Apollo DSKY - part 1: we have a real (and broken) DSKY!
Hello and welcome back. If you follow the channel, you know that we restored an Apollo Guidance Computer, or AGC as it is known, to full functionality. We even flew some landings with it, complete with the original Apollo 11 software running on it. In this iconic photo, the AGC is proudly presented with its Display Keyboard interface, or DSKY for short. The DSKY was how the astronauts communicated with the computer. It was sitting prominently at the center of the control panel, and was very heavily used during the missions. In fact, there were not one,
but two DSKYs in the command module, one on the main panel, and another one in the lower bay next to the telescope and sextant, called the Navigation DSKY. There was also one in the LM, the one that famously displayed the 1202 error during the Apollo 11 landing. You can can see it here, in-between Neil Armstrong and Buzz Aldrin during training. We admit to having had a long love affair with the DSKY. During our 2019 restoration, Carl built a gorgeous replica that we connected to our now functional guidance computer. It was quite
convincing, and we even reproduced the famous MIT picture, using our restored AGC and Carl’s DSKY. But Carl had to use one practical shortcut: he used LEDs in the display, a technology that was many years in the future at the time of Apollo. You see, NASA had developed a very unique and advanced solution for the DSKY: a solid state electroluminescent display, which we had only seen in some low quality footage. We always dreamed of seeing the real screen in person one day. We came a big step closer to our dream when friend and science genius Ben Krasnow made a replica screen for us, building electro-luminescent panels from scratch in his garage lab. He donated the screen to us after he was done,
and that gave us our first look at a real electro-luminescent display glow. But the story gets even better. A few years later, in 2021, friend and collector Marcel brought us a genuine Apollo DSKY display, that had been sold at auction. It was a real Apollo flight spare, that had waited in vain for man’s return to the Moon for the better of 50 years. Carl managed to reconstruct enough of the electronics to make it work, and lo and behold, it lit up perfectly. We were amazed by the result. Such a crisp, cold to the touch, high contrast screen. You’d think it was a iPhone screen in
1968.That was the closest thing to experiencing a real DSKY we thought we’d ever have. But imagine our surprise, when Marcel recently showed up in the lab one day, carrying a mysterious large case. Could it be?... [Marcel] A piece of Apollo history. You've seen various forms of it, but this the DSKY.
And, in the front... [Marc] It's a DSKY! [Marcel] ...oh my, there's an issue on this one! But that's okay we can fix that. [Mike] We have the technology. [Marc] Mike, this one was from MIT? [Mike] Yes, this is from an MIT simulator.
[Marc] And... oh, dang, it's in the shadow. Yes, thank you. It had a little accident.
[Marcel] So it was well used, especially some of the buttons here. You can tell what the entrance code probably was. And one thing we can get out of this is, since it is broken, you can see a little bit of the manufacturing aspects of how that display actually was created. Some of the contacts in there. [Marc] That's too bad if people break this kind of stuff. But I guess we have an extra screen for it.
[Marcel] I think we do! And, there was one thing on the back of this to note. Right here, there's a little dent. And it looks like it might have actually pierced the shell. So, I suspect the nitrogen might have leaked out.
But that's okay, we're gonna be probably opening this anyway. [Mike] Yeah. It's pretty easy to check, I think that's just like a regular Schraeder valve. [Marcel] Yeah. No pressure. [Marc] It's gone. [Marcel] Okay.
[Marc] And then we are stuck with another one of these connectors. Our nemesis! [Mike] Yep. Exact same connector. [Marc] The Deutsch high density connector. Well, I bought more pins, so...
[Mike] Yep. [Marcel] RAY 39, up on the bench. [Marc] Okay, well, pretty neat. [Mike] Definitely looks like some of the... like, the two and three were replaced at some point the key caps.
[Marcel] Yep. Yeah, I guess so we'll get to think, if we want to do full restoration, or just kind of examine it as is. I think we'll we'll probably do a display swap. And I'm hoping - we're not entirely sure - that all the proper guts inside here are there. That it's not just full of sand! [Mike] Very curious to see that. I've never actually seen the modules inside of DSKY before.
It will be interesting to see how many of the leaf springs on the keys are intact, and how many are not. Still has pretty good travel, this. There's one or two, I think that were a little sticky, but... This one's a little sticky. [Mike] Yeah, it's still clicking though. [Eric] We know where this is from, right? [Marc] That one might be broken.
[Eric] Looks like it was pretty heavily used. [Mike] Yeah. [Eric] All the letters rubbed off. [Mike] The documentation that I have for this one, says that it was sent to MIT for simulator use. So, didn't say exactly how much they used it and where, but... [Marc] Uh, MIT had only two simulators, right? They had the CM and LM simulator? Or did you have some other place where they had DSKYs? [Mike] I don't know. It's a good question. [Marc] Here is the best picture of the MIT Command Module simulator I could find. You can clearly see that the 2 and 3 keys are very damaged, and these
are the ones that appear to have been changed in our DSKY. Is this ours? It’s hard to tell, as I don’t see any other obvious details that match. Your guess is as good as ours. By the way, in case you are wondering, here are the main areas of the DSKY. On the left, there are a bunch of caution and warning lights. Which exact ones are on there vary from CM to LM, and did evolve with the development program. At the bottom is the keypad. The large buttons
with large throw were made so they could be operated safely with astronaut gloves on. On the right is the display area. The first number at the top right is the program you are currently running, program 63 in the LM would be the beginning of the landing burn for the LM, for example. When you do nothing you run program P00, lovingly called poo. Next are the verb and nouns, the directives you give to the program. Below that you’ll
find three lines of data, that you can read or use as entries. What numbers are displayed there depend on which Verb and Noun you are currently using. They could be very different things: roll, pitch and yaw angles, or altitude and speed, time remaining in your burn, etc... Even your 1202 error goes in there. It could even be an octal
memory address and a data value, as was needed for the infamous Apollo 14 hack. There are no legends of what is being displayed, no units, and no decimal points. You have to memorize all of that. But lucky you, there was a cheat sheet of verb and nouns, including values of the data lines, units and decimal points printed below the telescope optics to refresh your memory if needed. [Marc] So, do you want to keep it in its original vintage form, or do you want to make it work? [Marcel] What do you guys think? Should we fix it? [Mike] I want to fix it! [Marc] Stupid question for us! We fix everything, we can't stand it! [Marcel] All right, we're going to fix it.
And we're going to keep this display anyway, right? This might actually power up and light up, [Mike] Yeah, we'll have to check if it's shorted or not. If it's not shorted, then... [Marcel] Yeah. [Marc] And then you said, the display we have, the bezel is slightly different? We have to remove or add something? [Mike] So, yeah, this part of the displays is completely identical to the display that we have. But to provide additional protection for the screen, to stop stuff like that from
happening, they added an additional shield in front of it, in front of both of these. [Marc] Oh, we have the shield on the extra one? [Mike] So, as you can see, on this front cover, there isn't any room for the shield. [Marc] Yes. [Mike] So they milled out these windows a little bit bigger, and then added the shields. Which made the shields, but not the modules here, protrude a little bit from the front of the DSKY. [Marc] And, but just looking at the display, the shield looks to be removable.
[Mike] It is, yeah. You want to take off some E-clips. [Marc] So, maybe this happened, and they said: "oops, we might as well do a shield"! [Marcel] This could be the reason! [Marc] It looks suspiciously like what would happen to an iPhone, that doesn't have the extra glass protection. [Marcel] Oh, we can try bring it to one of those guys! (laughter) [Marc] Although this would have been great fun, we decided against bringing our DSKY to the Apple Genius guys for repair. We’ll take the repair matters into our own hands. [Mike] Oh, I saw some IDMs, or at least something in the shape of one. [Marcel] Ready? [Mike] Yeah.
[All] Wooooo.... [Mike] They're green! Look at that! [Eric] Indicator driver modules! [Marc] As we explained in the 2019 DSKY display episode, we expect the inside of the DSKY to have many relay modules. That’s because they did not have transistors that could switch the 250V AC necessary to power the electroluminescent segments, nor did they have ICs for memory. So, they decided to accomplish both functions using latching relays, which are relays with mechanical memory.
As we had shown in the previous episode, they used clever relay logic that requires only 5 relays per digit. That still results in lots and lots of relays. Each block II relay module, called an Indicator Driver Module or IDM, holds 22 relays. Counting the digits, signs, and warning lights, the DSKY needs a little bit over 120 relays, which should be 6 modules. And sure enough, this is mostly what we see here.
There is a problem though: one of the modules has a yellow dot, which means it has a defect of some kind. [Marcel] So, we can start on that. And then there's evidence of some scratching that was happening here, from previous attempts to get in here. So, I think we'll just kind of protect that with a little piece of cloth, or paper, or something. [Mike] All right, that's all the screws holding the two layers together? [Marcel] Take a look around.
So, we're tightening these to push it? [Mike] Uh, no, loosening. There's an E-clip there, that is holding the screw captive. But you only want to go a little bit, and then start turning the other one, to back it out evenly. [Marc] Aha, we have just encountered a jacking screw. These special screws are used to pull halves of assemblies apart when there is a connector joining the two, so there is no risk of tilting the pins. I had to machine a few of these NASA screws, when we rebuilt our main connector assembly for the AGC. That’s a screw that’s easy to damage,
if you don’t realize it’s a jacking screw, and try to force it out before the other regular screws are removed. Which is what had just happened here in the past, apparently. [Marcel] Ah, more scratches here. [Marc] Oh, we are not the first ones to open it up? [Marcel] Nope! I don't know how long ago...
[Mike] Oh, oh, oh! [Marcel] It did something. [Eric] Is the E-clip coming off? [Mike] You're losing your E-clip there. [Marcel] Oh, it's coming off! [Mike] Yeah. [Marcel] We need to be able to push it back down, I think. [Mike] Yeah. [Eric] So, there's just too much force on it, and it's pushing the E-clip out of the groove? [Marcel] It was already bent, from whenever it was last disassembled, I assume.
[Mike] Yeah. [Marcel] Someone probably ripped it out or something. [Mike] If you don't know that's there, you might just, like, "oh, I'll take out the screw"... [Eric] Oh, it pulled out too far? [Mike] Yeah. [Marcel] That would definitely do it. [Mike] Yeah, I have to imagine that this means that there's a bad relay on that one.
A yellow dot next to the part number means that the thing is non-flyable for some reason. But they had so many problems with the relays, well really throughout the program, not even just in the early ones. Apollo 12, um, twice I think, during the launch countdown, they had a relay short in the DSKY that just caused the EL panel to fully light up, and display all 8s. [Eric] Oh no! [Mike] Didn't recur throughout the flight, but it's like...
[Marcel] They had a little hammer their toolkit... [Eric] Bang on it with a glove... [Marcel] Percussive maintenance! [Mike] Yeah, maybe that's why they added the protective glass in front. [Marc] Okay, see, that might work. Now... (click noise) [Marcel] Oh! [Mike] Yeah. [Marcel] Looks good.
[Mike] Cool. [Marcel] Feels right? All right. Back in business! [Marc] Yeah, I see it taking this thing apart, yeah. [Marcel] It's holding? [Eric] Is it coming apart then? [Mike] Yeah, yeah, there we go. [Marcel] Just started to separate. [Marc] I'm done.
[Mike] All right? [Marcel] All right. [Eric] Lift off! [Marc] Ooh, aah, oh! [Eric] Wow! [Marc] And you have all the good stuff in your hand, right? So that's all the control. [Mike] Yep! [Marcel] Okay. [Marc] Looks in good shape to me. [Eric] Shielded connection.
[Mike] Mhm. [Eric] What's going on with that? [Marc] Uhuh, isn't it a bad cable? [Mike] No, that's... [Marcel] ...a repair. [Marc] It looks like a repair to me. I forget if it's this plate, or this plate, is like one of the only things we don't have a drawing of, mechanically in the DSKY. It's one of these two connector plates.
[Marcel] All pins are numbered, that's nice. [Mike] Mhm. [Marc] Which is that one? [Mike] This is the keyboard module. So,
this has the diode matrix that encodes the key presses into five bits. [Marc] Okay. [Marcel] So we put the back parts back together, we took all the front screws off, and now we'll see what's under here. [Eric] Wow! I like how each key has its own part number.
[Marc] Yeah, and you can see the hermetic little switches. [Marcel] Just look at it. [Eric] Wow, fancy plate! [Mike] Yeah, those front covers are very pretty. [Marc] Oh, hold on, hold on. There you go. Yeah, that's a nice one!
[Marcel] And we can also take this off, and put it in our test rig, and see what it does by itself! [Marc] I am just thinking aloud, if there's a short in that thing, and we... [Mike] We can test for a short before we put it on. [Marc] OK, yeah. [Eric] Oh! [Mike] Yeah, I see how that works. [Eric] Oh, my goodness! [Mike] Those are very expensive micro switches.
[Eric] Yeah, they look expensive. [Mike] Like $700 a piece on Digikey. [Eric] Are those the ones that are, like, welded, hermetically sealed? [Mike] Yeah. [Marcel] Ready? [Marc] Is it the same thing? [Marcel] 136... [Marc] Can you flip it on its other side, for the camera? [Eric] Looks like it's the same. [Marc] Oh my, it hurts just looking at it.
[Marcel] This one's definitely sticking. [Mike] We can fix that. If we undo these set screws, the whole shaft will pull up. [Marc] We have to do a little bit of surgery on this button.
So it's two-spring design. There's a big spring for large travel, and then at the end there's a little spring that goes and pushes the switch. So it goes easy, then hard. So, the key is stuck. But it's really this part. Okay. (Moments later...) [Marc] Okay, the new key is working? [Mike] Yeah, repaired zero key! [Marc] All right. We had to take it entirely apart, with springs flying all over. Okay.
So these are our three screens. A prototype one, a replacement one, and the broken one. And the simplest experiment would be to put the broken one on our setup back there, because it's all ready to go. And we checked that the there was no shorts, right? [Mike] Yep, there's no shorts. At least not to ground. [Marc] So, although it looks bad, it should be safe to put on the setup. See if it still lights up despite the break! We still had Carl’s setup from 2021, which we exhibited on occasion. So we simply plugged our broken screen into it, on the remote chance that it would somehow still light up.
[Marc] Man, if it still works, this is going to be a high reliability test here. Okay. High voltage! [Mike] Yeah! [Eric] Very faint. [Marc] Oh, there's some life! Oh, I have a 1202! Even in right next to the damage! [Mike] That's impressive! [Marc] Uh-oh, it's flickering in and out... You want to re-power the DSKY with that one? And then we have to make a contraption to drive the DSKY. [Mike] Right.
[Marc] So, it doesn't really matter which screen we have. [Eric] And we got to do something about that connector also. [Marc] Yeah, our favorite Deustch connector...
Well, congratulations Marcel, you have three DSKY displays. One with no cracks, one with a little crack, and one with a big crack! [Marcel] I speaks to the engineering that it works at all. [Marc] Yeah, amazing! It's like modern stuff. It's like the DSKY fell of somebody's pocket, and broke like a modern screen. So, not bad after its great fall! Anyhow, you know us, we’ll attempt to repair our poor banged up DSKY, and make it work like it used to, in the next episode. See you then!
2025-01-15 17:37
