Wonders Inside A NASA Apollo Era Digital Panel!

Update: Since publishing has come to light that this panel was used as part of the testing apparatus for the Apollo Guidance Computer. Further study is required....
This has been in the queue for a long time but it was worth the wait! Such an amazing piece of space history - from the support equipment that was used to build the Apollo Command Modules at North American Aviation in Downey, California back in the mid 1960's. Enjoy!
LVDC Logic Devices - www.frantone.com/designwriting...
0:00 - A look around the outside
2:20 - Opening up the top
3:30 - A very tiny module!
5:00 - More inside
6:50 - Opening the bottom
7:35 - Removing a One Plane Display
8:15 - A look at the Display Decoder
10:00 - Looking at the other displays
12:12 - Cool Power Switch!
12:45 - Removing a Module
13:00 - Inspecting a mini DTL gate
15:05 - Thanks and Top Patron Credits
Join Team FranLab!!!! Become a patron and help support my KZbin Channel on Patreon: / frantone
#franlab #NASA #AGC
- Music by Fran Blanche -
Fran on Twitter - / contourcorsets
Fran's Science Blog - www.frantone.com/designwriting...
FranArt Website - www.contourcorsets.com

[@frankowalker4662]

What an absolute work of art. The design and engineering that went into it is stunning.

[@EEVblog]

Wow, love it! I would have guessed a fair bit later than 1964. They probably only made a dozen of these.

[@FranLab]

Or less even - of this one configuration. But you know the first rule of Go Fever - why make one when you can make 20 at 30 times the cost!

[@perwestermark8920]

@@FranLab The chaining feature of power and I/O and what looks like a rotary switch for setting an unit address indicates that they expected as many units in series as that switch had steps. And then also that the power connector must be able to handle the power to all units following in the chain.

[@absurdengineering]

@@perwestermark8920 Yep! This looks like a numerical register I/O type display where you could display a value and change it. It made sense to daisy chain them to make it practical.

[@ericfielding2540]

Amazing amount of careful work to build this, to only display a few numbers. It was so much easier only a decade later.

[@CARLiCON]

serial number 130

[@ahclemtube]

Fran. I have a 1964 TEC lite Data Panel catalog PDF with the transistor bulb on page 9 and a bunch of pages at the end to allow you to design a custom panel. It seems that most of those lights were special design. I didn't want to just send it to you as you wouldn't have known what it was about and might have trashed it thinking it was a virus. Let me know if you want to see it. The catalog is worth it for the artwork alone.

[@-jeff-]

Fantastic workmanship from a time when things were built to last. TY for the this great teardown!

[@dennisyoung4631]

“…. because the consequences of failure are so dire…”

[@davelowets]

The components were built to last, the technology not so much.

[@porticojunction]

Your descriptions are much better than mine would ever be. "The thingy on the thing with the stuff and junk". Thank you for the tour, old explicit components that are built like tractors are so fun.

[@J0hnSell]

It’s absolutely incredible seeing the craftsmanship of these NASA units from nearly double my lifetime ago and the boards look cleaner then anything today!

[@liam3284]

NASA was among the biggest customer, paying top dollar. Suppliers could afford that level of quality.

[@SeanBZA]

Those hermaphrodite interconnects are from the phone industry, and were common on phone boards to enable the field technician to replace the line conditioning circuit on phones, so you had 3 modules you could plug in, that gave different amounts of side tone and gain for old 1970's era phones. They had 3 of those on the phone board and 3 on the module, with the plastic box having some resistors and capacitors on a small PCB, so you had low gain for short phone lines, medium gain for longer and high gain for long lines, so the audio was always constant level into the exchange, and sidetone level was also varied so the line would not be overloaded. The lamp units use the same bulbs as the display, and there are various types, all with the same pinout. Some have a transistor buffer, designed as a sensitive driver, others have nothing just the lamp connection, and the unused pins are to use as terminals for other functions, and then you have some with a built in self test switch in them, that use a separate supply, and allow you to press the lamp to test it, and also have an output that allows the press of the lamp to do a lamp test for all the display units as well. The self test disconnects the internal input, so you do not feed voltage back to the driver. All in the same package, and I actually have one or two salvaged from old equipment somewhere.

[@gcewing]

I think I've found a manual for this! Googling *apollo "c-start"* gives me a link to a PDF titled "Operator's manual, Acceptance Checkout Equipment". Seems it was used for sending commands to the AGC during testing. No schematic, unfortunately. You might like to contact Curious Marc, his team seems to be good at finding Apollo documentation.

[@GotYourWallet]

So they didn't use in on the spacecraft itself. I was wondering how they would have such heavy duty construction on a weight limited mission.

[@olddisneylandtickets]

This was a fabulous look at this very well built device, even the bulb was elegant! More yes please....

[@mnoxman]

There is a strong possibility that Seymour Cray had a hand in engineering that considering it was made by CDC. The "cord wood" construction of the decoder is classic Cray. It was used on the Cyber 6600 and 7600 series. On YT there is a old PACE video on how to solder turrets "Basic Soldering Lesson 2 - \"Soldering To PCB Terminals\" " . Turrets are a brioche to solder/work with. FWIW: I see a white wire that was clipped on the side with the fuse.

[@keithyinger3326]

I'm glad you end up with some of this cool stuff to show us. Some other KZbin channels would be drooling over all of the gold connectors inside of there. I know it's more than likely never going to work again or actually do anything functional, but it is still neat to see that old stuff like that intact.

[@jimmy_jamesjams_a_lot4171]

One small step in the evolution of PCB manufacturing. One giant leap into Fran’s kludge box!

[@rustymotor]

Pure quality! Everything hand soldered and wiring harness done by hand, reminds me when I was doing my apprenticeship as an instrument fitter (1980’s) and assembling control cabinets for a power station. All the wiring was connected and bound using a type of wax string, no cable ties. Wires had to be run parallel together and tied off, any mistakes found and then all the harness string cut and then redone. It certainly looked neat and tidy once done, not like some data comms rack cabinets you see today!

[@journeymanAmp]

The product of a Golden Age of electronic assembly. It may be obsolete but it’s stunning!

[@ericcarabetta1161]

It's so weird looking at ancient electronics, since they look so professionally made and well done, yet so "homemade" looking at the same time, because of the size of the components and circuit traces.

[@John_Ridley]

My guess would be that the big rotary switch sets which unit in the display chain this is intended to be. It seems like these are intended to daisy chain both power and data so that would make these replaceable modules.

[@perwestermark8920]

Yes both power and I/O seems to chain so it's logically that the set the unit address with that internal rotary switch. A bit like uo to 16 SCSI disks chained on a cable and you had to assign an ID to them normally using jumpers. And the total number of possible units to chain is the reason for the heavy-duty power connector since it also needs to power all following units.

[@DanielBull]

That was exactly my thoughts. A rack full of them daisy chained and this sets the ID

[@SamiJumppanen]

When opened, I was saying exactly the same: "Oh, wow!" Watching from screen, HD projector, I think the 60+ inches from 9 ft gives a nice perspective into zoomed in electronics!

[@georgenaha1001]

The beautiful wiring put me in mind of Mark Bartel's guitar amplifiers. Mark started the Tone King line of amps years ago, and now runs Bartel amps. His work is quite fastidious and visually stunning - and the amps sound great, too. :)

[@mrtnsnp]

I wonder if Curious Marc and team could use this in some way in their Apollo communications series.

[@torenarend]

This screams "COLLAB"

[@peteb2]

And here you go Fran, i am at work on a break & watched this whereupon a group of other young engineers have wandered in & immediately stopped to watch this incredibly informative insight into this tech. They all simply do not believe this level of semiconductor style designed equipment was at work like this in the early/mid '60s.. "But everything was tubes in the 1960s" was one comment....

[@tomgeorge3726]

Does Curious Marc, know about this console? The internals, great workmanship.

[@zeroequalsthree8649]

Something about those wee modules... So cool.

[@tvtoms]

That was a cool look into the tech of the era. Super high tech indeed for the time. Those split spade cross connections (or whatever) were really fun and the macro version of micro circuits on them just pure gold.

[@sgtellioman]

Your skills with electronics are clearly evident. Nicely done.

[@fartraveler3345]

Brings back a lot of memories. Thank you Fran

[@curtwuollet2912]

I did a stint at CDC government systems in about 73. And that's the way things were done, certified solderers and all. It was the start of ICs but many things were still discretes.

[@mikefochtman7164]

Yeah, in the Navy back in the early 70's they had a two-week school for 'soldering' and such. We spent about a day just learning 'turrets' and other days learning specific tasks, like proper lead formation, board soldering, attaching wires to 'pin cups' (the little hole on the back of connector pins to insert/ solder leads. Of course now over 50 years later, I probably couldn't solder onto a turret in less than an hour. lol

[@curtwuollet2912]

@@mikefochtman7164 I'm afraid cable lacing is a lost art. I've still got a roll someplace.

[@mikefochtman7164]

@@curtwuollet2912 Yeah, I have some waxed lacing somewhere still. We had one fellow that could do up lacing that looked like he measured with a ruler between loops, it was soooo... pretty. ;)

[@curtwuollet2912]

@@mikefochtman7164 I quit building automation about 5 years ago. One day my boss asked me why I always used those crazy round connectors. I told him millions of dollars were spent making sure those connectors stay connected.

[@roberthoople]

At first glance it may seem somewhat crude to our super-fine multi layer precision PCB's - with screen printed graphics - that we have today, but then you look closer at that edge soldered module and the painstaking precision, layering and complexity that was done by hand here, and this stuff truly is a Master's work of art.

[@safetyharborfirearms]

Keep 60's space race gear coming ...thats how I found your channel

[@UpLateGeek]

We still do cable lacing on the backs of our vision cable patch panels at work, and our cable installations are pretty awesome. But our engineering and maintenance departments don't design electronics anymore. They do the occasional repair of gear, but that's becoming less and less common and involved, since most stuff these days isn't really repairable. They can swap boards out if replacements are available, and they can calibrate and tweak them, but not much more. Most of the maintenance department's time is spent repairing broken connectors on cables and equipment, or building custom cables/harnesses. The engineering departments tend to just work at the system level, rather than component level. Think port X on box A plugs into port Y on box B. I made the mistake of showing off some pictures of my (hobby) electronics projects, and the engineering manager has been threatening to get me to design custom electronics for them. I would love to do it, but I'd also love to have the time to do it. My actual job needs more hours than I can give it and maintain a reasonable work-life balance, so I can't exactly take a couple of weeks off to work on a project for a different department.

[@matthewmiller6068]

I wonder if CuriousMarc has a manual that explains what that is or does inside...he seems like he will be launching a whole re-created saturn 5 and Apollo lunar mission any time now

[@brooklyndrive]

Thanks Fran!

[@nomanmcshmoo8640]

Thank you, Fran! I work in Space and Defense and lemme tell ya, it is amazing how much stuff from this era is STILL ( I kid you not) operating. I can only imagine how much has been discarded over the years. I work on a lot of test consoles from this era frequently and they are a MARVEL. Many are just finally starting to fall apart and many are held together with chop sticks, dental floss and Wrigley's chewing gum. It's amazing how TOUGH a lot of this equipment was. Your videos actually help me do my job well and I appreciate all of your efforts to educate people on Apollo Era technology!!!!

[@davba2]

I’ve come across those forked pins before. If you’ve ever used EDAC or ELCO connectors, they used the very same pins. They were used extensively for professional multicore audio applications.

[@TheErador]

I hate edac with a fiery passion

[@morkmon]

Incredible, thanks Fran, great video

[@rippenbug]

I recognize those bulbs with the fresnel lenses, the bulb is probably a 327, it pulls out of the back of the lens, and those look like lit push switches.

[@TehMG]

Yup, definitely a lit push button. I actually have some very similar lamp/switch units in my stash. Two pins for the lamp, the other 3 for the SPDT switch, C, NC, and NO contacts.

[@MikesArcadeMonitorRepair]

Amazing. Thanks for sharing this.

[@InssiAjaton]

We used for a year or two those hermafroditic connector forks. They appeared fantastic, but they required more tender treatment than what some of our guys were accustomed to. I seem to recall our vendor was Elco, or maybe Elcon (?). They handled a good amount of vibration, but a slip to the side, and the fork stopped making reliable contact any more. I guess the people trained for NASA work were trained much better. Then a second comment (although only one was asked for!). Fran, if you have not been noticing, or dealing with Curious Marc, you should. Like some other comment already mentioned, he seems to be re-building the whole communication system for the Apollo system.

[@thewatchworks1372]

Electronic artistry at its finest!

[@maxeisenstadt1459]

Amphenol connectors! Classic military equipment. Love the little flyball-esque circuit modules.

[@DoctorCalabria]

Hi Fran! Looks like a Welch Allen bulb that we use for otoscopes. This looks like the kind of thing I’d find on Canal Street in the 70’s. You are amazing!! I’ll reach out to you soon if you’re up to it. 👍

[@barrydevonshire9749]

I used to lace wires together in the the early years in the industry. So much tydyer than tie wraps !!

[@wirdy1]

Seeing you describe the lacing on those looms makes me feel old; I did that stuff on avionics LRU's from the 1980's.

[@simontay4851]

You should send this to CuriousMarc. He and his team would be able to get this working. Master Ken could easily reverse engineer the circuit.

[@discreetfire]

Damn, I love teardowns! Thanks, Fran!!! I'm upping my Patreon! I now love electronics because of you!

[@k.kristianjonsson1537]

The happiness of fiddling unknown things apart.....................................

[@gannas42]

Good ol' Control Data. Nice to see my home town represented in some of what has to be the coolest tech from back in the day! Thanks for sharing this with us. I wish it could be powered up.

[@fazergazer]

Brings back fond memories❤

[@ryanreedgibson]

Wow looks like a more complicated XLR balanced audio adaptor. I bet that device would run for centuries!

[@Chiavaccio]

👏👏👏👏 great video!!

[@rickharold7884]

Super fascinating Thx for sharing

[@jdog987]

This may be a device in which CuriousMarc and his team can help you with, especially in the connectors department.

[@TheJoeyboots]

I liked how those numbers looked.

[@uncletacosupreme7023]

Wow this is so cool.

[@ijasmohamed5909]

This video need millions of views

[@JohnVance]

Very cool! I had no idea the “J” designation for connectors went back that far

[@brendakoldyk1647]

j stand for jumper wire.

[@JourneymanRandy]

Very cool.

[@theelmonk]

That first module you pulled out reminded me of logic circuits we played with at school. It might be a discrete diode-transistor logic gate. I thought the bigger one would be a flipflop but since the transistors are different it might just be a 2-stage lamp driver. It would be interesting to trace the schematic of those modules out.

[@Broken_Yugo]

Yeah, definitely looks to be mostly DTL.

[@iramoser3528]

Super cool! Gotta love the serious construction of the thing. Surprised the chassis was cast aluminum instead of sheet metal. The little logic modules were neat, as well. You can see why so much of this stuff was scrapped for precious metals recovery.

[@joeteejoetee]

The lamps have 2 Patent numbers printed on the body - that would be a great place to start learning what's inside of them.

[@johnpenner5182]

the hand-wired prototypes of Integrated Circiuts! cool!

[@ReedCBowman]

What a cool find. And a great exploration of it. There ought to be a term like 'unboxing' for this kind of breakdown and study of fascinating old tools. BTW, 'Fresnel' is pronounced 'freh-NEL' with no 's' sound at all.

[@SpydersByte]

have literally never heard anyone pronounce 'fresnel' without the S lol

[@themanwithnoname8241]

@@SpydersByte Is that because you're an ignorant American?

[@algiefeatherstonehaugh1091]

@@SpydersByte He's right.

[@TheErador]

@@SpydersByte wow. Hit up your friendly local theatre tech, and see if they say it right!

[@xAEROPLANEx]

@@SpydersByte A Fresnel lens (/ˈfreɪnɛl, -nəl/ FRAY-nel, -⁠nəl; /ˈfrɛnɛl, -əl/ FREN-el, -⁠əl; or /freɪˈnɛl/ fray-NEL) No 'S' sound, it's in the middle of a French name.

[@newportshapwick]

Great video! Brought back lots of memories. What craftsmanship in those days - puts most modern stuff to shame - beautiful and elegant design and construction. Spent many a happy hour lacing wire harnesses. I remember the hookup wire we used for the looms was PTFE coated silver core (or maybe just coated) wire. I wonder if it's the same in that unit?

[@Astroponicist]

Hand fabricated craftsmanship like that just isn't seen today.

[@soniclab-cnc]

fascinating stuff...

[@standarddeviation6428]

Fascinating!

[@markedis5902]

We were still making things very similar to that in the 80s for the MOD

[@aaronwong2773]

Thanks.

[@anthonymiller8979]

My grandmother worked for Bendix here in Baltimore in the early 1960s and her job was soldering components on boards like these.

[@gabrielestefani2950]

Just yesterday I had to study DTL inverter in detail. That has just one transistor, so this could be another logic gate, maybe NAND or NOR? Really cool

[@zaprodk]

That's some absolutely beautiful construction. I wonder why the choose to make all those small plug-in modules instead of integrating it all on a single board.

[@UdderlyEvelyn]

Presumably easier to repair and/or reconfigure?

[@SeanBZA]

Made so you can test all the modules before use, and test the board itself as well, and after assembly it makes troubleshooting easy, as no tools are needed to replace a failed module, just grab another tested module, plug in and get running again. Very important if you have a fixed deadline, like a launch window, and the equipment has faulted, and you need it running now, before that window is closed and you need to scrub the entire launch till the next window opens up, possibly in weeks or months, or even decades.

[@absurdengineering]

Compared to today, back then transistors were “junk”. They didn’t last long and were easy to damage by heat of soldering, the process contamination and poor process control was often an issue, etc. Having those modules easy to replace was critical to uptime. Otherwise you’d expect to be doing lots of soldering over the lifetime of that device. And imagine if they had 6, 10 or 12 of those in a chain. Major pain to fix if it took anything more than identifying a failed module and replacing it.

[@mikefochtman7164]

That lamp with the lens that you unscrewed (about 11:30) has a replaceable bulb in the end. You might not have noticed, but there's a flange there and you can pull the bulb out of that 'holder' assembly. We had some units very similar and getting the bulb out sometimes takes a sharp blade to wedge between the threaded assembly and that bulb's flange. But our units only had two wires, not five. That's a puzzle. I spent a couple of days in a Navy school learning how to properly solder onto those 'turrets'. Lots of old equipment had them, mechanically wrap the wire(s), being careful to get at least 270 degrees of wrap, but less than 360 (that in itself was a skill that took a while to master). Then apply solder. Never saw the pin hole on the end type though. BTW, love your videos exploring those old bits of technology.

[@danielkochanicek6906]

Those tongues how you say...i have actually never seen something like this nor thought about it not single time....wow...i am shocked....i just love those old days electronics .... genious ! :)

[@speedshopnetwork]

Man I would love to poke around in some vintage NASA gear!

[@CARLiCON]

I tried posting this before but it wouldn't let me probably because I included a link. It appears to be from the MSOB ACE-SC control rooms "Control panel with one C(Computer)-START module. A C-START module had ten 12-position rotary switches. With each switch one out of 12 characters (0 through 9 and the "+" and "-" sign) could be selected . This C-START module was used to call up command computer test subroutines and to enter data as test parameters."

[@FranLab]

It will have to get powered up at some point in the future...

[@1969fallen]

Nice video

[@DrJaneLuciferian]

I love those cruciform pin connectors. I've never seen anything like that before. Very cool :^)

[@marvintpandroid2213]

Sees the title, this will be good

[@bassmandanmartin3700]

That was awesome!!! 💖💕💖💕💖

[@WJV9]

Those posts on the back of the displays are solder posts, wire wrap posts are square with sharp corners and solid wire was wrapped around to create 4 gas tight contact points per wrap. Typical 3 to 4 wraps required per connection. The displays are one lamp per digit 0 - 9 plus/minus and decimal point. The 7404 are not TTL logic chips, those are transistors.

[@robertoguerra5375]

Great video:) Maybe there is more information about those mystery bulbs, by looking up the patent number

[@michaelodendaal5776]

It's so beautiful 😍

[@brendakoldyk1647]

Fran those lights that you took out are push button switches. I have some of those in my part pile. Nice video.

[@DrJaneLuciferian]

With the lamps my guess is they have lamp test functionality built in along side the indicator input so usage and test can be implemented completely separately.

[@CT-qx8nl]

When I seen the way you handled that screwdriver, i knew you were a really one!

[@triplea25]

Very kewll stuff.......

[@benhetland576]

I had a go at reversing that 2035 PCB you showed in detail, and it appears to be a 3-way AND gate. (Maybe that's what the T3 designation hints at?) The connector on the "interior" of the board (not along the edges) is GND and the 3 pins around it are the inputs. Power and output on the corners by the transistors. Somebody probably has the pinouts and types for the transistors, but my guess is the S7409 is an NPN and the S7324 a PNP.

[@byteborg]

Perhaps @curiousmarc has some insights on the use and system connection of this thing, as he does this great series on apollo radio equipment.

[@mostcom]

@ 8:33 those lamp contact springs will be silver plated then coated with a dielectric spray to prevent tarnishing.

[@LightSoySauce]

awesome

[@andrewadkins5567]

It looks like you opened Pandora's box. A simple appeating display turned into a wonder land.

[@marekpo78]

WoW amazing part of historii 👍👍👍

[@BrianBoniMakes]

I like the Fender amp knobs. Wasn't made too far away from Fullerton.

[@VictorianMaid99]

I just seeing this old technology!

[@Skunkola]

Thats pretty sweet

[@jamanjeval]

3- 18. C START MODULE OPERATION. 3-19. The C START module contains ten 12-position rotary switches, ten projection- type indicators that indicate verification of switch position, also verification indicators, power on lamp, and an XEQ/SEAL pushbutton switch. This module may be used to cail up and modify Command Computer subroutines, and to supplement the data stored in the com- puter memory. 3-20. The C START module is used by the operator to call up a test control subroutine and enter test operation parameters into that subroutine. These parameters can cause the subroutine to: a, Enter time controlling the start and stop of an analog function. b. Enter time interval controlling the time between discrete steps of an analog function. c. Vary the frequency and amplitude of an analog function. d. Enter time controlling the start and stop of a sequence of switching events. e. Enter time interval controlling the time between each event of a sequence of switching events. f. Institute a prestored sequence of switching events or analog functions. 3-20. The C START module is used by the operator to call up a test control subroutine and enter test operation parameters into that subroutine. These parameters can cause the subroutine to: a, Enter time controlling the start and stop of an analog function. b. Enter time interval controlling the time between discrete steps of an analog function. c. Vary the frequency and amplitude of an analog function. d. Enter time controlling the start and stop of a sequence of switching events. e. Enter time interval controlling the time between each event of a sequence of switching events. f. Institute a prestored sequence of switching events or analog functions. 3-21, For example, assume that a subrou- tine contains a sequence of instructions to be performed on capsule internal pressure. Further assume that the subroutine contains all the instructions and data necessary to perform this sequence with the exception of the upper and lower pressure limits of the capsule. These limits could be entered into the C START module and combined with the instructions and data in the subroutine to produce a complete sequence of test opera- tions in the test bay, 3-22. During normal operation, command data is entered in the C START module (figure 3-3) by properly positioning the ten rotary switches. As each switch is posi- tioned, the projection indicator above that switch indicates the character selected by that switch. (The characters include the digits zero through nine, a plus sign, and a minus sign. ) The projection indicators are then compared with the switch settings for correct command entry. After the command has been entered and visually verified, the XEQ/SEAL switch is depressed, causing the upper half of the XEQ/SEAL switch to light. This may or may not be visible to the opera- tor, since the switch remains lighted only as long as the command is onthelines. Whenthe command has been processed, the computer will send a verify signal to the module which will illuminate the verification indicators. 3-23. The verification indicators (located directly over the XEQ/SEAL switch) indicate verification of commands as they are entered and processed by the computer. The specific pattern (or combination) of indicators which light to denote a verification is a function of the computer program. To illustrate a pos- sible application of the verification indica- tors, assign a binary numeric weight to each indicator: upper left 1, upper right 2, lower Left 4, lower right 8. Assume that the.com- puter program is written so that the 4-bit data word entered by the rotary switch on the extreme left end of the C START panel is verified. Setting the left-hand rotary switch to 5 will cause the corresponding verification indicators to light upon processing of the entry by the computer, specifically the upper left (numeric weight 1) and the lower left (numeric weight 4). Usua1ly, however, all four lights illuminate to indicate verification, and different light combinations are used to indicate various command errors. From ibiblio dot org slash apollo slash Documents slash ace-sc_operators_manual.pdf Page 3-15

[@quantummandavid]

I love you Fran

[@tempesttempest769]

🤭

[@-r-495]

12:09 the unusual lamp.. maybe there‘s a feedback circuit that detects a broken filament?

[@piwex69]

They went to town with this molded case. The holder "platform" for switch/pot reachable only from inside seems to be a very fixed fixture. Like for other uses it would be there too !?

[@FranLab]

Custom cast just for this module I would think. But a multifaced high resolution sand casting is still very difficult to do - I am sure they had many reject castings.

[@mostcom]

In the mid-70s the FFA replaced ALL or their RADAR equipment for the North East United States Control facility. Well me and about 20 other teenagers had a field day with about 25 or so standing cabinets of the most durable electronics equipment of the post WWII era. Millions worth. For example the smallest coil filters were housed in zinc chromate primered with olive drab painted cans, that had printed schematics on them. Don't ask about the tubes, rheostats, big old selenium rectifiers. The synchronizer cabinet was the most awsome.

[@Danielallanz]

The frist board you pulled looks like some kind of Darlington configuration..(6 pins)....would make sense given that this era is germanium semiconductors with low hfe gains..