Apollo Guidance Computer Part 6: Restoration update, a new sponsor, and a satellite launch

[@jeremybrown3139]

Hey, that was me X-raying the part. This was one of the coolest things I have ever been a part of

[@tesla242]

As an engineer I take my hat off to all of you, and also to the people behind the design of the AGC. Thanks for sharing this with all of us, to replenish our passion for electronics, engineering, knowledge and respect for the past.

[@LJDRVR]

What you guys are doing is absolutely sublime. I'm not an electronics guy, but I grew up with Apollo. When I go to work as an airline pilot, I'll spin up two laser ring gyros for my nav goodies, which are also updated by GPS. But unlike most airplane drivers, I know the history. So every time I turn those selectors to align, I smile and think of Stark Draper, and celestial nav and state vector updates and drift an gimbal lock and all of the giants whose shoulders I stand on whose, intelligence drive and resourcefulness make it possible for me to navigate all over the planet with hardly a second thought. And no Verbs or Nouns. Keep up the amazing work, you guys rock.

[@ElectricGears]

I know a lot of people resent the (comparatively) tiny amount we spend on NASA, but a huge benefit from all this early work being funded by the government is that so much of this technical detail is (legally) publicly available. This allows interested people to volunteer huge amounts of time do preserve it. No business would spend that amount of money. Plus, even if they knew nobody else would make a cent from it, I doubt most companies would be willing to sell it without layers of NDAs, if they would sell it at all at ANY price. Obviously not everything is preserved, but a lot is. Really ALL of it should be as we paid for the development. As much as we all probably love the work done by the private space companies, I have little hope that in 50 years we have any access to any of the early research/design/manufacturing information, even technology has advanced to the point that it has literally 0 commercial value. And did you say the simulated DSKY board was *10* layers? How the hell did that happen for an interface board?

[@Roflcopter4b]

Please do remember that the spending on NASA in the late 60s was anything but tiny. 4.5% of the US national budget is an enormous allocation of resources.

[@chrysopylaedesign]

In 2022, American Tax Payers funded NASA with $62 billion; ALMOST DOUBLE the COMBINED TOTAL amount spent by China, France, Russia, Japan, Germany, India, Italy, the UK, South Korea, and the EU. Again, ALMOST DOUBLE the COMBINED TOTAL of all other nations.

[@frequentflyer56]

Blue Danube Waltz. In my opinion the most classical and iconic space music ever composed from an era when space flight was just a dream for a very few and select people. Great use of this timeless classic Marc.

[@RonLaws]

I normally skip through sponsored mentions, but this time i watched it happily as it was appropriate, topical and constructive/helpful to the content of the video. so big thumbs up for PCBWay! Edit: Also one of the rare circumstances in computing where "If the connector doesn't fit, make it fit" is actually okay XD (not so wise in today's connectors)

[@SpinStar1956]

The reason the pins of the IC are 'splayed-out' is because the IC is meant to be used with an auto-insertion machine of which the end-effector relies on outward tension of the pins to hold onto the IC. So, the tension is always still there because the are not bent by the auto-insertion machine--just tension-flexed enough to line up side-to-side with the PCB holes. Great work and love your commenters!

[@AlainHubert]

Amazing work, both from this project and Mike's successful satellite launch. This is like watching a multi part riveting documentary ! Can't wait for the next episode. And a big thumbs up to PCBWay for the sponsorship ! That 10 layer board looks to be of very high quality. And I loved the Kubrick reference. In fact, the white on black silent title inserts reminded me of his style of editing. Thanks for sharing.

[@Banryu95]

The x-ray of the erasable memory is one of the coolest things in this project so far. I can't explain why... But troubleshooting those seems nearly impossible... But it's like those images gave an... X-ray of hope 😉

[@noelj62]

It's a huge restoration challenge indeed. Your team Marc rocks. It must be a very overwhelming experience to be a member.

[@carlclaunch793]

we do enjoy it - quite a lot

[@fridofridolin]

Give.....us.....more!!!!!! Awesome history in the making, and good humored too! I'm in all the way for the ride till the end. Make it fly again, boys!!

[@electronash]

Superb. This was like a mini movie. I could quite easily watch a 2-hour extended cut. ;)

[@Chriva]

You're everywhere, man :D

[@electronash]

@@Chriva It's what happens when you're quite heavily into electronics, retro computers, other nerdy stuff, and currently between jobs. lol

[@eloyex]

BETTER !!!! BY FAR !!!!!

[@jeremiefaucher-goulet3365]

Totally agree... I'd love the unedited uncut version.... Heck, I'd watch a live stream like Louis Rossman 🤩

[@SCP-POOL]

This is awesome! Thank you PCBWay!!!

[@tedvanmatje]

I wish every sunday would start like this: wake up, mug of strong tea, watch this video, scenes from favourite film, spacex launch.... Thanks, as always, for posting!

[@antronargaiv3283]

Very enjoyable. Can't wait for episode 9! The damaged writeable core is a bummer, but the FPGA artistry more than makes up for it. Ending up with a working Apollo AGC is going to be really neat. Also, many thanks to the owner and the sponsors for putting this effort together, and to Marc for some of the best KZbin video I have seen in a long time. You might also consider editing this together into a single long video and donating a copy to Smithsonian Air & Space and The Computer History Museum as a record of the restoration...you never know, someone else might need this information in the future.

[@CuriousMarc]

Don’t worry. They watch KZbin too...

[@foxdmulder]

This is the channel Nobel peace prizes are made of. To think that channels like this never feature on KZbin rewind demonstrates how humanity is lacking in creativity and the ability to demonstrate what we are really capable of.

[@mawsoncasey7347]

Way to go PCB way, never heard of you before but I have now and I will support your company for supporting this channel. Well done.

[@eloyex]

me too ......

[@theartist124]

Wow to see the _same AGC error codes_ from the Apollo 11 landing is really a nerd's dream, so cool!!!! 3:48

[@AlexisKasperavicius]

To get to touch and work on something so historically significant is quite a feat. I caught a look from the X ray operator that was like a nervous awe. What fun for all involved!

[@doalwa]

The best kind of content there is..highly entertaining and highly informative at the same time! You guys did a wonderful job!

[@MartenElectric]

Its getting better and better with every episode!

[@burningXtheXchip]

I want to build a relay computer. Even if its only a calculator. The work you guys do make me feel like I might do it one day if I watch enough videos like this. Please save every machine like this you guys can you guys are awesome!

[@Zone1242]

Best thing on KZbin for sure!

[@mspysu79]

Nice progress there, loved the 2001 bit :) Keep up the great work all of you!

[@XMarkxyz]

That "2001: A Space Odyssey" quote made my laugh so much, and this is an excelent video and work

[@lwilton]

I'm sure a lot of people will shout NO!, but I've had quite good luck cleaning up those old silver-plated military connectors like new using commercial liquid silverware cleaner. You want to use the liquid kind that works by chemical action rather than the scrubbing creme stuff. Just brush it on, wait a few moments, and wash it off with lots of clean water. Shiny like new silver pins.

[@SpinStar1956]

"I Wilton" you are correct. When I worked on the Hawk and Pershing missile systems, we used to use a clear-liquid silver-cleaner that had a pretty heavy smell to it and would form crystals in the bottom of the jar. We would then rinse the assembly in trichloroethane and then re-assemble them. The way I'd do it, is to first spray with Deoxit to form liquid fillets to the rubber-pin interface (to minimize silver cleaner going past the old rubber seal), then clean with the liquid silver cleaner you mentioned, finally flush with CRC-QD Electronics Cleaner and apply a fresh spray-coating of Deoxit.

[@jankais3r]

Hurray, another Apollo video!!! Thanks Marc and the team!

[@lenashou]

Ça faisait longtemps qu'il n'y avait pas eu de vidéos.. Mais je suis pas déçu, on passe carrément un cap là ^^ je m'attendais pas a autant de choses. Toujours aussi passionnant ^^

[@alpcns]

This is so impressive! Fantastic work on this fantastic equipment.

[@Chriva]

I see a Marc video, I give a thumbs up and watch it. I'm a simple man.

[@Carlos_Rodrigo]

Christian Ivarsson I did the very same thing !

[@eloyex]

If you watch and enjoy these videos, believe me, you are NOT a simple man !!!!!!

[@joeclarkey]

Fascinating. By far my favourite channel on youtube.

[@DieyoungDiefast]

After getting the AGC up and running, sticking a satellite into orbit is childs play.

[@DarksoldierX2]

I hope we get to see more videos like this!

[@grant2053]

Keep up the history making vids my dudes..... This kind of continuity on information is important for the future before these artifacts of rope memory and the other components break down... Thanks so much for ALL of your hard work... Been keeping tabs on the crazy old CS you guys have to use....

[@Wizardofgosz]

This video mark's (see what I did there? Marc's???) a change in your style. The segment with the 2001 music and the machining, and the actual SpaceX launch moved your videos out of pure documentary to something more artistic. We approve!

[@jeremiefaucher-goulet3365]

That 2001 Strauss Waltz sequence was simply golden... Had me laughing, beautiful, etc... Wow!

[@michaelcherry8952]

0:36 Why am I suddenly craving spaghetti? :) I'm really enjoying this series and I'm glad you were able to find a sponsor. You do realize that in order to fully test this thing, you're going to need a rocket, right? :) It's so interesting peering over your shoulders as you try to bring this to life. Looking forward to the next episodes.

[@bobl78]

I`m so deeply impressed anytime I watch these videos... I can not tell why but I`m so deeply impressed what they achieved back then.. thinking about what technology was back then... I`m working as an IT Administrator and we have 100+ servers... my systems move terabytes of data each day but does not impress me anymore because we have the technology available today... I know today´s systems are incredibly fast and makes a lot of things possible that the AGC´s guys could not even imagine back then.. but as I said, not as impressive as that stuff back then... I keep asking myself why I feel like that and I have no answer.. maybe because my personal opinion is that today many stupid IT solutions exist that we don´t really need and that ´do not get mankind ahead... I don´t know :-)These guys were making the basics that we still use today by watching these videos while sitting on the toilet Keep up the work, very interesting

[@eloyex]

this is bit level electronics ... almost electron level !!!!! many new engineers has no clue how to even get close to that detail. I used to program in assembler most of the time, and at some point i "read and talk" in binary while working .......

[@nicwilson89]

Man, I've been wasting my life... Great work!

[@oriole8789]

At least these were obtainable connectors from a series that's still active today. That's lucky! Lots of hardware from that era used connectors that have been long since phased out. Yours looks like 20-39 from D38999 Series 2, though I'm surprised by the solder contacts on the plug instead of crimped types. Modern aerospace stuff often uses high speed serial lines, which means twinax/quadrax/8-way/fiber... and all those connectors tend to be in the $1k+ range to buy, most of that cost being the high-speed pin groups; not to mention specialized tooling required for assembly. The actual connector shells are "only" $30-150. Future reverse-engineering of today's aerospace hardware will be a lot more expensive, even aside from the much higher complexity. Worse yet, a lot of advanced modern military hardware uses PCB-soldered filtered connectors (with LC filters for each pin), with the pins being non-removable in case of damage. But with a 20+ layer board, good luck desoldering such a connector due to the thermal mass. But, all this is part of our general trend of non-serviceable electronics unfortunately. Pretty much inevitable.

[@geneard639]

That was a more modern connector, you can tell by the Teflon back seal. That and the plating pretty much says its from the late 1990's thru the 2000's easily. I kind of wonder... MIL-C-38999's were used on the EA-6A's I wrenched on and the older versions had a spring clip holding its whole body together and removing it was. I had to mod a connector, popped off the spring clip and took the whole connector apart and used files to make it fit.

[@oriole8789]

@@geneard639 Hi Gene! I'm not familiar with older versions of these. I work with mostly D38999 Series 3's these days, but I'm familiar with other standards like M83723/26500/26482/28840/5015/etc. What I can tell you is that the "spring clip" you speak of is very common for all modern M83723 and D38999's to hold the plug body to the inner core/insert (this is still true today). The exact technique is up to the manufacturer. Amphenol/Deutsch/Souriau etc all use their own retainer and ratcheting systems. Souriau often uses a plastic cover over the spring clip. I've never seen a teflon back seal before though. That, along with the solder contacts suggests that this is either a manufacturer-customized version of D38999, or maybe not D38999 at all. Customized connectors based on a standard aren't uncommon. These days NASA has their own standards, such as SSQ21654 and others. Modern connectors are sealed with a proper environmental backshell, which would use a fluorosilicone ring to press against the area above the plug threading, along with another compression ring to create a seal with the harness. As such, any modern D38999 Series 1/2/3 + environmental backshell = IP67 rating when mated (and no rating when unmated). Also, have to be careful when machining the "olive drab" connectors (W/B designators), such as the one in the video, due to cadmium dust which is nasty stuff. EA-6A's are very pretty beasts. That must've been enjoyable for you! :) -Nick

[@tookitogo]

@@geneard639At 8:47 it looks to me like that might be a date code of 06/40.

[@daviddevillers6790]

keep up the hard work. truly remarkable efforts!

[@markhooper6786]

Absolutely awesome guys - amazing work!

[@carlklitzke9455]

Cool stuff man! I used to use a DAGE xray machine at my old job.

[@iwayini]

Wow, this is fantastic! Keep the video's coming please. Thank you very much.

[@TehWever]

Dammit Marc, you do keep us waiting.

[@lukealsmith]

I am proud that you guys are doing this :)

[@timthompson468]

Great video. I like the trick with the electric toothbrush application of deoxit. That could come in handy. There’s an interesting original video of the AGC by MIT Science Reporter on a channel called From the Vault of MIT, or something like that, if anyone’s interested.

[@infl]

get it because pcb platform wasn’t reliable enough... fr they’re smart as hell for sponsoring this

[@chrissavage5966]

Great work as always guys. Don't fancy trying to solve that writeable memory fault..... An aside, I hope Mike wasn't one of the many folk recently let go from SpaceX.

[@carlclaunch793]

Mike works for Capella Space, a startup that launches satellites. They used SpaceX to launch the satellite, but Mike remains happily (and busily) employed.

[@chrissavage5966]

@@carlclaunch793 Than you Carl, I hadn't realised Mike worked for someone other than SpaceX.

[@Broken_Yugo]

Would it be possible to isolate or piggyback the bad core section and simulate it with a small board hidden somewhere?

[@carlclaunch793]

That is one of several possible solutions. Stay tuned to see the options, investigations and solutions.

[@compu85]

Tape drives, fixed disk platters, and now military connectors.... is there anything that can’t be fixed on the mill? :)

[@Kajico]

I'm rooting for the core memory to some how be revived, even if it's a long shot.

[@TimoNoko]

You need telephone cable echo-locator for the broken line. Except faster and higher frequency than those used for kilometer long telephone lines.

[@shaunrossi9388]

You're looking for a TDM - Time Domain Reflectometer

[@RingingResonance]

@@shaunrossi9388 You could just use a good scope and a one shot signal generator at a high enough frequency.

[@Eo_Tunun]

This is Clickspring for electronics. ^^)

[@pandiatonizm]

My two most favourite movies in the world are Tarkovsky's Andrei Rubljov and Kubrick's 2001 Space Odessey, thank you for the An der schönen blauen Donau waltz pinpointing that

[@nameistunbekannt7896]

About time that you get sponsored.

[@eloyex]

for just one Chinese company ......... dont you think it is sad ?????? (by the way Thkx to that sponsor ...!)

[@stoobeedoo]

0:55 EMM - 2k words of core rope memory from 16 bit registers 1 word = 16bits (2 bytes). 2 * 2,048 = 4,096 bytes (4 kilobytes) of erasable core memory! It might not sound like much, but 4KiB of erasable core memory on something that small in the mid to late 60's was pretty amazing.

[@CuriousMarc]

Almost. I think you maybe mixing things up between core rope and erasable memory. Core rope was 36 KWords (of 16 bits), so 72 KBytes of ROM, and erasable memory (which is also core, but not rope, and has lower density) was 2 KW, so 4 KBytes of RAM. Which was indeed a lot for such a small volume (probably one of the highest densities achieved at the time), but an excruciating limitation for the programmers. They used every trick in the book to save a byte, including using a byte-interpreted higher-level language for complex calculations.

[@dmp0x]

lol congratulations on your 1201!

[@SomeGuyInSandy]

That X-Ray machine was amazing!

[@maicod]

I LOVE everything but your video editing @ 9:20 is superb

[@WillBreaksStuff]

Can you use a TDR to find the break? Also, great video, that project is epic. time division reflectometer, since you know the length of the wire from the X-ray.

[@gth042]

Mapping the capacitance at high kHz and comparing impedance of working lines might get ya close as well? You guys are tenacious -- true e-grit. Thank you for the videos, and best of luck!!

[@chrisscott1547]

I think you mean time domain reflectometer.

[@WillBreaksStuff]

Chris Scott yup you’re right. I use them so rarely.

[@TheLaurentDupuis]

This X-ray machine looks awesome.

[@dgaborus]

What kind of metal are those AGC instrument boxes made of? It is amazing how good state they are in after all these years.

[@macartm]

Fantastic to see another update. I can only hope that one day I get to work on something as interesting as that :D Maybe in 30 years time I'd have to do information archaeology on some Windows 3.1 system. Although by that point I'd be past retirement age and so unless it caught my interest I dunno if I'd do it ;)

[@macartm]

Or unless I'm skint and desperate for the money for the £50 it will cost for a loaf of bread then post-Brexit :P

[@koningbolo4700]

It's so bright Dave....

[@chuckpatten7855]

You might want to consider using a time domain reflectometer to see if it can tell you the position of the broken wire.

[@chutipascal]

Brillant le truc avec la fraiseuse et 2001!

[@typograf62]

It seems that you have fixed the AE-35 unit.

[@kevinreardon2558]

Thanks for this. This is beautiful. Speaking of beautiful, its nice to see such cute ladies at SpaceX C&C! When I was younger I went into Physics and was quite disappointed there weren't any women there. We really needed their kind of thinking.

[@knightfire2363]

You guys are AMAZING !!

[@herr_barus]

In which episode you will launch again?

[@markamcampbell6340]

can't wait for the next eposode.

[@DAVIDGREGORYKERR]

The owner of Frantone was trying to create the display panel for what you are working on.

[@StudioTV]

Amazing as always !

[@Lazarus7000]

That core module is not something I expected to see again, but I will say, as someone who prides himself on servicing non-servicable assemblies, I haven't the faintest idea of how to unpot core. Certainly any mechanical means are out, with the possible exception of carving off chunks before applying the chemical or thermal means, just to reduce the workload. Good luck!

[@Sixta16]

Depends on what it's potted in. Let's see what they will come up next.

[@sidewinder666666]

With (possibly a huge amount of) luck, it's a material that can be dissolved by a chemical solvent which doesn't *also* dissolve the other components of the assembly. I'm keeping my fingers crossed that's the case, just so an "original component" can be preserved and used.

[@nixxonnor]

This is awesome work!

[@MinhasA]

You are my new favorite yt channel :)

[@SusanAmberBruce]

Would it be possible to inject a signal into the erasable core memory block via the suspect wires, and analyse that way, like what the telephone company use.

[@adrianstoness3903]

could it be a bad Sader joint on that pin of the modual?

[@eloyex]

I am sure you know this. but I am gonna die if I dont mention it ...... a pencil style eraser do wonders with oxidized contact any type. IC, pins, plates, contacts ... and has a brush to get rid of the waste .... Is abrasive but not too much ... Always worked for me well doing this kind of archeology !!!! keep the good job engineers ..!!

[@grhinson]

Can you do a distance to fault test on the module?

[@johnnndoeee674]

Great vid any more vids coming on this ?

[@spunkmire2664]

i got nervous at the machining of the mass connector. haha

[@rotareneg]

If the break in the wire is narrow enough I bet you could weld it back together by applying enough voltage to arc across the break. Not sure if I'd actually try it on something that's as irreplaceable as that memory module though.

[@CuriousMarc]

We thought about it, but the wire is so tiny (4 mils) that I think it has much many more chances to just vaporize rather than welding. We could get 4 mil wire and try it in an experiment.

[@Uvisir]

that giant FPGA hack was insane!

[@Digital-Dan]

Feels like a millennium's progress in 60 short years.

[@JuneNafziger]

Dan Swinehart moors law is amazing

[@eloyex]

9;13 ......... yes, you are the kind of guys capable to save the Apollo 13 too, again .. if needed !! hehehehe ...

[@rearspeaker6364]

someone call gene krantz!!!

[@bobl78]

how does the rope simulator work ? "Normal" RAM Chips inside that need the Contents loaded into before simulating it the AGC ?

[@carlclaunch793]

Yes, but they have only the room to hold one word of the 36K at a time. The contents are requested by the rope simulator over the connector we were fixing. Ken's driver box, a Beaglebone with a custom cape on it, will take the requests and feed the one word to the simulator. The simulator latches the 16 bit address set up by the AGC, asks the external box (Ken's) to send it a word, then when the read pulse is produced by the AGC, the rope simulator produces the pulses that would be returned by physical core ropes, corresponding to the one word being requested.

[@Sixta16]

What for do you need 10 layer job for a simple display interface O_o

[@BlackEpyon]

It's not like modern displays where everything is multiplexed on a grid array. The DSKY had a relay for EACH individual element especially for the electroluminecent (no LEDs back then) 7-segment displays running at high voltage, a large pin array header on the back, and a bird's nest of wires in between.

[@carlclaunch793]

It includes 23 logic interface circuits for shifting 28V logic down to TTL for the Arduino, 9 relays with driving circuits to output 28V logic based on Arduino 5V signals, 21 seven-segment displays, hundreds of LEDs. The major constraint is the small DSKY box and the specific placement required for each light and display in order to look like the DSKY. That made routing quite difficult - impossible with the standard Designspark trace sizes and separations even at 10 layers. There is a 5V power plane, a ground power plane, a 28V power plane and a switched 5V power plane for the many LEDs that have to switch on or off based on the switched 14V power line coming from the AGC (for standby mode).

[@Foreseeable1]

SIP connecters as well as Dram chips and heat creep, dem were the days

[@USWaterRockets]

I love this series. One thing I would like to know is a bit more technical details about the core-rope emulator device. Those "DIP-stick" assemblies don't like very complex, so I was wondering what is in there. It seems like it would have to be some kind of static RAM or something. Which begs the question, if SRAMs were available at the time, why did they use core-rope memory???

[@carlclaunch793]

At the time that the AGC was designed, a 16 bit memory would take 16 chips to implement. To create a 36K word memory for programs would have taken a half a million chips, more than 10X the size of the AGC. The core rope is a read only memory, not a RAM, with an very important objective of keeping the programs from being corrupted by errors or other failures. The core-rope memory is driven by the AGC with putting an address on certain signal lines, then pulsing the memory to read. The simulator captures the 16 address bits, sends a message to an external computer that was hooked to the simulator. The external system had large core memory inside it, loaded from a tape drive. The external system sends the 16 bit word back to the simulator box. The simulator box has enough storage for the 16 bit word, which it provides to the AGC when the read control pulse is sent by the AGC. In other words, the simulator boxes look at the address coming from the AGC, ask an external system for one word, then turn that one word into appropriate pulses into the AGC at the right time. The core rope simulator boxes have the ability to store the 16 bit address, to send those over the cable to an external system, to receive and hold a 16 bit word, and to produce pulses at the right timing to convince the AGC that the word value was read from core rope. We don't have the external system that was hooked to these simulator boxes. We don't have the schematics for the external system. Ken is engineering an external system, using a Beaglebone controller and the cape PCB he built, which will look just like the external system to the simulator boxes. The boxes will think they are talking to the external system. Ken had to reverse engineer the insides of the core rope simulator boxes, plus analyze the memory reading logic in the AGC, so that he could design and program the external system which we will use to drive the core rope simulator boxes. His Beaglebone system will hold all the various core rope software versions that have been found, allowing him to choose one which the AGC hardware will execute when we power it on.

[@USWaterRockets]

Thanks for the explanation. Calling it an "emulator" was throwing me off, as this implies that the box itself was emulating the core rope memory itself. I don't recall the video mentioning that it translated to an external memory, which was missing. That's why I thought it needed to have memory inside. Now it makes a lot more sense.Given the way it works, it seems like even if the emulator was broken or was never even found, that the functionality of the emulator could have been reproduced on a new design. Imagine taking the beaglebone and probably a bunch of comparators or level shifters to sense the inputs of the core rope interface and then output the correct levels in response. Put it all in a nice box with a USB interface to connect to a PC to load the programs. This is how I always imagined it would be done, since the emulator didn't seem to be documented. Thanks again for taking the time to explain the emulator to me.

[@carlclaunch793]

@@USWaterRockets The AGC is not sending logic levels nor latching them in. It believes that it is hooked up to actual core ropes. It sends hundreds of ma of current in a short pulse to cause the large core to flip. The sense amplifiers are watching a differential wire pair to detect any kind of low level pulse that returns if the sense wire is woven through the core. Thus, to replace the simulator boxes themselves, we would have to match the impedance and characteristics of the core rope, absorb the current pulses, then produce a return millivolt pulse at the proper time to cause the AGC to see it as a one bit. The driver circuits inside the AGC are kind of sensitive - if they are operated with no rope module installed, the power transistors blow out. If they are connected with a simple short circuit, the power transistors burn out. The connection must be within the range of real core rope to suit the driver circuit. This is why it was useful to reverse engineer the core rope simulator boxes. They do the heavy lifting, presenting the right impedance to the driver circuit, converting the pulses into a logic level to determine the address request, and produce a plausible millivolt level pluse for the sense amplifiers for any 1 bit that is being read. The round connector side of the core rope modules, on the other hand, operates with regular TTL logic levels, not pulses or analog stuff. That is why Ken chose to drive them instead of replacing them.

[@USWaterRockets]

I was not aware that the driver circuits would blow if open or shorted! I can see why getting the emulator running would be desirable. I do wonder, has the emulator been reverse engineered to the extent where schematics have been created for it? Seeing how there were so many issues getting the DIPs to simply make a connection inside the DIP sticks, I would be nervous about a connection in the emulator being faulty and causing the damage to the AGC you warned about. Perhaps the DIP devices are not in a part of the circuit that is critical that way, but I suppose you already have determined that everything will be safe. Thanks for the detailed response!

[@carlclaunch793]

@@USWaterRockets The core rope simulator boxes use analog transformers to present the proper impedance to the AGC driver circuits. Ken has reverse engineered it to the level that he has a schematic. I will check to see if he will post it for others to view.

[@FesixGermany]

Lovely video as always.

[@adamsnook9542]

Awesome! Now you just need to get a few peripherals hooked up and you'll be able to fly to the moon.

[@vibrolax]

I know where you can find a complete Saturn V.... There's also an unused Apollo CSM flight artifact... Have to build a new service structure for the launch pad... You can just push SpaceX's stuff aside to do your launch. Make a video, or no one will believe you.... Well I guess everyone will hear you launch.... Not sure any lunar module flight artifacts are left...

[@JaseCJay]

6:50 71 pin connection for Nintendos..

[@SixWildKids]

Where is trichlor when you need it?

[@cptcrogge]

Good job!

[@KirkIsmay]

Would it be easier to try to borrow a memory module from another AGC?

[@CuriousMarc]

That would be way easier. Do you have one?

[@KirkIsmay]

​@@CuriousMarc no, sadly. I was thinking about the one at the Computer History Museum: www.computerhistory.org/

[@warsstar]

9:09 Glorious !

[@douro20]

Just try not to run up against the Chinese New Year when ordering boards... In other satellite news, DIRECTV has recently announced that they have launched their last satellite.

[@cpt_nordbart]

Another Great Computer!