an adjustable range control for best illumination of a target at varying distances. The phosphor of the high gain tube is free from blemishes and the produced image in the eyepiece is large compared to other NV scopes. I bought a lot of NV kit from the seller and he got to know what I liked so he bought in the Belarus unit for me. It was around $120 but was worth every penny. He also offered me a Gen 2 military NV sight that was clearly ‘liberated’ from a military platform ! He was asking $1000 in 1996 which was a lot of money back then. I passed on that offer as I did not fancy carrying stolen Russian military Gen2 NV technology through Airport Security. I could have ended up in very hot water. I could have ended up as a guest at the well known Government Hotel Lubyanka !https://en.m.wikipedia.org/wiki/Lubyanka_BuildingAs a side note..... I also worked in Kyiv, Ukraine and was offered various NV equipment in the markets. By then I had plenty so was less interested in buying more. A Western chap that I met in a bar offered me Gen2 military NV equipment ! It had been stripped off of Russian Tanks that were being transported through Ukraine on slow moving trains ! Needless to say I did not buy any and made my excuses before putting plenty of distance between myself and this entrepreneurial Western Black marketeer !Ahhh those were the days, I miss them !Fraser

author: Fraser
author_rank: Super Contributor
timestamp: February 13, 2020, 01:19:36 pm
content: Ben321,I just took a look at the NV scope you have purchased. It is made by one of the well known Russian or Chinese manufacturers of NV kit for the consumer market. It is actually a pretty standard Gen 1 NV scopes dressed up in pretty clothes. It is one of the ‘pot luck’ brands so some of these scopes will be better than others from the same production batch !Some dealers do sort through the units and select only the better quality examples for sale to the West. As already stated, the quality of the tube in your unit will be clearly visible by the quality of the phosphor and number of black dot defects. Distribution of such defects is also a factor in the quality determination process. I hope you got a good unitFraser

author: Ben321
author_rank: Frequent Contributor
timestamp: February 14, 2020, 06:16:10 am
content: Quote from: Fraser on February 13, 2020, 01:19:36 pmWhen you say that Firefield is one of those "pot-luck" companies, do you mean they don't actually manufactures their own complete NV scopes? They just take the image intensifier tube out of an already-existing scope (probably an old used one from the cold-war era), and put it in a new body (which they do manufacture, and looks nicer than the body they got the tube out of)? Or do you mean they do manufacture their own complete scopes (including the image intensifier tube), but their manufacturing process is poor, so some tubes are better than others by random chance?

author: Fraser
author_rank: Super Contributor
timestamp: February 14, 2020, 11:14:29 am
content: Ben321,The tube that is inside your Firefield will be a low cost type that is unlikely to have been tested and selected for performance. Hence my term ‘pot luck’. It will work fine but may have more or less black dots on the phosphor depending upon luck rather than testing. Really bad tubes are likely filtered out so you are unlikely to get a very poor tube in a Firefield product. The instructions likely mention defects in the phosphor as a normal production characteristic and not a fault in terms of warranty. If I had a bad one, I would demand an exchange though !I believe your Firefield scope is also sold under the “Yukon” brand. There is a lot of rebranding of these products. A generic product is manufactured and resellers have their brand applied to the outer casing. The main sources of these budget tube based NV scopes are Russia and China.It is fair to say that you get what you pay for with Gen1 night vision scopes. In any range of NV scopes, the lower cost units will likely have more phosphor defects present as there is less quality control during production and fewer checks on the final product. That keeps costs down. In many cases the customer is the Quality Control inspector ! Cheaper tubes may also have less gain but the simple Gen1 tubes are pretty low gain anyway so this is less of an issue in the real World. The range of gain specified for a cheap tube may be quite wide, whereas a better quality controlled tube may specify not only higher maximum gain, but a smaller range of gain in the specification.It is fair to say that the Russian units were/are of reasonable quality if you do not buy the ‘bottom of the barrel’ cheapest units. The Chinese made units were very variable on the quality front but have been improving thanks to Western resellers demanding better quality control (to avoid customer complaints). It is possible that Chinese made NV scopes are using Russian made Gen1 tubes as Russia was a major producer of such tubes. The Chinese may also be making their own now that the vast warehouse stocks in Russia have been depleted.As to the tube in your night vision scope, it will be new and not recovered from another NV Scope. Tube recovery would make little financial sense when new ones are so cheap. The tube will be either Russian or a Chinese copy of the simple Russian design that has been around since the 1960’s, if not earlier. It is fragile so it is best to not drop your NV scope as it can misalign the phosphor screen inside the tube. I have worked on a few victims of dropping and the tube can also crack due to the impact.There is a thread detailing what resides inside the Zenit NV100 Russian NV scope. It was sold in the UK under the name Moonlight NV100 and it represents the “bottom of the barrel” in terms of quality and performance. It is made in Russia and contains a relatively poor quality Russian Gen1 tube.https://www.eevblog.com/forum/repair/ussr-transistor-identification/I attach some pictures of the Gen1 tube design commonly found in Russian and Chinese Night Vision equipment.I have repaired a fair few of the Russian and Chinese NV scopes over the years. They all seem to have weaknesses in the HV inverter and these tend to fail rather than the tube, even if it is a tube from the 1960’s ! Repair depended upon whether the switching transistor or inverter transformer had failed. The transistor is an easy repair whereas transformer failure basically renders the unit a parts donor.Fraser