All the PCBs in this episode have been donated by PCBWay. We thank them very much for that.
Same goes for Samtec, who provided connector samples and micro-coax cables.
Hello, and welcome
back. If you follow the channel, you know that we
are in the midst of restoring the Apollo communication electronics.
It started by us getting our hands on the S-Band transponder and amplifier thanks to
collector Steve Jurvetson, who later also got us the matching NASA ground test equipment.
The project scope extended further when team member Marcel got us most of the rest of the comms
system boxes, to the point that we now have a good portion of the electronics of the spacecraft.
And it keeps coming thanks to the generosity of our viewers: an anonymous collector
loaned us the missing ground S-Band transmitter that goes with our test set.
Plus for good measure, I recently acquired this missing piece at an auction. This is the CTE,
or central timing equipment, the clock and timing reference for the ship,
which also generates some of the reference frequencies for the communication system.
We are over a year into the project and are pretty far along, having resurrected the transponder,
and reverted our ground PM transmitter and ground PM receiver to their original Apollo frequencies.
In episode 13, we finally succeeded in getting a double locked PM link
between earth and the spacecraft on all original NASA equipment.
Quite recently, we got the FM downlink going, and were rewarded with TV from the Moon,
first in B&W in episode 21 and then in color in episode 22.
Lately we have been working on the PMP, or Pre Modulation Processor,
the central node of the spacecraft modulation and demodulation system. It is the central connection
point for just about everything, including most of the switches on the control panel.
So we are at the point where we have to start joining all the boxes that
form this very complex system, one that could simultaneously deal with ranging,
voice, data and television, all at the same time, and from lunar distances.
Which brings us to our nemesis: the connectors and wiring harnesses. Sometimes
we are lucky enough that we can find the right military connectors. It
then becomes a long task of figuring out the pinouts and making wire harnesses.
That’s how we did connect the transponder so far. But even then, we could not find one
of the Deutsch coax connectors that are used everywhere, so I had to improvise.
My newly acquired CTE is causing us double trouble:
it has a square connector that we can’t find any example of, and some more of
these Deutsch multi-coax connectors for which we can’t even find the contacts.
So in order to continue with our restoration, we need to make some connector adapters.
Let’s start with the CTE square connector adapter. We could not find detailed dimensions,
but measuring its pitch revealed something unusual, it was metric! We knew the Apollo
Guidance Computer did its guidance and navigation calculations in metric,
but we had not encountered metric mechanical dimensions yet. But thanks to that auspicious
choice, we have modern 2mm pitch Samtec connectors that will exactly match.
So Eric drew the short straw and started to work on the PCBs.
And right on cue, PCBWay just came up with new PCB colors. Nice! What about this gray at the top,
with a tinge of blue? Looks like that would go well with our Apollo box, don’t you think?
[Marc] So we are trying a new color.
[Eric] And we get a pen. And we got some boards. Oh!
[Marc] Matching gray color. Oh, they are gray!
[Eric] Look at that!
[Marc] Ooh, pretty. That will work!
[Mike] Nice!
[Marc] That will work. So that's supposed to go on the CTE. Let's go on the CTE, compare colors.
Yeah, that will be just perfect! We like it. I think those are Samtec's.
[Eric] They are .
[Marc] They are. Oh they are Samtec's, they are samples. Yeah, they're free Samtec stuff. Cool.
So Eric has wired his connector breakout, fantastic.
And we think we have found a pinout. You just have the 512 (kHz) hooked up? And then it's welded,
so there's nothing we can do about it. It either works or doesn't work.
So, I just turn it on, I guess? And we should have 512 kilohertz.
We do! Oh, it makes a noise. Frequency counter, all right. 512 kilohertz point zero zero.
[Mike] Nice!
[Ken] You got your money's worth.
[Marc] Yes!
I've done a little bit more wiring, and wired it into my BCD to seven segment decoder.
It's counting. Okay, let's do a second digit.
Oh, it's counting!
This is Apollo time.
[Eric] Let's see when it does the rollover.
[Marc] So the idea is to do that with a bank of Nixie tubes of course.
[Eric] Of course! 59... There we go!
[Marc] Okay, 60. I'm amazed at how close that is. It's just a quartz oscillator.
[Mike] Yeah, this is the less accurate backup clock.
[Marc] Right right right, that's the backup clock.
Normally it clocks on the AGC, which has a super duper clock.
All right, that worked a treat, and our CTE is counting, at least the seconds. We’ll test
it more completely in another episode. Eric then went on to the next design,
the Deutsch coax connectors. We have two versions,
the by 5 design like on the transponder, and the by 12 design found on the CTE.
[Marc] And, TubeTime has received a package!
[Eric] That's right!
[Marc] From PCBWay, our favorite supplier. But they are making new stuff.
It's a 3D printed offering, I think?
[Eric] They have a 3D print service. It's great, I actually used it the other day.
[Marc] Oh, you did? [Eric] I did!
[Marc] And then, so they can print transparent stuff, which is very transparent.
[Eric] I haven't tried the transparent yet,
but I have tried this, which is pretty tough. I think it's similar to nylon.
[Marc] Yeah, it's not your regular material at all.
Very nice! And then, they have the new colors. So, we have used the gray, because it goes well
with our equipment. And then, they have this pink. And these are vintage stuff, right?
[Eric] Yea, this would be great for a lot of vintage boards.
[Marc] I think this is imitating phenolic. And this, you'd think there is no mask on it,
but there is. It's just a transparent mask. So this is pretty cool.
And what did you get? Let's go to the stuff that you actually designed.
[Eric] All right, let's have a look. So what we've got here,
is a connector board that's designed to plug into these very special Deutsch connectors here.
[Marc] Which you couldn't find anywhere.
[Eric] Exactly. And so, we decided to just make them ourselves.
[Marc] Here you go, I have it. And if you flip it the other side?
[Eric] So here you can see we have the stencil for that.
[Marc] And I love the gray color. That turned out spectacular. Plus it's gray-blue,
which is actually the Apollo original color.
[Eric] Oh yeah it's just right.
[Marc] That's the prototype.
It's a pin in the middle, and I have the tube,
a brass tube that is just almost the correct diameter.
[Eric] It's very close.
[Marc] And then, we use some of the Samtec technology here. Samtec makes their own
micro-coax. Usually, you can't get the micro-coax just for yourself, but they bent the rules for us,
they made me a roll. And so, it's going to be much easier to put that many micro-coax,
rather than the regular coax. We won't have the mechanical problems. And that micro-coax
is incredibly good. They make some that goes to - I can't remember - 50 gigahertz or something like
that. It's crazy good. All right, so that's how we're going to make our new connectors.
[Marc] Oh, do we want to solder the pins first, the center pins?
[Eric] The pins go last
[Marc] Oh, you solder that from the other side?
[Eric] Yep.
[Marc] Oh, I see.
[Eric] A little bit of smoke. So that's the flux burning off. Oh, I see the solder melting.
[Marc] Okay, cool!
[Eric] See, they're starting to settle a little bit.
I can tug on this a little bit, it seems okay.
[Marc] Is it centered enough?
[Eric] Not quite, so I'm gonna go and reheat it, re-center it.
[Marc] And we just tried it and it worked perfectly. So if I do... Famous last words, "it worked perfectly"... Plonk! Done.
[Eric] Looks good! And it comes out?
[Marc] Clunk. Off. All right, we defeated the evil Deutsch connector.
And our center pins, they come from these old... I don't know what those are!
It's a type of IC connector.
And we're transforming into a connector factory. All right, we made a whole bunch.
Great, we now have working substitutes for the Deutsch coax connectors. But that is
small fry compared to Eric’s next task, which is a reproduction of the communications section of the
control panel. Not the whole thing fortunately, just this section right here at the bottom right.
[Marc] So, to test the PMP further, it's going to be difficult unless we wire it all
up. Eric here has gotten the short straw for doing a repro of the control panel.
[Eric] Uh, not the entire control panel fortunately,
but just this little section down here.
So that's got all the functions that go to the PMP and to the recorder, all those switches.
And in case you still wonder why we need this, it is because the wiring is complicated,
to say the least. Eric adapted the original NASA schematics and that yielded this. Which resulted
in a board like this. Actually, two boards, as the front one ends up being our front panel on which
the switches are mounted, complete with scale reduced 3D-printed reproductions of the knobs.
[Marc] Eric and Mike are giggling. Because, what do we got?
[Eric] We've got some boards!
[Marc] When a box from PCBWay shows up, we are always giddy.
[Eric] Oh my goodness. Oh, this is a big board.
[Marc] This is big!
[Eric] Look at this thing!
Oh, wow.
Wow, this looks really good.
[Marc] Actually, this one doesn't even have a
trace. They were all surprised by that. They went like, what?
[Eric] Yeah, no traces?
[Marc] Did you forget something? But that's just the front panel.
That's the back, with the electronics.
[Eric] So, then these will stack together like this.
[Marc] And, master, you've all the doo-dahs that goes with the thing?
[Eric] Yeah, I 3D printed some things to make it look
even better. Like this little 3D printed knob.
[Marc] Yeah!
[Eric] So we'll be able to rotate that.
And even the squelch knobs here. So this whole little mechanism will fit underneath.
[Marc] And you have the squelch wheel.
[Eric] And we'll get our little squelch wheels, like that.
[Marc] Excellent
So we have dual man operation here, for wiring the transponder.
I think Mike is on the military end, and Eric is on the IDC end.
Right, this is looking mostly finished, with the
round military connectors on this end. I think those two are PMP. And this is also PMP. So
we have some more to make. As you can tell it's not fully wired. But man, looks good!
The little squelch buttons. We can fantasize that we're rotating the antenna. The receive signal,
and then, three position switches.
Ready to fly pretty soon!