Need help with power supply for old night vision scope... - Page 1
Forum section: electronics / repair

author: jntmjt1
author_rank: Newbie
timestamp: November 13, 2015, 03:36:48 am
content: I have an old (1970s era) Russian designed (Polish) military surplus night vision scope. It is not working, but I think it could be fixed with a little brain power.The entire setup consists of a power supply, the scope itself, and an infra-red light unit. The power supply is completely separate from the scope, and the scope has a mount for the IR light on top of it. The light & scope are connected to the power supply are connected by a long cable with three wires inside it. The intent is for the power supply to be worn on your belt, then the scope is less bulky to handle.The power supply contains a 6 volt, rechargeable, lead acid battery. There are three pins that provide power to the cable and ultimately to the scope. One pin is negative, one pin provides 6v (for the IR light) and one pin provides ~400v for the power to the scope.Well, my pin that should be supplying 400v is giving no power.I took the power supply apart and looked for anything obvious, but found nothing visually out of the ordinary. There are several (about 10) components (I'm no expert, so I'll just call them capacitors, resistors, etc) in the unit, so I suppose one of these components has gone bad.This leads me to a couple of questions. Is there a way to just rebuild the entire power supply with modern components so the bad pin will supply the required ~400 volts? Or... is there a way to possibly (with help from you guys) troubleshoot this thing down to the bad component that could be replaced or upgraded? I can provide pictures and take measurements with my meter, as required.Thank you!

author: helius
author_rank: Super Contributor
timestamp: November 13, 2015, 03:53:31 am
content: I think most of these used ferroresonant forward converters. You might find a schematic online or in an old patent that matches your unit.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 13, 2015, 06:23:11 am
content: Quote from: jntmjt1 on November 13, 2015, 03:36:48 amThis should be your absolute last option.Quote from: jntmjt1 on November 13, 2015, 03:36:48 amNow we're talkin'!Quote from: jntmjt1 on November 13, 2015, 03:36:48 amYes, yes, yes! As much information as you have about the scope the easier it will be for others to help. High res photos of the outside (one or two will do, just to get a feel of what you're working with) and plenty of shots of the inside ensuring that we can see everything that's going on.Let's see this bad boy

author: amyk
author_rank: Super Contributor
timestamp: November 13, 2015, 07:42:35 am
content: It's probably going to be something likea Royer oscillator, which is also the same basic circuit used in CCFL inverters.

author: jntmjt1
author_rank: Newbie
timestamp: November 13, 2015, 08:53:14 am
content: Quote from: tec5c on November 13, 2015, 06:23:11 amThis is great news! I hope we can get this thing going. It's the middle of the night, here. Tomorrow, I'll take some good photos of the inside of the power supply and put them up. In the meantime, I'll let you know that the system is a Polish NSP-2. A picture I pulled from google of the entire setup is below.Thank you.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 13, 2015, 09:06:40 am
content: How did you find out that one of the pins is meant to be 400v? Does it say this somewhere on/in the power supply?Edit: A quick google search led me to this blog:http://dragunov.org.uk/nsp2/Page_1x.htmlThere's a somewhat detailed teardown of the scope. It also mentions that the control module is potted with black silicon, which is never fun to work with.Edit again: Found this but I think it's probably too small to read, if you can even read Polish. However, it does seem like one of the pins does say x00, so presumably that's your 400v pin.Here's a shot of the control module...Is this what you had a look at already?

author: Jacek_Paw
author_rank: Contributor
timestamp: November 13, 2015, 10:19:57 am
content: Quote from: tec5c on November 13, 2015, 09:06:40 amHey, this is not i Polish but in Russian!Under this link you can see hand made schamtics of this power supply:http://obrazki.elektroda.pl/6396999500_1304709890.jpgI'm not sure if it is ok but maybe it will help you.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 13, 2015, 10:42:26 am
content: Quote from: Jacek_Paw on November 13, 2015, 10:19:57 amI didn't even see the title in big bold letters, wow.12 hours straight of study today (exams next week), I blame that.

author: jntmjt1
author_rank: Newbie
timestamp: November 13, 2015, 01:43:28 pm
content: Quote from: tec5c on November 13, 2015, 09:06:40 amOne of the connectors inside the unit is labeled "400v", plus another man who had trouble with his (on a firearms forum) told me in his troublshooting, he was getting voltage out of the pins. Going from memory, the thought one was 6v and one was 350v and the third was the negative. Which all seems to basically match up with my deduction of 400v. The guy from the other forum is away from home on business, but when he gets home, he plans to check that voltage for me. He got his working, but it was a dirty connector at the scope.The poster you have a picture of only shows the scope unit (with the scope control box, which is part of the scope unit). The unsecured end of the cable in the poster is what attaches to the power supply, which is not shown on the poster.The clear box you pictured is the "guts" from the scope control box on the side of the scope. Mine may be good, I can't get that far in my troubleshooting until I get the power supply providing the proper output. That is the box with tubes potted in black gunk.The power supply "guts" are not potted and should be somewhat easy to photograph and work with. I'll have photos up later today.Hopefully the drawings the Jacek_Paw posted will be of help. They look promising!Thanks you!

author: jntmjt1
author_rank: Newbie
timestamp: November 13, 2015, 04:34:48 pm
content: Quote from: tec5c on November 13, 2015, 06:23:11 amOkay... I spent a couple hours getting some really close-up and detailed pics of everything. There are about 50 pics. So, instead of posting them all here and blowing up the site, I made an album online.The link is here:http://s61.photobucket.com/user/jntmjt1/library/NSP2%20power%20supply%20internal%20componentsI had some trouble uploading the pics, so unfortunately a few of them are out of sequence. Also, if you view them in reverse order (page 3 first and page 1 last), it will probably make more sense to you. Each pic has text right on it explaining what I was trying to capture in the photo. So, hopefully you won't be too confused.The only thing that I POSSIBLY can comment on, from a visual inspection, is one component. It resembles a rheostat, so that's what I'm calling it. It has possibly a burnt or odd smell to it, and the wound conductor is a little darker in one portion than it is in the rest of the areas. I captured this in one of the photos, so you should see it.Please look through everything, and also look at the drawings that were supplied by the other forum member here, Jacek_Paw, and see if you can educate me on some things to check out.Thank you very much! I really appreciate your time. It would be so great if we can get this thing going.

author: Smith
author_rank: Frequent Contributor
timestamp: November 13, 2015, 04:54:29 pm
content: 1. Does it measure zero volts, or is there a voltage present?2. How many ohms do you measure between ground and the 400V pin?3. How many ohms does the cap marked 1968 measure?Building a separate 400V supply is not that hard, but it would be best (and cool) to repair the original one.

author: DmitryL
author_rank: Regular Contributor
timestamp: November 13, 2015, 05:05:38 pm
content: on image 12 there is a 1/2W red resistor (obviously). The clear tube thing with a lot of small disks inside is a HV diode, made of those diodes inside connected in series.img14: 0.5uF 400V, 5% paper capacitor, year 1954img18: a rheostaimg7: looks to me as a germanium pnp transistor P202

author: jntmjt1
author_rank: Newbie
timestamp: November 13, 2015, 07:21:17 pm
content: BIG UPDATE:After taking everything apart and getting the detailed photos, I put everything back together. Guess what. The power supply now appears to be working properly! There must have been a dirty connection or something that I inadvertently took care of while messing around with the thing.I have 6v at one of the pins and ~400V at another pin, which I can adjust that output with the rheostat. So, that is all very good news.Now for the VERY BAD NEWS... The scope still does not power up. The IR light is working (as it was all along... I can feel the heat coming from it). But, the scope is completely dead.I'll post some pictures of the scope control box, but digging into that may be a tough one. I'm still up for any help, though.Thank you.

author: helius
author_rank: Super Contributor
timestamp: November 13, 2015, 10:06:34 pm
content: The component in img38, Tungsram RB-3, looks much like a starter for a magnetic-ballast fluorescent lamp. But I cannot see any bimetal relay inside, just a filament. Is this intended to provide an increasing resistance ramp after the power is switched on, for soft-start or something?

author: tec5c
author_rank: Frequent Contributor
timestamp: November 13, 2015, 11:46:00 pm
content: Not sure of the technology back then but NV scopes/goggles of today will be damaged if they're turned on in too much light. As they're actually light intensifiers rather than "night vision".

author: jntmjt1
author_rank: Newbie
timestamp: November 14, 2015, 02:17:00 am
content: Quote from: tec5c on November 13, 2015, 11:46:00 pmThat is true, but this scope (as most of the older ones like this) has a protective lens cover with a pinhole aperture for use in the daytime.When I look through the scope, I just see total blackness... no green light of any sort.

author: moore
author_rank: Contributor
timestamp: December 06, 2015, 12:15:12 am
content: I don't know about this specific device, but in general these are very hard to fix beyond the circuits. The gold colored thing in the diagram above is the vacuum tube, and it has (1) a photocathode (2) a microchannel plate which is probably what the 400V is for and (3) a phosphor screen not much different than older TVs or oscilloscopes. If its lost vacuum then no dice. Theoretically you could make a small hole and connect a tube to a vacuum pump, but you have to make very deep vacuum to restore it. Likely it wouldn't work anyway, since moisture or oxygen exposure will damage the photocathode, and more slowly the microchannel plate.If all three components above work, and there is good vacuum, then if you put light in the front with the power applied, more light HAS to come out the back. It might be fuzzy if some of the optics are messed up, but there should be amplified light at least.