Reverse Engineering a U.S. Navy Vacuum Tube Thing

In this episode, we take a look at a U.S. Navy vacuum tube… thing! A member of my Discord server sent this cool little piece to me and after pouring over for it a couple of days straight, I still have no clue what it does, but we have a pretty good idea of how it does it!
Here’s a high resolution picture of the schematic: i.postimg.cc/HLjVCnTf/Navy-Sc...
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Intro Music adapted from:
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Title: The Shinra Shuffle
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Thanks for watching!
Chapters
0:00 Intro
2:00 First look
6:20 The schematic
13:24 Powering it up
17:08 Outro
18:18 Bunny!

[@uniservo]

That is a piece of sonar gear. The idea was that you would mount this thing to the edge of a Bearing Deviation Indicator to give you a more known precise bearing. While the BDI could give you a good indication to plus/minus five or ten degrees, this gizmo would allow for a much better visual indication of just a couple of degrees by pulling signals off the BDI. When you were pointing at a target, the eye would be fully activated, and any amount that you were off would be deactivated. Sort of a late war add-on to the system.

[@TheEmbeddedHobbyist]

I was going to say navy radar, so Sonar fits as well. Navy as its painted grey, army would be green, all aircraft equipment in the copit has been blue and in avionics bay black. They are the colours im used to working on in the UK.

[@UsagiElectric]

I think you absolutely nailed it! That makes a lot more sense and fits perfectly with what we're seeing, thank you so much!

[@kennye6088]

What sonar are you talking about. I worked nearly every sonar system there were, from the British 1938 ASDIC to the US 1992 upgraded MK 26 sonar system. And none of them had an eye indicator. Radios yes, Fire Control yes, Loran yes, DF systems yes. The first Sonars all used the 4" CRT tubes.Followed by the 6" and then 8 and 10" CRTs. By 1952 the US move into the MK6, and for longer time the Mk7 with a 12" yellow CRT. The US kept Mk 7's up to 1964.The electronics remained the same, but the transducers all were improved producing different Marks. The sonar plates were improved too, for better 360 deg search. Then we went hybrid and then digital by 1979. I even installed PUFFs on submarines.

[@uniservo]

These was used with some of the early world war 2 sets like QCP, QCU, etc. sets that were NOT given an CRT. These were used with the CQA-55098 or CBM-55105 Bearing Deviation Units. I have one of these little units at home - maybe I can find it.

[@byterock]

@@uniservo CQA-55098 that was a a rather larger wall unit. Could be a later version 50s I know they evolved to have plugins. Will have to check later catalogs. Maybe it is 1950s not 40s. One of the chaps at the radio club suggested it was a post war build form the stitch and fuse arrangement.

[@piscesmikey]

My dad was an EE and I grew up around a bunch of VT technology that was sitting around, along with his huge suitcase of replacement tubes. It all kind of seemed out dated, out of fashion, and archaic coming up.. but now it evokes strong memories of listening to him talk about how components worked, cathodes, anodes, and etc. Although I did not pursue an electronics career I did gain a fair bit of knowledge about how it all works that has greatly benefited me in life. I started with a Timex Sinclair 1000 back in the 80's and learned programming, and machine code at a fairly young age. Now, this is all extremely fascinating to me, and I've got to say, it's great seeing people like you still working with, designing, and using this technology. Wish I had of spent a little more time learning on it....

[@UsagiElectric]

Thank you so much! My father was an EE as well, and he tried to teach me some stuff growing up, but I was young and dumb and didn't listen. Now though, we often work and figure stuff out together and it's a huge amount of fun!

[@augustinchenault9981]

The conformal coating is called MFP, moisture and fungus proofing. It was used in electronic equipment in the 40s and 50s that was intended for active field service. The two diodes in the last amplifier stage are for detecting the signal on a carrier wave going through the signal path (radio purpose).

[@UsagiElectric]

Oh very interesting, I didn't know the official name for the conformal coating, but that makes a ton of sense given the damp and salty environments that Navy gear was destined to be used in!

[@your_utube]

Mr Carlson's Lab is the channel where this thing will be deciphered for sure.

[@m.m.radiochannel1969]

Send a request to Mr. Carlson lab....

[@UsagiElectric]

If Mr. Carlson shows an interest I'll be happy to send it along to him! Though, I have to say I think the mystery has mostly been solved by the amazing commenters in here! I went back and double checked the Magic Eye connection and I totally missed an important connection to B-. Here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png Also, another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a perfect application for it!

[@paulstamp1208]

Curious Matc is also excellent

[@KeritechElectronics]

Magic eye tubes need negative DC input voltages (with respect to the cathode) hence the rectifier that shunts the positive halves, leaving out the negative ones. And since 12SQ7 is a triode and two diodes sharing the same cathode, the manufacturer connected both diode plates together and used the diodes as signal rectifier. The device is basically an AC level indicator. It's indeed beautifully built and sturdy as hell. Something that can inspire amp builders, and what most modern electronic equipment lacks.

[@UsagiElectric]

That makes total sense! I also missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png It really is immaculately well built and an inspiration for how things definitely should be built!

[@ArveAsheim]

What happens is that when the voltage is positive, the 2n condenser is charged and then when the voltage goes down, the diodes have no resistance and the grid goes negative. So it is basically for a DC shift.

[@mikegLXIVMM]

I like the way military equipment was made, especially old tube equipment. 1st class quality, built to last.

[@UsagiElectric]

It really is built extremely well! I wish modern stuff was built as solidly as this thing!

[@simonzinc-trumpetharris852]

I used to build gear like this. Very high standards.

[@soniclab-cnc]

I had a similar unit from an old ww2 military radio setup. I believe the magic eye was for measuring signal width or something to that effect. It was also beautifully built and over engineered.

[@BogTheWombat]

As a thought - is it for some form of tuned system - such as a resonant power supply or an antenna network to give an indication that it is falling out of tune or that the alignment of two moveable elements has shifted (hence the instruction about being trained)

[@UsagiElectric]

It certainly could be used for that! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems the most likely. Although, it's entirely possible that this one unit was used for multiple purposes given that it's designed in a pretty generic way!

[@beakytwitch7905]

I could use it with a signal generator for lining up the IF stages in a superhet radio. You basically inject a circa 450 kHz signal amplitude modulated at say 400 Hz and tune the IF slug for maximum response. This device amplifies the signal coming out of the filter, then detects it and displays the audio frequency amplitude on the magic eye. With a superhet radio, the receiver's own circuitry does this amplifying and detecting and the audio amplifier and loudspeaker is used to tune for max amplitude. If you are testing or trimming an IF transformer on its own, then this device supplies the necessaries to detect the response.

[@UsagiElectric]

I'm not going to lie, most of that went way over my head! I'm a total newbie when it comes to radio stuff (being deaf in one ear makes audio projects... difficult), but I'm certainly fascinated by the near black magic level skills required to do it properly!

[@woodyTM]

Hmm, I figured it would need 400hz because not only was it potentially used in a nautical setting, but it's also military spec. The wiring being 'over built' made me also believe that. Absolute treat and an amazing video!

[@UsagiElectric]

Thank you! You know, I totally didn't think about that, but you're absolutely right! Most Navy gear is expecting 400Hz AC power, so I was probably feeding it with quite a bit less frequency than it was expecting.

[@marklatimer7333]

Well Done Usagi, you seem to have started arguments between several ex-military guys all of whom must be in their late 70s to mid 80s, I sincerely hope I still have that much spunk left when I get to their ages, which unfortunately aint that far away.

[@UsagiElectric]

Haha, I'm surprised how many people found interest in this little device! The feedback has been absolutely amazing (if not a little bluntly delivered)!

[@videolabguy]

The rectifier diodes are wired as a classic voltage doubler. The rectified voltages are centered around the ground on the junction of the two filter caps. The magic eye tube is essentially an inertia-less galvanometer for measuring very fast voltage change. Some sort of carrier signal, possibly modulated, is coming in, being amplified by the 12J5 triode, and the triode section of the 12SQ7 and then rectified to a DC level by the two plates coupled to the 12SQ7's cathode. The 1629 is just being an eye tube. There are many variants. They are extremely simple. This entire device is an over glorified, yet highly sensitive, vacuum tube volt meter. Either a tuning indicator or a display for an RF or sonar proximity detector. Submarine or ship anti collision device if I had to guess. FYI: The magic eye tube was invented by Allen B. Du Mont of oscilloscope fame. Before that tube, he was famous for inventing the "long life" cathode ray tube. Prior to Du Mont, CRTs were of the Braun tube variety (pronounced "brown", not "brawn"). The Braun tube used an unheated tungsten spike for a cathode, required up to 100,000 volts to work and had a notoriously short life span. A few hours at best. X-rays were discovered in Braun tubes very early on. But, that is another story. Du Mont produced CRTs with indirectly heated cathodes and solved the problem of short life and lethal operating voltages... when he was 18! Prior to that, he won a competition at age 16, sponsored by the Dairy Association to find a replacement for heavy glass milk bottles. Du Mont invented the waxed paper milk carton, which is still in use today (juice boxes) and won the competition, all before 1920! He won $10,000! Back then!

[@UsagiElectric]

Thank you so much for the excellent reply! As for the 12H6, I don't think it's a voltage doubler. I checked the voltages in the circuit, and it's only showing rectified DC at about 135V. It's a bit lower than I was expecting, but I suppose with the voltage drop across the diode and the potential mismatch of capacitor values for a 400Hz supply versus the 60Hz I was feeding it, it does make some sense. Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment. Also, on the topic of Braun tubes, in Japanese, CRTs are still called "ブラウン管" (Braun tube), which is ironically where I learned the proper pronunciation of "Braun"!

[@krzysztofwaleska]

@@UsagiElectric 12H6 has max plate voltage 150V. 120V AC * 1,41 = 170V DC. So one diode is not enough. Additionally pair of diodes when in series have doubled internal resistance. It allows using bigger capacitor for better filtration. Additionally filtration is better due to higher internal resistance of rectifier. I would strongly suggest of using some kind of AC power supply with current limit. If not, then old-style incadescent light bulb in series with tested device can save device. Then something goes wrong, light bulb shines, nothing more happens. When all is ok - light bulb flashes at power-on, then glows very weakly. It's good to have few bulbs with different wattage, ex. 15W, 50W, 100W and perhaps 300W.

[@annaplojharova1400]

It is not doubler, it is really a halfwave rectifier. The configuration is such in order to accept power from 2 phases of 400Hz 3-phase onboard power, arranged as 3x85V in Y with (weakly) grounded center and allows the negative power side to be AC grounded.

[@jlawrence71]

@videolabguy - Thanks for the mention of Allen B. Du Mont. I was not aware of this guy and really enjoyed reading up on him and his contributions to our craft. Super Interesting !!!

[@rolandlastname5532]

This is to detect variations of the amplitude of an AC signal. It is to be hooked up to some sensor, who knows, perhaps sonar as others suggested. The knob is to adjust for the 'normal' level so that an abnormal level is easy to notice on the magic eye.

[@UsagiElectric]

Thanks for the insight! It's a surprisingly simple circuit inside, and it may have actually been designed to be used in multiple different setups, kind of like a universal detector.

[@MikeFreda]

Cool video. I like how this was laid out. It inspired me to do something similar for a shop stereo system.

[@UsagiElectric]

Thank you! And anyone reading this comment should definitely check out Mike's build, it came out looking stunning!

[@TheDiveO]

The input rectifier diodes are actually in series (as per your schematics), so this doesn't look like redundancy. Maybe its rather for halfing the reverse voltage across each diode?

[@UsagiElectric]

Oooh, that's a good idea too! I didn't think about it from a standpoint of reverse voltage. Although, with vacuum tube diodes, the reverse current has to be absolutely massive for their to be any current through the vacuum (like enough to arc inside the tube). So it may be more about moving enough forward current per plate instead?

[@TheDiveO]

@@UsagiElectric I'm no tube expert, but you have rather small distances between anode and cathode, also not sure how much (space) charge is there still around. Doesn't the data sheet give this information? Of course, the max allowed reverse voltage might be more than 2x peak-to-peek voltage but this can be checked.

[@UsagiElectric]

@@TheDiveO True, it is quite a small distance. In the datasheet it lists peak inverse voltage as 465V, which is quite a bit more than I think will be applied here. The 12H6 can only supply about 40mA per plate max, so it could very well be for both increased reverse voltage protection as well as current.

[@jamesharrison7469]

2 things, 1. The 12H6 is likely connected as a voltage doubler one plate and the other cathode tied together. This would give about 200-250 Volts from the 115 input, lots of voltage drop. 2. The cathode of the magic eye is connected to the negative bus. the 2 diodes in the 12SK7 are used to rectify the output from the plate of the tube and give a negative signal for the magic eye.

[@UsagiElectric]

You're absolutely right about the magic eye, I went back and double checked it and I missed the connection from the cathode to B-. Here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png However, I don't believe the 12H6 is connected as a voltage doubler. I checked the voltages with it powered up and coming out of the 12H6 it's sitting at just 135V. That's actually a little lower than I was expecting, but accounting for voltage drop across the diode and the mismatch of capacitor values for 60Hz as opposed to the 400Hz of shipboard supplies, it makes sense.

[@billharris6886]

Interesting unit, obviously some type of tuning indicator, World War 2 era. The R/C coupling signal into V1, acts as a high-pass filter, rejecting frequencies below 8 kHz. That 12H6 is a detector diode made for a receiver, when used as a rectifier, it has a maximum AC input of 150 VAC so, the diodes in series help to derate the 12H6. The curious part is the series filament resistor; why is it in a fuse holder. Makes me wonder if this unit is made to operate on more than one line voltage, with the resistor value changed out accordingly. The diodes in V2 are used to clamp the AC signal, pushing the whole waveform negative, so the positive peak (assuming the signal is a sinewave) is referenced to 0 volts. That was a good idea to redraw the circuit to make it easier to understand the signal flow. The abnormally low value of plate resistor used with V1 and V2 is used to extend the high frequency response of these stages, to roughly a top end of 1 MHz, at the expense of stage voltage gain, which is likely 3 to 10. The 0.5 uF cap across the grid and cathode of the magic eye tube is used to filter out any AC component, so the eye indication will be stable.

[@UsagiElectric]

Oooh, that's a brilliant idea about the series filament resistor being interchangeable! I bet that the system was designed to be used for multiple applications on different ships, and in WWII the shipboard supplies may have varied quite a bit from ship to ship. I actually did make a mistake on the circuit regarding the Magic Eye tube. I went back and double checked and I missed the connection from the cathode to B-. Here's hte updated schematics, which make way more sense: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png Thank you so much for all the excellent insight!

[@zick1955]

It's most likely calibration tool for some sort of equipment, all that circuitry does is provide adjustable signal amplification level and provide power to the eye tube.

[@UsagiElectric]

It very much so could be! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application as well, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@zick1955]

@@UsagiElectric Comment by "uniservo" right, yeah that's what most likely it is, plus it kind of weirdly fits "calibration tool" description... Also multi use is also possible since it can be easily used as amplitude indicator for calibrating something.

[@danbrit9848]

I love the vacuum tube it uses as a Graff ...I buy them every time I see a listing online lol I find tubes with visual components are mezmerizing

[@aaronbrandenburg2441]

Just don't use a red clean tube as an indicator LOL

[@aaronbrandenburg2441]

Also I've heard about tubes that were essentially a self into getting a shift register component that were used in some old scrolling message displays in large format! But there were actually metal to Sophia quartz window I believe it was forwards to be determined if it was red plating! There was some pretty cool indicator tubes back in the day and even touch display tubes but it would require a hundred KZbin videos or more to even scratch the surface in my opinion

[@UsagiElectric]

I totally agree, visual vacuum tubes are gorgeous! Nixie tubes, Neons, Magic Eyes, small CRTs, even VFDs, they all just look absolutely amazing!

[@danbrit9848]

@@UsagiElectric I was trying to make a magic eye vu meter but I can't get the sensitivity right it even will Graff the noise in it's ac input lol...but threw my fiddling I sum how ended up with a magic eye heart beat censor lol by just holding a wire in my fingers

[@adrianrevill7686]

The rectifier means it can accept supplies that are centre-tapped or with one side grounded.

[@johngalt7382]

It's a meter that can be set to indicate a desired level. With several stages of voltage gain. It should be extremely sensitive (edit) AC signals only.

[@UsagiElectric]

It's so simple yet super cool, which I think is why I drawn to the mystery of its use! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@TheBananaPlug]

For the magic eye tube to work properly the beam control grid electrode needs to see a negative voltage, the diodes effect this operation. This is a normal setup.

[@UsagiElectric]

You're absolutely right! Though, I missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png With the schematic laid out like that, it makes a lot more sense now!

[@AlejandroLopez-qd3xm]

I wouldn't be suprised if it is meant to be fed from a 400hz source, rather than the 60 hz from the utility. Because of the relatively smal filter caps. You can do some math to find the frequency range of the signal expected based on the coupling caps. Probably IF

[@kennye6088]

400hz, was considered special freq. It came about in the mid 1950's with the arrival of the Mark-14 and Mark 19 gyro compass. Giving the US Navy its roll and pitch outputs. During the time of early missile development. It allowed the transformers and the synchro units to be made smaller. But prior to 1949, all voltage sources were 24v DC or 110 -440 volts AC. The Navy used the ARMA Mark 7 mechanical gyro compass or the Sperry Mark 10 or Mark 12 mechanical gyro compass. They were big, and had a room all to themselves.

[@UsagiElectric]

You may be right on that one! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment. Unfortunately, without knowing someone who is intimately familiar with these (which is getting more and more difficult given the time frame), it may be tough to lock down exactly what it was used on.

[@simonkormendy849]

My guess is that it is part of an antenna tuning system, it monitors the output of an RF amplifier that has a tuned parallel LC circuit, so the idea is to tune the LC circuit for maximum power output, my theory anyway.

[@UsagiElectric]

It very much so could be! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application as well, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@TeslaTales59]

Always excellent up close photography. Great content always. I think it's a VU meter. Send pics up to Canada to Mr. Carlson. He would enjoy this creature!

[@UsagiElectric]

Thank you so much! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment. If Mr. Carlson expresses some interest in it, I'll be happy to send it his way!

[@johnbartlet6669]

Are you familiar with Paul Carlson at Mr. Carlson's Lab channel? You should have a look at his variac/isolation transformer/current limiter setup. It's pretty slick and not difficult to build.

[@UsagiElectric]

I am indeed familiar with Mr. Carlson's Lab! The majority of stuff I do is pretty low voltage DC stuff, so I hadn't ever really needed a variac or isolation transformer. But, given how much fun this was to play around with, I may start working on more old stuff like this, in which I'll definitely need to get my hands on one!

[@RWBHere]

It's a simple signal level indicator. They were used domestically for tuning TV receivers and radios. The military would likely use them for sonar, as someone else said, or radio signal tuning.

[@dalemettee1147]

Just remember, when building a piece of equipment for the government, sturdiness and dependability were the primary goal. Most components inside were the highest quality. An example is diodes were rated as Jan (joint army/navy) TX (bench tested and 'burned in').

[@UsagiElectric]

Oh yeah, absolutely! In particular, Navy usage environments were often damp and filled with salty air, so everything had to be doubly resilient. I just love seeing equipment over-engineered like this!

[@OldBaldGeek]

I can smell that wonderful military conformal coating aroma from here...

[@annaplojharova1400]

I think the magic eye cathode is connected to the negative common. That way one of the 1Meg resistors becomes a detector bleeder leak load, the other is the filter (with the capacitor)...

[@franklinwerren7684]

I built a Heathkit audio tracer with a magic eye tube and it did the exact same thing… after 55 years it still work even though it is a little beat up!!!!

[@odindimartino597]

The magic eye's cathode go to the negative side. I think you should verify the resistances in the magic eye circuit.

[@UsagiElectric]

You're absolutely right! I missed an important connection form the cathode to B-. Here's the updated schematics! i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png

[@byterock]

Well I had a look though some 1950s a JAN and AN catalogs and could not find your device. Going to get an Old Cro friend of mine to have a look at the video he might be able to identify it. From the plate that is on it and the fact it has no JAN or AN it on it I am leaning to something that was never accepted as standard issue. By the way the metal tube are glass on the inside. The metal case was just a way of cutting down on hum and other interference same as a tube shield you see on the first stages of an old AA5.

[@UsagiElectric]

Thanks for getting your friend to take a look at it! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which makes a bit of sense given that it's designed to give a more precise indication of incoming frequency. But, I think it was originally designed in such a way that it could have had multiple uses on several different types of equipment. Really, anything that needed a precise frequency indicator! Also, excellent catch on the metal tubes! Interestingly the 12SQ7 is a glass tube with a metal enclosure, but the 12H6 is a full metal tube. So, this piece has the whole gamut of tube variations, haha.

[@christiantreldal1585]

It's an external vu meter. Connect it to a audio output, and you will have a visual, quiet and sensitive indication of activity.

[@vasilis23456]

The original discord green circle indicator

[@UsagiElectric]

That makes the most sense! I was mostly curious what application it would have been used in originally, but a few other commenters have placed it as a sonar device, which is awesome!

[@railgap]

a U.S. Navy VU meter, that's some real solid reasoning right there.

[@SoundOfYourDestiny]

@@railgap Huh, I guess you weren't aware that USA's WW II submarines had on-board discos to keep morale up.

[@richardhaas39]

@@railgap I was in the Navy. Our VU meters were made b General Mills, the same company that makes Cheerios.

[@Peter_S_]

Every 1629 schematic I've seen has the cathode grounded or very very close to ground so I suspect a little more tracing is in order. The 1M inline with the cathode looks out of place. Army tube systems I've worked on at least all come with technical manuals which describe every last aspect of operation so while you'll find ingenious thinking here and there, it all seems to add up quickly and it's generally very conservatively designed. I can't speak for Navy tech. I have two potential use guesses.... #1 is as an antenna tuning indicator, and #2 is this might be an auxiliary level display for a radio direction finder to be placed near the helmsman. It's not part of any fire control (weapons) system I'm familiar with.

[@UsagiElectric]

You're absolutely right about the magic eye! I went back and double checked it and I missed the connection from the cathode to B-. Here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@kennye6088]

It is a 5" 38 rangefinder alignment unit for fire control MK-1a or b. It was located in the gun turret as you align the rangefinder the eye tube closes as you turn the range knob on the fire control analog computer. It was used for firing the weapon at night. Because the visual rangefinder was of little use on moonless night or very low light, and your spotter could not see where the round fell.. And those in the turret needed to know that the weapon was on point. It gave the "gun captain/turret captain a visual indication of weapon's range setting by the computer. The gun captain would look at the gun's range/elevation mechanical markings on the gun, he would get a report from fire control that their computer showed the set range, and the eye would be fully closed. Performing a three point check. A 5" 38 had a range of 18,000 yards approx. 9 miles.

[@uniservo]

Close, but it is for sonar. 5 inch guns already had visual feedback this late in the war, better than this little box.

[@byterock]

Hmm doubtful, do you have an JAN or AN number for it.

[@ianmathews]

Civilian here, Looking at KZbin on the MK-1 computer, likely this is not the case, however after 30 minutes of a MK-1a rabbit hole on KZbin, I thank you for sharing such a cool piece of engineering history.

[@UsagiElectric]

Somehow I missed this comment! That's an interesting suggestion that it might be for a rangefinder. The MK-1 fire control computer is a fascinating piece, and being an electromechanical analog computer (a really advanced pinball machine, hehe), I imagine it had all sorts of displays for relaying information to the user.

[@davidduma7615]

Going back to the engraved instructions..."when equipment is trained" certainly sounds like artillery. Do you "train" anything else? Of course, all I know about the Navy comes from KZbin... Drach and Battleship New Jersey.

[@adamquantrill]

It might be measuring AC but the envelope is smoothed to 0.3Hz by the 1M and 500nF (or possibly 0.15Hz). This seems like a deliberate part of the design, to remove noise, modulations, or flutter from the detected signal.

[@adamquantrill]

Just seen the updated schematic, yes 0.3Hz.

[@UsagiElectric]

Thank you for the insight! That makes sense, the designers probably wanted the magic eye to be nice and smooth.

[@Pulverrostmannen]

The diodes on the magic eye tube is to charge negative voltage on the grid, the more negative the grid gets the more the eye close, you can see the diodes as a type of charge pump on which the positive voltage pass trough the diodes and negative voltage stays. the tube is cathode biased and the diodes let the positive voltage pass to the ground and charges up the negative voltage on the grid so that the eye can close. the stronger signal the more negative will this voltage become. this device is basically a two stage amplifier driving the indicator tube. It can be used to monitor AC voltages or voltage impulses. it might have been used to calibrate signal receivers or monitor alternator voltages or other cool stuff, or simply as a VU meter. it could be used for many things back in the days

[@UsagiElectric]

You're absolutely right about the Magic Eye diodes! Although, I also missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png Also, another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but you're right in that it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@Pulverrostmannen]

@@UsagiElectric yes and the updated schematic is absolutely looking as it is accurate now. I am almost tempted to build that sometime and test what it can do. Great work Usagi!

[@Mooff2]

It would help if you would tune the input signal amplitude and frequency around to see what happens. I think I’ve seen a device like that used to aid in tuning in teletype signals on a short wave radio.

[@Pootycat8359]

It acts as some sort of AC voltmeter. The input cap & 10K pot have an RC constant of 20uS, which corresponds to a -3dB frequency of 50KHz for a H.P. filter, so it's for RF use, probably LW or MW. The 12H6 diodes are simply a shunt rectifier, and the two resistors & cap are to smooth the pulsating DC. That configuration is commonly used for RF probes. So, that's what it is. Exactly what it's used for, I don't know.

[@user-yn6zw8tl3g]

こんにちは！日本人です！ いつも見て楽しませてもらってます！ マジックアイ美しいですね〜！

[@UsagiElectric]

こんにちは！ いつも見てくれてありがとございます！ 私もそう思います、マジックアイ綺麗な色ですよね！

[@byterock]

Old Cro friend of mine did not know what it was sorry. The best he could come up with as a tuning matcher. In the days before counters you would set the frequency on set X with it then use it to see how far off set 'Y' was with it.

[@SeanBZA]

Would say the magic eye is operating correctly, with the diodes pumping charge into the grid capacitor on negative pulses, and then on the positive pulses the cathode is being clamped, slowly draining away the charge while still operating the tube. Likely was used to set some sort of system, probably onboard ship intercom, with various channels having preset levels to set the dial, then adjust till the indicator closes on tone being put in. 2n coupling capacitors about right for audio. Using the 2 diodes likely because the designers had a stock of tubes around, so used the dual diode ones, as they knew they would be available as spares, and common, so no special parts to add to inventory by the manufacturer. Remember the manufacturer had to supply the spares as well, as part of the contract, so really was incentivised to reduce the number of different parts used, as they likely had to supply x number in total for the ship install, so having a common part meant no extra paperwork to enter it, no certification, and no need to put more money into the spares box.

[@UsagiElectric]

You're absolutely right! Though, I missed an important connection from the cathode of the 1629 to B-. Here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png This actually confirms your thinking even more! The diodes are pumping negative charge and the grid capacitor holds that charge during positive pulses. Also, that's excellent insight about the manufacturer having to supply the spares, I totally didn't think of that. It would definitely make sense to use tubes or parts that were used in other systems built by the manufacturer to cut down on the variety of spares that had to be used. Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which makes a bit of sense given that it's designed to give a more precise indication of incoming frequency. But, I think it was originally designed in such a way that it could have had multiple uses on several different types of equipment. Really, anything that needed a precise frequency indicator!

[@nigel-matthews]

That’s definitely a CRM 114 Discriminator

[@brandoncochrone5582]

Ha Stanley kubrick reference 👌

[@nigel-matthews]

@@brandoncochrone5582 I see you’re a man of culture!

[@UsagiElectric]

Major Kong riding the nuke down like a bucking bronco is one of the all time greatest scenes in movie history!

[@TheBigChill1]

Is an RF Modulation detector level indicator for Radio Operations... Those "magic eye" tubes were a feature of many quality radio receivers in the 1940's

[@UsagiElectric]

That's a good guess! I'm not sure if it's related to radio operations or not, but it was probably designed in such a way that it could be used with multiple difference machines.

[@byterock]

Ok I think we at the club have narrowed it down a little. Most likely a stand along part of a Frequency Meter. Much like the AN/URM-79 (this is an airforce item) but rather than a CRO it uses the magic eye. The CRO on the 79 was a simple XY and the 'Lissajous' pattern would be used to dial things in or out as the case may be. Still looking for an exact match ;)

[@UsagiElectric]

Oooh, the AN/URM-79 is a cool piece and I think you're getting close! Thank you so much for all the effort you're putting into figuring it out!

[@RA-Arg]

I love 6e5 (or 6e5 type) !!!!!!!!! man how many memories of my time as radio ham!

[@UsagiElectric]

Magic Eyes are really just beautiful pieces aren't they!

[@kennixox262]

This type of military electronics of this era was beautifully engineered and as you say, over engineered to work in harsh conditions.

[@jonka1]

The power input looks like a voltage doubler. Check the HT it's likely 240v. Also the matal box caps are likely leaky and need to be replaced, at the very least you should check them at HT voltage for DC leakage.

[@UsagiElectric]

I don't believe the 12H6 is connected as a voltage doubler. I checked the voltages with it powered up and coming out of the 12H6 it's sitting at just 135V. That's actually a little lower than I was expecting, but I think that's due to voltage drop across the diode and I think the capacitor values are intended for 400Hz shipboard supplies as opposed to the 60Hz I was feeding it. As for the capacitors, I don't really want to replace any components inside so it can keep it's original construction. At this point, it is primarily a display piece that will spend 99% of its time unpowered, so I'm not too worried about any components not working at full capacity in there.

[@byterock]

Ok showed a picture of it at our club meeting tonight and no luck with a positive ID but the general though is a prototype of some form as it does not have an ID plate. There is most likely space for it on the front where the 4 screws are. As well can you check to see if only one or the fuses are wired up. That would be a spare. The fuse means it was not designed for aircraft. They also had a look at the schematic it might be a compression amplifier for RF.

[@UsagiElectric]

Thanks for showing it at the club meeting! A shame that we didn't get a positive ID though. I'm still thinking the Bearing Deviation Indicator is the most likely guess!

[@byterock]

@@UsagiElectric Well we are still working on it. So far is looks like compression amp or a level converter for demodulating radio teletype signals.

[@sagnhill]

I wonder if you could make 1/4 inch phono inputs and outputs into it and use it as a distortion box for a guitar amp. ;)

[@senolcavusogullari]

Looks like Morse code visual indicator for noisy environment in order to help decoding visually , can be used in aircraft in very noisy situations or in submarine when complete silence is required.

[@bronka42]

nice VUmeter!! (turboencabulator aligment tool?) built like a battleship... a heavy one... "no clue what it does, but we have a pretty good idea of how it does it!" jaja! make my day

[@UsagiElectric]

Thank you! I love the way this thing is overbuilt! The comments are full of excellent suggestions to its use though. I think the most likely is that a commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems. But, I think it was originally designed in such a way that it could have had multiple uses on several different types of equipment. Really, anything that needed a precise frequency indicator! Either way, I'm stoked that it works so well and looks as cool as it does!

[@paul.alarner6410]

its simple,its a double ended rectum paralyser,used a lot in most navys lol

[@UsagiElectric]

I feel like there should be a warning to not Google that, haha.

[@MandrakeFernflower]

Vacuum tube driven colonoscope?!??

[@_f355]

if I think of it as a black box with a signal input and an eye tube output, it is clear that the device is a calibrated display of some sort, i.e. you're supposed to calibrate it by adjusting the gain under controlled conditions and then do the "real job", whatever that might be, watching the eye tube and keeping it at the same level by doing whatever you're supposed to do with the "real job" equipment. I can't think of any other application.

[@UsagiElectric]

You're definitely on the right path! I think another commenter figured it out as a Bearing Deviation Indicator for sonar systems, which fits right in line with your black box logic!

[@dalemettee1147]

The company that I worked for at the time dealt with DOD contracts, so everything was top quality, or supposed to be. So, I was used to seeing all the components were good.

[@UsagiElectric]

It depends on the equipment, but some military stuff is really excellent quality stuff! (Some can be pretty shoddy though, haha)

[@Strike_Raid]

Wow, using a 6H6 as a power rectifier; I bet that has never been done before. I imagine the two of them in series are simply to handle the load. The diodes in a 12SQ7 are demodulators (normally), they sure don't flow much current.

[@UsagiElectric]

You know, now that you mention it, the 6H6 is certainly not the best rectifier tube on the market, haha. I think you're totally on point that the two are in series just to provide enough current for everything else!

[@alejandrogamero4764]

I think that cheking a frecuency sweept input on J2 would tell us more about what was it designed for.

[@UsagiElectric]

That's a good idea! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@tedrobinson372]

The tube types are pronounced twelve J five, twelve SQ seven and twelve H six. The number preceding the first letter is the filament voltage.

[@UsagiElectric]

I'm surprised so many people were upset by the way I pronounced the tube numbers. I'm well aware that the first number is representative of the tube voltage, and when talking to someone in person, I do say "twelve." The reason I said the numbers individually here though is due to my personal background in aviation. You always say numbers individually when talking over the radio to avoid confusion. A tail number of N2059E is pronounced "November two zero five niner echo." You most definitely do not say "twenty fifty nine" or any other variation. To me, talking on camera is similar to talking over the radio, and when saying things like part numbers or model numbers, I try to make an effort to say each number individually, just as you would in aviation.

[@tedrobinson372]

@@UsagiElectric I supposed the pronunciation of the tube types has been standard since the format was introduced by the RETMA in 1933. Sounds odd pronouncing the filament voltage as individual digits after nearly 90 years.

[@richardhole8429]

You are forgiven. You do such good investigation we all want you to talk like an old time pro. None of us old timers would ever say one two for the filament voltage and think "rookie" of the one who doesn't know the lingo. I bet you know the difference between filament and heater. Tubes with separate cathode are heated with a heater. Tubes where the cathode is the heater are called filaments but note that by the 50s most tube circuit were separate cathode and heater-filament were informally confused.

[@bradstearns5384]

If you run the speaker output from an amplifier into it you might have yourself a nice vu meter. More eye candy beside your stereo.

[@Pootycat8359]

Here's a guess. Longwave was commonly used for Naval communication & navigation. This could be for peaking the output of a LW transmitter, or for signal strength in a receiver.

[@dadandkids5028]

Used for setting RTTY (radio teletype) signal levels.

[@UsagiElectric]

Oooh, that's an interesting idea! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@marka1986]

If eye tubes weren't so rare it would be cool to include that in your audio setup.

[@UsagiElectric]

I'm not going to lie, a little part of me thought about salvaging the magic eye out of it, but it's just so cool and still works so well that I just can't bring myself to taking anything of the unit. Fortunately, I got my hands on some 6FG6/EM84 tuning indicators recently that I think will make excellent VU meters for future audio applications!

[@frankowalker4662]

Looking at all the domino caps, I'd say it was for tuned radio something or other. (?) It's a nice looking whatever-it-is, in nice condition. :)

[@UsagiElectric]

Thank you! And it really is in excellent condition, I just love the over-engineering that went into it! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@frankowalker4662]

@@UsagiElectric I wonder if you could interface it to your valve computer ? LOL (Just Joking)

[@FirstLast-vr7es]

Possibly some sort of buffer that makes sure an input signal of some kind is at the correct level for a subsequent piece of equipment in a stack. I love the way it's built. Not terribly surprised that it still works.

[@RA-Arg]

The way it is built is fenomenal, army equipments are the best!

[@UsagiElectric]

Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment. It's build quality and design is top notch though, I just love the over-engineering of it!

[@aldoali6173]

interesting gizmo, lovely bunny, good video

[@UsagiElectric]

Thank you! The bunny is just the best, even if she does make a mess on the occasion :)

[@lucasfeth2624]

i don´t know for what is really used, but i am sure that this fing can calibrate a Fi from any type of radio. Its basicaly an "audio voltmeter"

[@UsagiElectric]

Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which makes a bit of sense given that it's designed to give a more precise indication of incoming frequency. But, I think it was originally designed in such a way that it could have had multiple uses on several different types of equipment. Really, anything that needed a precise frequency indicator!

[@electronicarchaeology]

Maybe because it's from the US Navy, my thought is it could have been connected to a magnetometer for mine sweeping during the war, but the list of uses for a vintage magic eye VU meter is endless though.

[@UsagiElectric]

You're absolutely right that a Magic Eye indicator could be used for hundreds of different things! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@weekendwarriorweldingdiypr4604]

Looks like it is for tuning something. It reminds me of aligning a radio, with the eye tube to be used to show when a section has been peaked. Maybe a military radio alignment tool?

[@UsagiElectric]

That's a definite possibility! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems the most likely. Although, it's entirely possible that this one unit was used for multiple purposes given that it's designed in a pretty generic way!

[@AdamosDad]

It's been 55 years, but I think it's a piece of LORAN or TACAN, I was an ETN2 so this was a little out of my wheel house but I think I remember seeing it in one of those spaces while hanging out with friends.

[@matthiasseidel6084]

Could one of the 1meg resistors be connected to ground instead? That would make sense to me as that would represent a common mode rc low pass filter removing interference above some khz.

[@randygraff2825]

I'm curious if you were two adjust the frequency of your 2 V signal. If that would affect the eye opening or closing which I've imagined it would.

[@UsagiElectric]

I actually did give this a try and it totally does! The higher the input frequency, the sooner the eye closes, which makes sense given that these are often used as frequency indicators or the like.

[@duality4y]

these kind of magic eyes always make me think of my grandfather he was a radio amateur

[@UsagiElectric]

These magic eye tubes were often used as tuning indicators on old radios. My grandfather bought a Magnavox Concert Grand radio new in 1962 and it has a beautiful little magic eye right on the front too!

[@derlowe4590]

What a beauty!

[@UsagiElectric]

I just love the aesthetic of it!

[@akkudakkupl]

That is a rail splitted supply, you have +80 and -80 referenced to ground. No idea why, but probably it was done for safety? If one of those diodes dies you would still have the other rail. Looks like a circuit that detects if a signal is a 50/50 square (or maybe doesn't have DC offset if it is a sine)? I might be mistaken though, just going by feel here ;-) Probably Mr Carlson would be able to tell.

[@UsagiElectric]

That's an interesting idea! As far as the circuit is concerned, 0V to +160V is the same as -80V to + 80V, so it really depends on what the ship was supplying and how the supply interacted with the "Earth" of the ship. Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@lansdragon2542]

Какая невероятная техника, очень похоже что наши инженеры учились местами у вас. Сильно похоже на то что делалось до 70х годов у нас. Не зря мои знания пригодились. Я понимал что это какой то усилитель и индикатор сигналов. Но вот для чего.. хз.. в теории это применимо для целого спектра радио оборудования. Скорее всего у нас такое встречалось но в весьма специфичной технике. При ссср в 60х годах мы в этом явно не уступали! Гарантирую. Сейчас увы.. мы проиграли эту битву. У нас не осталось тех людей которые могут в иновационные технологии. Протите. Мне жаль что нашей стране так не повезло..

[@mixmashandtinker3266]

Don’t be sad. You guys constructed some fine stuff too. You won 1:st object orbiting the earth and first man in space.. So you aren’t all that bad.

[@UsagiElectric]

Thank you for the excellent comment! And sure, America was pretty quick with innovation from the 40s to 60s, but there is something special about the overengineering and work done by Soviet engineers. One of my favorite phrases is "Limitation breeds innovation," and Soviet engineers had a ton of limitations from parts availability to budgets. As a result, they often came up with really innovative ideas for solving problems!

[@georgegonzalez2476]

Looks like a sonar peak indicator. If you adjust it as written, then any signal increase causes the two illuminated sectors to overlap and make a brighter region. Sonar because the coupling capacitors are too small for audio. The circuitry is a bit odd as the input low side goes to a cathode at minus 150 volts plus ripple. So it must be a transformer secondary driving the inputs, otherwise the ripple would get amplified too. Weird. Also as others have noted the eye tube cathode needs a different path to b-. Take some care as the brown varnish is a toxic mercury fungus-proofing compound. Don’t eat or inhale it.

[@georgegonzalez2476]

And oh, might those 22K resistors actually be 220K? Fungus proofing can make yellow look like orange.

[@UsagiElectric]

I think you're totally on point with it being a sonar device! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application. Also, you're absolutely about the magic eye! I double checked the wiring and missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png The 22k resistors are indeed 22k. They actually measure out at 22.1k on my DMM, which is insane given they're carbon composition resistors, and those like to drift a lot.

[@georgegonzalez2476]

@@UsagiElectric Well I'll be dipped! I used two cans of "brake cleaner" to mostly remove the MFP from an old SX-28 radio. Many of those were sent to the hot and humid South Pacific so they really needed that poisonous brew slathered on everything. The service manual says to use Carbon tetrachloride, a liver cancer causer, to wash off the mfp off any terminals before unsoldering. Then afterwards the manual says to reapply the MFP. Musta been strong fungi if it attacked soldered joints! I can't imagine fixing one of these radios in the South Pacific. Deep dark compartments, mostly brownish resistors, and 90% humidity and temperature. We have it easy by comparison.

[@RA-Arg]

In the back is this antenna connection??, maybe is something related to RF (xmitters) just to calibrate signals

[@UsagiElectric]

I think that's just a standard connection terminal used for the system it was meant for. Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@lwilton]

I have to say that you pronunciation of the tube numbers kept rubbing the hair on the back of my neck backwards. The pronunciation would be "twelve J 5" and "sixteen twenty nine". The thing is Navy equipment, from the grey panel color. The conformal coating is a varnish that is designed to resist fungus. The Army and Navy quickly discovered in early WW II that tropical areas resulted in fungus spores in the air that loved to eat the insulation off of insulated wires and produce effluvia that corroded everything else in the equipment, destroying it in a matter of hours to days. The varnish prevented that. The wire lacing was Mil standard, and was useful for keeping things from flapping around when the equipment was moved or jarred, as one could expect in combat conditions. The thing is obviously a signal strength indicator, and from the legend on the front it is a tuning or training indicator used with some sort of directional radio equipment. From the use of "trained", it is most likely a radar unit or gun director unit. I'm really surprised by the lack of a part number on this unit. EVERYTHING in the WW II military had part numbers on them! If we had that it would be trivial to see what equipment it came from. Since it is a signal indicator on a trainable device, it would probably have been used to make sure that you kept the aim on target, as the eye would open when the signal strength dropped off. Standard WW II paper caps were made in ratings of 200V, 400V, 600V, and higher. Given the operating voltage, the obvious choices are 400V or 600V. If that really is single rectification coming in, 400V would be sufficient. But that looks like a voltage doubler circuit to me, developing half wave rectified voltages across C5 and C7 in opposite polarities, giving about 330V across C6. You could try measuring that. With that, 400V becomes marginal from a lifespan point of view, so the conservative choice was 600V filter caps. Note that line is balanced coming into the unit. Navy ship electrics didn't have a 'hot and neutral" as we are used to. The whole power system was floating with respect to the ship, and if anything needed to be tied to the ship's frame, it was a center-tap point, only giving 60V from ground to either rail. The first stage is a self-biased triode AC amplifier. The second stage is a grid leak biased triode AC amplifier. These two will get a low-level AC voltage (probably in the few hundred millivolt range) up to the 5-8V levels needed by the grid on the magic eye tube to achieve full cutoff. The magic eye tube needs a slowly varying negative DC voltage to produce a useful indication. The cap on the plate of the 12SQ7, in conjunction with the paralleled detector diodes in the 12SQ7, are a negative voltage source, rectifying the plate signal to a negative DC level. The cap between the grid and cathode of the 1629 is a filter to make the signal level change slowly. Detector diodes were designed to rectify low-level signals to produce a DC voltage level, not DC power. These diodes have a very low current rating, around 100ua each. When using them for uses like this it was standard practice to parallel them for reliability and current handling capacity, and to average the offset voltage that a thermionic diode generates. I'm pretty sure there is an error on your schematic on the magic eye tube. There is almost certainly a missing or incorrect connection to the cathode, which most likely should be returning to the ground reference used by the other tube's cathodes. The target current for the 1629 is going to be around 3-4ma, and you aren't going to be pulling that thru a 1M resistor to a pair of detector diode plates (rated for 100ua each) to ground. I would more believe that the detector diodes go thru a 1M to pin 5, and the thing you have labeled 1M on pin 8 is either a lower-value resistor to the negative bus, or just not there at all and there is a wire to the negative bus.

[@byterock]

Nah not use on a targeting system. Radar targeting systems of the the day used PPI and the data from them with their optical sights where fed into predictors that trained the guns.As well this is a stand-alone device as far as I can tell and not part of a larger system

[@lwilton]

@@byterock Someone in another comment said that this was an add-on to a sonar sub-finder system that gave a more accurate bearing deviation than the regular indicator used on the unit. I'm not much familiar with WW II sonar gear, but the clips I've seen of operators using the stuff makes it look primitive compared to WW II radar units with either PPI or the previous more primitive timeline-amplitude display, so I can believe that it was an add-on for a sonar rig.

[@UsagiElectric]

Thank you so much for the massively in-depth reply. Unfortunately, I somehow missed this comment a few weeks ago, sorry! Firstly, sorry about the way I pronounced the tube numbers. The number of people that got extremely angry at me for that is mind boggling. I address this a bit more in an upcoming video, but the specific reason why I pronounced the numbers individually is because I have a background in aviation. When speaking over the radio, we would pronounce the numbers individually to ensure no confusion. If I'm landing on runway 19, I say "one nine" not "nineteen." It just so happens that speaking to a camera, particularly when you can't see my face, triggers the same muscle memory, and I was pronouncing them individually and not even noticing it. Thanks for the insight on the conformal coating, that makes perfect sense! That also explains why everything inside is still in beautiful shape. The lack of part number is what really makes this one a difficult nut to crack. I'm thinking that perhaps this was a unit that was used for sales, or training or something, which would explain why there weren't any stamping on it. Also, it's quite likely it's just a small part of a much larger system that has a part number that encompasses this piece. You're definitely right that there's an error on the magic eye tube schematic. I missed the connection form the cathode, and going back and double checking it, it seems super obvious now! Here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png This makes a lot more sense now!

[@Kanthon]

I’ve seen those magic eye things on capacitor leakage testers.

[@UsagiElectric]

They have a ton of great uses! But mostly, they just look awesome!

[@lelandclayton5462]

That could go to anything from radio to some sort of sensor.

[@UsagiElectric]

Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but you're absolutely right that it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@gibsondrummer]

What would you do with it now ? Could it be re-purposed into a musical instrument tuning thingy?

[@UsagiElectric]

It's mostly just a display piece now. But, it totally could be repurposed into an audio VU meter, and with the gain control, it could easily be tuned to display using the full range!

[@byterock]

Well had a little more time for research. Lets go with what we know of the device. 1) it is not a sub-assembly or sub chassis (front panel has silkscreen, no set pins, knobs flush with plate, etc) 2) It has no JAN/FN or AN markings. 3) It is built to Mil-spec standards, 4) Plate it does have is blank, 5) could not be found in period catalogs. 6) could be a plugin to larger system. So what is it? Well one guess is a manufacturing test piece. During the war many companies where drafted to produce electronics, this could be a test run though a production line of a simple product to check for quality. IE to 'Boston Toaster Company' if you want to make radios for us take this schematic, and create it if it passes you get to build radios for us.

[@dadw7og116]

I like the sonar suggestion. I was thinking it was maybe a tuning indicator for an AM transmitter. The magic eye was used for a lot of things. One advantage was it's high input impedance. But, since you have input amplifiers, that does not appear to be the reason here. The other reason was its fast response time. It could even be used to indicate at RF frequencies. (The input circuit looks like it can go above audio frequencies. Have you tested its frequency roll-off?) You're only hint so far is the front panel instruction: "set gain to close indicator shadow to a fine line with equipment trained and tuned for maximum". One of the things these were used for in the days of AM was to indicate full modulation of transmitters. If the input signal was proportional to RF output, then you would tune your transmitter un-modulated (carrier only) and then set the gain on the magic eye so that it just touched. Then when you speak (modulate), set your microphone gain so that peaks cause the magic eye to touch. Anything over that would over-modulate your transmitter and cause splatter/harmonics. Anything less would reduce the power of your spoken voice. However, this does not explain the "equipment trained" phrase. Since there is no equipment number or manufacturer, it may have been a prototype or maybe something that plugged into another piece of equipment. You may want to try to trace the equipment source back through the person that you received it from...

[@UsagiElectric]

Thanks for the ideas! The tuning for maximum voice without causing clipping is a really smart idea for Magic Eye tuners. Though, I do think the sonar bearing deviation indicator is the most likely. Unfortunately, the person I got it from tried to figure out more about it before sending it to me, and the military surplus store he got it from didn't know anything about its origins or even who they got it from. Our best bet is finding someone who remembers using this in situ, but that's getting harder and harder as the years roll on.

[@johng.1703]

to me it looks like radar range finding equipment for target resolution. or some sort of tuning.

[@blitzroehre1807]

There is something wrong with the magic eye circuit the way you drew it. It cannot light up with the 1 meg resistor between cathode and ground. The cathode of the 1629 should be connected directly to ground. The module appears to be an add-on for sonar equipment to accurately determine strength of the received ping, hence the vernier on the gain knob.

[@UsagiElectric]

You're absolutely right! I went back and double checked the wiring and I missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png And I think you're spot on with the sonar equipment idea!

[@autobotjazz1972]

it this unit was designed and built for navy use the over building would be understandable as reliability would highly important, The coating on the wires would likely to be protect them from potential corrosion by the salty air at sea.

[@MostlyPennyCat]

I wonder if stuff like the 600V Caps are so it can survive the EM spike from a nuke inducing huge spikes in the supply.

[@futurepig]

I think you got a piece of the USS Eldridge there.

[@doogie812]

If it is not for looking at sonar pings it is a $5000.00 toilet seat. When I first saw it i was thinking some sort of wheatstone bridge but you shot that down instantly.

[@UsagiElectric]

I think another commenter nailed it, they suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application!

[@danbrit9848]

If you are in ca I'd have a thing made by the military but as a prototype it has a joystick made from an 8 ball of all things ..it has no tubes in it but from those years and has it's cercectry diagram hand drawn on papers inside it...I'd love to know what it was for or did and I know it would make a cool vid...but I don't trust shipping it and it's heavy also my most prized thing lol

[@UsagiElectric]

I'm a long ways from CA unfortunately! But, if you don't mind, hop on over to the Discord server and post up some pictures of the unit and hand drawn schematic, we'd love to check it out!

[@stphinkle]

I wonder if they are using the dual diodes as a voltage doubler circuit.

[@UsagiElectric]

A few other commenters actually had the same though, but I don't think the 12H6 is setup that way. I double checked the wiring and the schematic in that part is correct (I did miss a connection from the magic eye to ground though). I also checked the rectified DC voltage and it's sitting right at 135V, which is actually a bit lower than I was expecting. But, I believe this was intended for a 400Hz shipboard AC supply source, which would mean that the main filter caps are probably undersized for the 60Hz I was feeding it. The extra ripple would definitely appear as a lower rectified DC voltage on the DMM! Here's the updated schematics with the proper Magic Eye connections: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png

[@oscar_charlie]

Are we sure those two "diodes" aren't a kind of beam forming electrode like in a beam tetrode?

[@byterock]

Ouch bathtub oil caps. Just a word of warning many of these may of been made with PCB oil. So DO NOT, try and open them up to see what is inside. I will see if I can find that instrument in some old JAN catalogs I have. At first sight I think it was used for balancing signal outputs. Most likely for twin bean fire control radar, just a guess though.

[@teslakovalaborator]

at 600WV caps i don't think they do contain that sh*t, but a but of caution doesn't hurt. Maybe you can try to find a datasheet for them, if the type number is visible in the video and look if the dielectric impregnation is specified.

[@UsagiElectric]

Thank you for the heads up! Though, I have no intention of taking anything apart in this beautiful piece of equipment :) Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which seems like a fairly likely application, but it's designed in such a way that it could have had multiple uses on several different types of equipment.

[@cheater00]

Lovely explanation. I think starting the two diodes on the right, you messed up transferring the circuit to the schematic, because the schematic doesn't really make sense. Consider revisiting this part.

[@UsagiElectric]

Thank you so much! And you're totally right! I missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png This makes way more sense now!

[@cheater00]

@@UsagiElectric aye lol also you sire those diodes arent antiparallel? Thats what you do to clamp a signal on both sides

[@UsagiElectric]

@@cheater00 They are definitely parallel! The diodes have a shared cathode, and both anodes are physically connected with a little piece of wire as you can see in the video at 11:17

[@tomdchi12]

Resistor color band coding seems a lot less dumb when they're huge like that!

[@alexlang5308]

To me, it's an exposure meter for a positive process - in a dark chamber, only photoresistor is missing.

[@trevorhaddox6884]

It only measures AC input though.

[@UsagiElectric]

That's an interesting idea! Another commenter suggested that it was used as a Bearing Deviation Indicator in early sonar systems, which makes a bit of sense given that it's designed to give a more precise indication of incoming frequency. But, I think it was originally designed in such a way that it could have had multiple uses on several different types of equipment. Really, anything that needed a precise frequency indicator!

[@alexlang5308]

@@UsagiElectric It occurred to me because I had a similar exposure meter in the late 1960s. The only difference was that he was in a plastic box.

[@samehw8987]

about the magic eye tube it share cathode , so you have missing as you separated like two didoes, so all cathode should be to gather as original diagram in data sheets for all tube cathodes , so that's mean all base for the magic eye cathodes and diodes it's same cathode not isolate by 1MGO resistor as you showing in you diagram, more than the both diodes make the base for the control grade and balance come from the output amplifier to show signal level .

[@UsagiElectric]

You're absolutely about the magic eye! I double checked the wiring and missed an important connection from the magic eye's cathode to B-, here's the updated schematics: i.postimg.cc/jdZ7FfBh/Updated-Schematic-A.png i.postimg.cc/85MyR4K4/Updated-Schematic-B.png

[@abinaslimbu3057]

Ups Loptop (brand body)computer bisos prograamer mother bord(power cooler) Front pannal Retro q&a (Hanging physic)

[@terrydistance7823]

On the side of the case is a metal tag. It should have the NSN number on it. Naval Stock Number

[@UsagiElectric]

Unfortunately, the only tag on the entire case is the tag I show a close up of at 1:19 in the video, and there's no numbers anywhere on it. I sure wish we had a Stock Number though, that'd make it a lot easier to track down!

[@terrydistance7823]

@@UsagiElectric Oh sorry I missed that... great video, I love old tubes. Keep up the great work!

[@UsagiElectric]

@@terrydistance7823 Thank you!