Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login

Site Notices
Posted: 10/13/2016 5:56:49 PM EDT
Ok, here's the deal. I got a mum 14a housing and an Omni vii spec mx 11769 tube for my first nv build. The seller of the tube de soldered the manual gain control pigtail from the tube so it would fit in the housing. I assembled the unit today and powered it up to test. Looks great with day cap on, but image gets "snowy" with no day cap down in my crawl space. Haven't used it at night outside yet. I googled a bit and found that these tubes can potentially be damaged by powering them up with the pig tail removed. Do I just need to get a potentiometer or resistor soldered in to fix things or is it worse than that? Appreciate input from anybody that's got experience with an mx11769 tube in a housing that doesn't support manual gain. I realize the easy solution would be to just install a 10160 tube. Trying to make this current tube go, if possible. Thanks!
Link Posted: 10/13/2016 7:13:29 PM EDT
How does it look in your closed garage? More than enough light to replicate a full moon. Not enough to damage it. Mine sintilate like crazy in the closet
Link Posted: 10/13/2016 9:10:39 PM EDT
I have run into this before with a PVS7.

I *think* yours is running wide open gain. I *think* you may have to add a resistor.

For me, it looked like running water in mine. A teeny bit of IR illum made it happy.

Link Posted: 10/13/2016 9:16:48 PM EDT
Well I'm kind of scared to power the unit up until I can confirm that the absence of the pigtail (and associated electronics) won't harm the tube. This archived thread seems to be summarizing my exact situation.

https://www.ar15.com/archive/topic.html?b=6&f=18&t=440302
Link Posted: 10/13/2016 9:19:48 PM EDT
[Last Edit: 10/13/2016 9:59:40 PM EDT by marvthehamster]
The image was better with IR illum. It really got scintilicious with no IR in the dark of the crawl space. I too, think I need a resistor in there.

I see now that this issue has been tackled numerous times on this forum and others. Does anyone know who could solder the appropriate resistor across the pins for me so I can get this thing running?
Link Posted: 10/14/2016 5:36:52 AM EDT
Just as the thread explains (assuming without reading it, I'm sure you found out the right one), you need a resistor in place of the pigtail to set the gain to a proper level. It is not supposed to work without.
Link Posted: 10/14/2016 6:05:31 AM EDT
It's not a difficult job. I soldered a new pigtail on my unit with a $10 Weller soldering iron and a few minutes time, but it also wasn't my first time soldering. I can't recall what resistor value is recommended, but I'm pretty sure the info is floating around in the archives. Find a friend who's done electronic soldering before and they'll have no problems with it.

If you don't have any friends () or just want someone professional to do it, I'd talk to Ed at wilcoxeng-res.com. His website isn't much to look at, but he had my dog leg tail in stock and was responding to emails on the weekend.
Link Posted: 10/14/2016 10:17:23 AM EDT
Why someone would remove the pigtail on a milspec MX11769 is beyond me. Just get a proper housing ! That said it is not good to run it as is. You need to put a new pigtail on and put it back as it was or solder a resistor between the two contacts. I forgot the resistor value needed to use but have the information somewhere in my files. Maybe CJ7 knows it off hand. I will look for it. I would just solder a new pigtail on and get a proper housing.

Don't use the tube as it is now until it is sorted.
Link Posted: 10/14/2016 10:53:40 PM EDT
I agree that a 10160 tube would be preferable but the price was right on this one. I couldn't find a reasonably priced 10160 tube while shopping for this unit and the specs on this 11769 tube are pretty good (Omni vii).

So when the resistor is soldered in, does it sit down low enough to allow the light pipe and ocular lense to tighten properly? Seems like it might create an obstruction or clearance issues inside the housing. If it really is more trouble than it's worth, I'll trade the tube for a 10160 and be done with it.
Link Posted: 10/14/2016 11:05:44 PM EDT
[Last Edit: 10/14/2016 11:20:27 PM EDT by Dino1130]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By marvthehamster:
I agree that a 10160 tube would be preferable but the price was right on this one. I couldn't find a reasonably priced 10160 tube while shopping for this unit and the specs on this 11769 tube are pretty good (Omni vii).

So when the resistor is soldered in, does it sit down low enough to allow the light pipe and ocular lense to tighten properly? Seems like it might create an obstruction or clearance issues inside the housing. If it really is more trouble than it's worth, I'll trade the tube for a 10160 and be done with it.
View Quote


Trust me on this. Just call Ed and get a pigtail. Sell the tube and get a 10160. Hell, If the price is right I will buy it from you and fix it myself. Don't bastardize a MX-11769 tube. I know the resistor value but just can't say. Just not worth it. Sell the tube to someone who can appreciate it ! It is worth more then a 10160 tube so it is your gain !

ETA: Have a lot of 10160 tubes and can work a trade but in consideration of the work I need to do and the price of parts.
Link Posted: 10/18/2016 3:29:26 PM EDT
So I'm still on the fence about what I'm going to do with this thing. I have some calls/emails out to get pricing on converting the tube to 10160 (soldering in the resistor). I'm also open to selling or trading the tube for a 10160 but I'm leaning toward a conversion since I have this tube in hand and don't really want the hassle of coordinating another sale or trade right now.

Does anyone know a part number or manufacturer for the resistor that I would need? It appears that something in the neighborhood of 100k ohms is required? I looked at the diagrams in the pvs14 patent but I'm not good at reading circuit diagrams.
Link Posted: 10/18/2016 5:10:05 PM EDT
Astroscopes variable gain models used a 10-80k ohm pot.
A 62k ohm 1/8 watt resistor well works and fits. About 10 cents plus shipping.
Link Posted: 10/18/2016 7:15:41 PM EDT
[Last Edit: 10/18/2016 7:17:58 PM EDT by cj7hawk]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By falcom:
Astroscopes variable gain models used a 10-80k ohm pot.
A 62k ohm 1/8 watt resistor well works and fits. About 10 cents plus shipping.
View Quote

174K Ohms is the correct value. Within a few K-ohms is fine too.

Anything less will reduce your gain. Anything more may result in overdriving of the PSU, possibly resulting in unanticipated damage.

( note, if you want less snow, you will have to reduce the maximum gain. Smaller resistors will achieve this - eg, 160K, 150K or thereabouts. But the trade off is less gain. )

Regards
David
Link Posted: 10/18/2016 8:19:35 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By cj7hawk:

174K Ohms is the correct value. Within a few K-ohms is fine too.

Anything less will reduce your gain. Anything more may result in overdriving of the PSU, possibly resulting in unanticipated damage.


( note, if you want less snow, you will have to reduce the maximum gain. Smaller resistors will achieve this - eg, 160K, 150K or thereabouts. But the trade off is less gain. )


Regards
David

View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By cj7hawk:
Originally Posted By falcom:
Astroscopes variable gain models used a 10-80k ohm pot.
A 62k ohm 1/8 watt resistor well works and fits. About 10 cents plus shipping.

174K Ohms is the correct value. Within a few K-ohms is fine too.

Anything less will reduce your gain. Anything more may result in overdriving of the PSU, possibly resulting in unanticipated damage.


( note, if you want less snow, you will have to reduce the maximum gain. Smaller resistors will achieve this - eg, 160K, 150K or thereabouts. But the trade off is less gain. )


Regards
David


My PVS-14 measure between 30k and 128K full gain.
Best way is to try a potentiometer first and find what value suites you best then replace it with a resistor.
Link Posted: 10/18/2016 10:44:15 PM EDT
Super! Thanks for all the input.

Just so i have it correct....higher resistance equals more gain equals brighter image.....lower resistance equals less gain equals dimmer image? Or did i get that backwards?

Also, I'm finding resistors a plenty and have a guy that can handle the solder no problem...but what wattage should it be? Is that dependent on the resistance or is there a standard wattage that these things run on?
Link Posted: 10/19/2016 4:49:27 AM EDT
[Last Edit: 10/19/2016 5:32:34 AM EDT by murtis]
Yep, the higher the more gain, no resistor -> pretty high ohms -> too much gain. Wonder why it was designed like that, you'd think the PSU had an internal maximum.

Edit: btw, with MUM-14A do you mean the one on the left or right? If the rightmost, how much does it weigh, with or without tube or battery, I can add them back up if you have it disassembled.
Link Posted: 10/19/2016 9:10:52 AM EDT
[Last Edit: 10/19/2016 9:28:28 AM EDT by cj7hawk]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By falcom:

My PVS-14 measure between 30k and 128K full gain.
Best way is to try a potentiometer first and find what value suites you best then replace it with a resistor.
View Quote View All Quotes
View All Quotes
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By falcom:
Originally Posted By cj7hawk:
Originally Posted By falcom:
Astroscopes variable gain models used a 10-80k ohm pot.
A 62k ohm 1/8 watt resistor well works and fits. About 10 cents plus shipping.

174K Ohms is the correct value. Within a few K-ohms is fine too.

Anything less will reduce your gain. Anything more may result in overdriving of the PSU, possibly resulting in unanticipated damage.


( note, if you want less snow, you will have to reduce the maximum gain. Smaller resistors will achieve this - eg, 160K, 150K or thereabouts. But the trade off is less gain. )


Regards
David


My PVS-14 measure between 30k and 128K full gain.
Best way is to try a potentiometer first and find what value suites you best then replace it with a resistor.

"The fixed resistance value chosen in this embodiment is 174 kO, but it is understood that other values could be selected for other systems."

From the patent, which defines, exactly, where to set the maximum resistance ( max gain ) for the potentiometer - The mx11769 also uses this same exact figure.

and

"The maximum gain limit is set by connecting a resistor of a defined fixed value (preferably 174 kilo-ohms for example) between the pin 60, 70 pair and the pin 50, 80 pair, and then adjusting the potentiometer 160, to establish the desired maximum gain. The fixed resistance represents the maximum resistance of the external circuit in the night vision system, when the user's gain adjustment control is adjusted to maximum."

From the MX11769 patent.

Regards
David

ref: https://patentimages.storage.googleapis.com/pdfs/863538d6adf38386adde/US6288386.pdf
Ref2 - mx11769 - https://patentimages.storage.googleapis.com/pdfs/US6150650.pdf
Link Posted: 10/19/2016 9:14:13 AM EDT
I guess I hadn't forgotten everything my electrodynamics professor tried to teach me!

I have the mum 14a, which is the unit on the right. Weight is listed at 260 grams on the spec sheet, I think that is without a tube or battery installed. It is noticeably lighter than a pvs 14, which is the standard unit to compare against here in the states.

Anybody with info on wattage for the resistor?
Link Posted: 10/19/2016 9:30:58 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By marvthehamster:
I guess I hadn't forgotten everything my electrodynamics professor tried to teach me!

I have the mum 14a, which is the unit on the right. Weight is listed at 260 grams on the spec sheet, I think that is without a tube or battery installed. It is noticeably lighter than a pvs 14, which is the standard unit to compare against here in the states.

Anybody with info on wattage for the resistor?
View Quote

It's very low current - even if somehow the full 3v got dumped across it, it would be around 17 microamps, or around 50 microwatts. Any resistor that fits would be fine - :)

Regards
David
Link Posted: 10/19/2016 1:05:00 PM EDT
You guys rock. Thanks for the technical help. This forum certainly has its share of knowledgeable night vision guys. I know it's not the ideal setup, but at least the resistor can be removed and a pigtail reinstalled if I ever go to a pvs 14 or sell the tube. I think with the fixed gain it will suit my needs for the time being. I'm sure I'll learn a lot more as this project progresses. I'll try to post some images from the tube once I get her going so you can seee what I ended up with.
Link Posted: 10/19/2016 11:04:59 PM EDT
Yea, ok. After a bit of messing with these resistors and this process I think it's time to move on from this experiment. Dino was right, it's not worth the trouble (to me) to make a go of this tube in my MUM housing.

Who needs a blemed omni vii 11769 in exchange for a usable 10160?
Link Posted: 10/23/2016 9:45:26 PM EDT
Call me stubborn, but I'm back at this problem. I think a surface mount resistor would be the way to go if I solder one on. Does anyone know where I can find a 145k Ohm (ish) SMD resistor? These things seem to be sold mostly in bulk quantities but I don't have use for 5k resistors...
Link Posted: 10/23/2016 10:24:35 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By murtis:
Just as the thread explains (assuming without reading it, I'm sure you found out the right one), you need a resistor in place of the pigtail to set the gain to a proper level. It is not supposed to work without.
View Quote



This. Assuming it is an ITT tube, it needs a resistor.
Link Posted: 10/24/2016 4:44:44 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By marvthehamster:
Call me stubborn, but I'm back at this problem. I think a surface mount resistor would be the way to go if I solder one on. Does anyone know where I can find a 145k Ohm (ish) SMD resistor? These things seem to be sold mostly in bulk quantities but I don't have use for 5k resistors...
View Quote


Mouser and digikey are two websites I turn to when I need components.
Top Top