More Than Anyone Ever Wanted to Know About the ESB Helmet Interior Electronics

[Ord Mantell]

this is taken from my ESB build here, post 1 of 3

Research Project #2, Part 1: More Than Anyone Ever Wanted to Know About the ESB Helmet Interior Electronics​

I’m going to do a rundown of the parts for my vintage build of the electronics from the ESB helmet that I plan to put into my modified MCR G2 helmet, which is part of my ESB build. The starting point for this was based on intwenothor's work presented in his interior helmet build thread. I wouldn’t have attempted this or even known where to start without the information he provided there. He has my gratitude.

The more I looked at the parts he presented, the more intrigued I was by the challenge of 1) finding the correct vintage parts but also 2) being able to reconstruct the board so it actually works. Since I want to replicate the 1979 costume as much as possible, it’s desirable to have a functional replica of the electronics or at least explore if it’s possible. I'll also be building a non-functional second board for my SE helmet. I learned a lot along the way, including a shocking surprise about the ESB electronics board I’m not sure anyone in our community ever knew before. More on that later.

Just like with my last expedition into nerd town, my girth belt research project, I was starting at zero when I began this (and like that post, this one will probably only appeal to the die-hards). I knew next to nothing about electronics, but after months of research I now feel like I can fill in some of the gaps and make some corrections for some of the parts as previously explored by others. However, I’m admittedly an electronics newb so feel free to correct anything I got wrong.

Yes, this is a lot of effort for something that would hardly be noticed. Yes, there are excellent ready-made RF light kits already available. But let’s face it, if you have an Ever Ready flashlight in your gauntlet, or an accurate vintage chin cup, or an authentic MQ-1 calculator pcb or Honeywell microswitch in your helmet, you may already be on the path for doing this yourself — you just don’t know it yet. Especially after I conveniently serve up for you a short summary of hard-won research to find all the parts you need for it.

This project has two phases.

Phase 1: the parts. Identify and collect the needed components, including as many correct vintage ones as possible. This phase is complete for all intents and purposes and is detailed in this post.

Phase 2: the function. Put the board together so it actually works like the original—> powering the RF lights when the stalk is rotated to its horizontal position. Yes, there are concerns about vintage parts not soldering or working very well. I hope to share progress and results in a later post (part 2).

So pull up a chair, grab a giant bag of chips and a box of kleenex because this epic tome of is going to be one heck of a tear-jerker….

To begin, I understand that the electronics board in the PP3 helmet is virtually identical to the board in the ESB helmet. That board will be the basis of this build.

The first thing to note is the veroboard itself. It’s 10 strips across x 24 holes down and appears to be uncut, meaning maybe it was a stock size that was available at the time. I did a very long search and I couldn’t find a board like this. You can find 9 strips x 25 holes everywhere. It seems to be a standard small size board. So much so I counted and recounted the rows and columns on the original to make sure I wasn’t crazy. It’s definitely 10 tracks by 24 holes. Maybe it was cut after all, though most of the edges look too wide. Or maybe it came as part of a kit for a specific audio board type build. The jury is still out. (*update: RafalFett has discovered the source of this 10x24 board. posted here). I did check a Feb ’79 RS Components catalog I had access to and such a size was not available from them at that time. Perhaps one was in ’78. Until something better comes along, I opted for a board that was larger and cut it down.

The second thing to note about the veroboard is it’s not a perfboard. It’s a stripboard. Stripboard has copper strips on the back connecting all the holes of a single strip or track. When I started this, I didn’t know the difference. That’s the kind of electronics dummy I was. It does make a difference.

I found this image published elsewhere on the interwebs:

The unique patina suggests it’s not from the PP3 board. It’s probably the other one. The hero. But the point is this: if you look carefully you can see dark bands running lengthwise down the holes on the backside. Those are copper strips, verifying this is a stripboard.

I was able to get some vintage RS stripboard off ebay thanks to a kindly old man who was happy to dig through his pile of boxes full of old boards for me until we found some suitable ones I could use.

Note: the board must be cut so the strips run along the long axis, otherwise you won’t be able wire it correctly.

Let's break down all the parts on the board and look carefully at what each one is:​

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1. APEM Miniature p.c.b. ‘slide’ switch SPDT (RS stock no. 339-673)​

I tried learning some French but that didn’t help me track down a vintage version of this switch made in France by APEM. However, as intwenethor pointed out, this has changed very little over time and you can get a new one and just paint it blue. They are still made by APEM although the original company was bought out in the early 80’s. The new stock version is black and white plastic but otherwise almost identical to the late 70’s.

Right now I have a new stock APEM SPDT switch from RS components. I painted it blue with Floquil GN Big Sky Blue. SPDT stands for single pole double throw, which is basically a switch that can switch between two circuits. It can also be rigged as an on/off switch but that would seem redundant since the microswitch in the right ear serves as the on/off switch as far as I understand it. At this point I’m still assuming the SPDT switches between turning on the red LED’s in the top of the RF and the grain-of-wheat lights in the perspex of the RF. Please correct me if I’m misunderstanding the setup.


Here is the new stock slide switch before and after paint:

on my board:

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2. Silicon rectifier diode, 1N400X series, probably 1N4001 (RS stock no. 261-148)​

In the past this had been identified as a zener diode which are usually coded BZX or BZY, though a few are designated as 1N. The diode on the PP3 board is marked ‘IN’ (1N) which you can see under the silver stripe if you squint hard enough.

The ‘IN’ would be followed by a four digit number indicating the specific type of diode. From this picture there is no way to know what number series this actually belongs to, except by size and shape. But that still leaves dozens of possibilities. This is where a period catalog is useful. Consulting the February 1979 RS Components catalog I was able to find out what was available from RS at the time and gleefully eliminated most of the possibilities, assuming it was not too different than what was available the year prior. I’m now certain the diode is a rectifier diode from the 1N400X series not a zener.

As a start, I acquired some vintage RS 1N4001, 1N4004 and 1N4005 silicon diodes.

comparing the 1N4004 to the diode on the helmet board:

I can see a little bit of the final ‘4’ on the right edge of the 1N4004. Below, the 1N4001 vs the 1N4004:

The 1N4001 is the most common version of the 1N400x series and most versatile for lower voltage systems, but this photo still clarifies nothing. It could still be any of the 1N4000’s from 4001-4007.

Below, the 1N4001 and 1N4004 again, this time turned to show their double zeroes. Can you tell which is which? I can’t. Size and shape are identical. Only cosmetic difference is the final digit.

My current guess is the one on the helmet board is probably a 1N4001. I’ll have to test the board design with different values to verify.

These diodes were made in Taiwan, and still are, so they’re everywhere. You can get a bucketful for pennies. However if you want the vintage ‘RS’ branded ones (the ’S’ below the ’00' in the pic above is from the ‘RS’ brand marking), you have to search through electronics lots on ebay. I do have a few extra 01’s and 04’s left over and that goes for almost all the components in this rundown. PM me if you need something. If there’s interest I’ll put them up in the cargo hold.

on my board:

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3. Piher 0.5w high stability carbon film resistors 10Ω ±5% (RS stock no. 132-012)​

After a lot of looking around at resistors, I eventually learned that these particular resistors with their distinctive red/maroon base color were made in Spain by Piher.

From what I can tell Piher no longer manufactures these types of resistors. Newer stock is from Japan and has a cream base color instead of maroon, but old stock still seems plentiful.

Newer stock:

The striping on the resistors, brown/black/black/gold, indicate the total resistance is 10Ω with ± 5% tolerance. (You can verify any resistor rating with any number of convenient Resistor Calculators or find an app for your phone).

I’ve noticed the paint colors used for striping and marking resistors shifts a lot and is fairly inconsistent. Sometimes the gold tolerance stripe looks dark gold on these, sometimes nearly yellow — like the ones on the original board. Sometimes the brown looks nearly violet depending on the light. The placement and thickness of the stripes is also inconsistent, therefore finding exact cosmetic matches for what’s on the ESB board is a bit of a challenge. I found several vintage RS components packages of these on ebay, but they all had the darker gold stripe, and the stripes are a wee bit different thickness than the versions on the helmet board. I was eventually able to get a handful of good matches directly from a reseller in Europe, however an easy repaint of the gold stripe could make the others match pretty well, too.




Stripe thickness, spacing and color are not entirely consistent from batch to batch or even within the same batch:

on my board:

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4. RS branded 7416 integrated circuit, hex inverting buffers (RS stock no. 306-364)​

Seems everything we need to know is written on the top for us. It’s still possible to find vintage IC’s with RS branding but the logo's appearance changes from different time periods adding to the challenge.

Different styles of RS IC branding over time and across IC types:

The very large over-sized logo with the square outline seems less common. I’ve found some with matching logo stamp but so far not a 7416. For the time being I chose a vintage Texas Instruments SN7416N as a functional stand-in because it’s physical appearance is exactly the same with the left notch and right circle dimple. It was also made in England like the RS branded one. I did get a 7472 and a 74107 both with the same over-sized logo style as the 7416 on the original board which will do fine for a non-functioning board:

I can put stickers on any of these to match the correct appearance more completely.

Note: as pointed out by intwenethor, both IC’s on the board are mounted on IC sockets. The vintage stock is pretty much indistinguishable from the new stuff you can find for pennies. You need 14-pin.

 

[Ord Mantell]

continued, post 2 of 3

5. National Semiconductor DM7400N integrated circuit (RS stock no. 305-490)​

The wavy ’N’ logo is the logo of National Semiconductor (1959-2011). I think Fairchild Semiconductor did make some of the earliest ones after they were invented at Texas Instruments, but IC’s made by Fairchild have their ‘F’ logo as in the pic below:

History side note: IC designer and crazy genius Bob Widlar left Fairchild in 1965 for National Semiconductor and made it into an IC superpower.





You can find vintage National Semiconductor 7400N’s on ebay without much difficulty. The appearance of the NS logo changed over time. The newer ones, mid 80’s and beyond, have a stripe on the left with a small wavy N. The older ones have an ’NS’ in a funky computer font which was in use as late as 1976. The era of 1977 to 1982 is the style we see on the original board.

Different logos and fonts for National Semiconductor over time:

The logo style as seen on the board is not hard to find. Finding 7400N’s with the 027P designation is a different story. That’s a lot harder. I’ll explain why in a moment.

After a very long tedious daily search, I did find DM7420N’s on ebay with the exact logo and font size as well as the 027P designation. The 7420N doesn’t work the same as the 7400N, but I bought some anyway just because the stamping looks so much like what’s on the helmet board. After such a long search, it was a thing of beauty to behold.

The closest I could get with a 7400N was a 007 batch code, which isn't too shabby. No sticker necessary really.

License to kill? Yes. Deadly. See below.


A Bitter Truth Revealed

Just when I thought I had become powerful with the force and had this part in the bag… after all that hunting and researching, I may have finally dug a little too deep. Because it turns out there is a bit of surprising news about that “027P” designation. I was curious about that code, so I looked into it… I wish I hadn’t. There is indeed bliss in ignorance, as they say.

and so comes the plot twist nobody saw coming…

It turns out ‘027P' holds some important information. It's a date code in the format YWW (YearWeekWeek) for the manufacturing date, which tells us when the IC was made (‘P’ is the plant ID). Each week had its own code, so this is why finding a specific code is tough. It has to be a chip made the same week at the same plant to have the same code. National used only the last digit of the calendar year until 1983 when they switched to a YYWW format. So for example, an IC with the code 837 would read ‘8’ as the year 1978, and 37 as the week of the year, so it would mean the IC was manufactured in 1978 week 37. It’s not an expiration date. IC’s don’t expire exactly (more on that here). It’s a manufacturing date. Full explanation here on how to read National Semiconductor date codes (probably from the early 2000’s).

another example: this National Semiconductor MM5782N has date code 620, which is 1976 week 20





So our ‘027P’ batch code means it was manufactured the 27th week of year 0. Well, what’s year 0? The 0 stands for 1980.

We know the ‘0’ is 1980 not 1970 because the logo style confirms the era as post-1976 and pre-1983. I hear the gears grinding in your head right now. That’s right. This IC was manufactured and put on the board well after ESB had already hit theaters (ESB release date was May 21, 1980). I truly did not want to believe this. It had to be some kind of glitch. This could not be how to read the batch number.

For a couple of days I continued to believe that's not true, that's impossible. But the more I looked into it, the more the evidence piled up confirming ‘027P’ did, in fact, mean it was made in mid 1980. The week of June 30 to be precise. There’s just no way around it: this chip was not on the board during the filming of ESB. How can this be? Why didn’t Ben tell us? I don’t know for sure but I have some ideas.

First, it sits in a socket, so it’s actually very easily removed and replaced. No soldering or rewiring is required. Second, perhaps there was a problem with the original IC so they changed and/or updated it. But why would they update it after filming? The only answer I can conceive of is it was done to prep for ROTJ when they still thought they would use the ESB helmet for Episode VI (new pet theory: maybe the guy who put in the 027P IC was the guy who dropped the helmet and gave it the giant left eye crack!).

So for this build, the 1979 filming helmet, the exact make for this part is actually unknown and may be lost to time. $#*%@! The original IC would’ve had a different batch code, different font size, too, or could’ve even been different make altogether. All I can do now is guess. And my guess is it’s either a RS-branded, National, or Texas Instruments 7400 from late ’77 or early ‘78. We know the ST had working electronics installed prior to June 28, 1978, so those are the most likely 7400 IC’s to be on the board by that time. I do have a Nov 1977 NS I can use unless I find an RS branded one, which might be the more likely chip.

But wait. There’s yet another plot twist (this is where you might need that box of kleenex). Remember the RS 7416 (#4 on our list here) which endeared us with its oversized logo and home-grown British charm? It has the same wretched secret hiding in plain site. It’s our own character flaw not to see through the deception sooner. It’s batch marked “8105S.”

That’s a YYWW date code. I’ll give you three guesses what that means. That’s right. Another surprise betrayal. That one was made the week of Jan 26 1981!

Monkey spit! How can I make a faithful duplicate of the 1979 board if the two main components were swapped after filming, leaving no record of what they were? I don’t know. Maybe the search for the exact IC’s was for naught. A complete waste of time. Thanks National Semiconductor… you and your namby-pamby date codes.

Real ad for National Semiconductor. Clearly the villain:

One thing we must consider in light of this information: there is a possibility, however unlikely, this entire board was fabricated after ESB was released. It’s possible the original one which was used for ST and the ESB hero during filming was discarded and replaced by this one.

(last animated gif, promise)

There are, as yet, no other components on the board I can ID as being strictly post-1979 in origin, so let’s just banish the thought. The consequences are too terrible to contemplate. And it's pretty unlikely. > (*update: this may actually be the case after all: evidence here. summary: the actual stripboard itself looks to be dated mid-1981. All the date codes found on the board here)

Whatever the case, there is certainly a mystery here. An untold story. I think it lends solid evidence that the ESB hero was originally intended to be used for ROTJ early on. The damage to the helmet is probably why they changed course. And now we can probably pin down the timeline of the damage to after the IC swap but before the ROTJ stunt helmets were made. Which would put the date of the damage no earlier than Feb 1981, but probably some weeks later than that at minimum since it has to go from the plant to the warehouse and be added to stock before purchase and delivery. I don’t think we have a date yet for when the stunts were made.

Ultimately, the true tale of the IC switcheroo will have to be for another time, by someone who knows what happened. Probably that guy who dropped the helmet.

I understand there might be those who don’t want to accept this conclusion. I don’t blame you. I prefer delusions to reality, too, in some cases.

Caveat: I acknowledge that the interpretation of old date codes rests on assumptions that are hard to verify beyond doubt, namely that the codes present on these specific chips are in fact the common YWW and YYWW formats. There are other formats and some plants simply did the formatting wrong from time to time. To clarify this mystery will require some solid evidence. One possible place this could be found is on period data sheets from RS Components and National Semiconductor for these series chips. They *should* mention the dating convention used for the product at that time. The earliest data sheets I've been able to find so far are 1989 for National and nothing for RS. I'm more than happy if we can find information that proves I got it wrong.

I did reach out to someone who is very knowledgeable on date codes just to see if I am totally off-base with my interpretation. I will see if he will let me mention him or if he wants to join the discussion, but here is what he had to say regarding the mystery:

Personally it seems unlikely that those are the original chips, as the date codes look to be completely straightforward, and indeed newer than the film. (Good film, too! My least favourite as a kid, and then my favourite as I got older.)

Seems like a pretty smart guy if you ask me. He certainly understands ESB's proper place in the Star Wars saga (as an adult at least). For now, I suppose staying with a period correct 7416 and 7400 will do since no one can ever know if it’s accurate or not, which is a reality that stings after so much research. Or there is the possibility the 7416 could’ve originally been a 7406 before it was replaced, since that’s nearly the same. If anyone wants to make the post-ESB board as pictured, there’s no shame in it. I guess. Heck, I’ll probably make one for my SE helmet. If anyone wants a 7420N 027P from mid 19freakin80, just PM me. I have a few. I’ll be glad to get rid of the stinkin’ rotten backstabbing wretches.

on my boards:
The June/July 1980 chip, post-ESB (for a non-functional SE board)

A November 1977 that could've been on the board by June 1978 (for the functioning 1979 hero helmet)

6. Unknown make tantalum bead capacitor of unknown specs, ??µF / 6.3 volts (RS stock no. 102-730?)​

As if the treachery of the IC’s wasn’t enough, there is no time to recover before we must now come up against an actual unknown. These blue tantalum capacitors were the one component I have still not been able to ID a maker for. If anybody has ideas, please speak up. I suspect they are from West Germany (anybody remember that country?), but that’s just a hunch based on the use of the comma instead of the period on the ‘6,3v’ on component #7 below.

It’s hard to know the exact specs just by the top-down outline, so we are left to guess yet again. But let’s make an educated guess based on what we know from #7 on the list below. The working voltage is probably the same, 6.3v, since the battery pack is 6 volts. But it looks beefier so the capacitance is probably higher. Exactly what, I don’t know yet, but it’s definitely higher than 47uF. Maybe double. A 100uF, if that’s it (just a guess), is stock no.102-730. I’ll have to wait until I test the design in phase 2 to see what works, unless someone with knowledge of the original part wants to let us in on the secret.

When sourcing vintage parts like these sometimes you just have to go for broke and buy giant piles of the stuff to find what you’re looking for. Most of the time sellers won’t pick through them for you. They’re lazy. Ah, you already know this. Ebay 101 stuff. You got it.

If anybody wants to do a non-functioning cosmetic board, there’s plenty of stand-ins in this lot from Germany that’ll play the role of part #6 and #7. PM me if interested. I don’t think I will ever run out.

on my board:

7. Unknown make tantalum bead capacitor 47µF / 6.3 volts (RS stock no. 101-844)​

Finally. An honest character. No guessing needed here. It’s really tough to find these exact values in blue bead capacitors like this. Like I mentioned with the previous one, I suspect these were probably made in West Germany, so you might want to brush up on your Deutsch and search ebay DE (tantal, perle, kondensator, elektrolytkondensatoren, elko), although on rare occasions you will see RS packaged tantalums pop up in the usual spots on ebay though I’ve not yet seen blue ones. Word on the street is these old blue capacitors are trouble, especially in the low voltage range such as this. They’re unreliable and like to go out in a blaze of glory. Sounds like potentially good times. This will warrant further discussion in part 2 (here’s an informative paper on the broader problem of all tantalum capacitors here). Remember kids, always wear your bonnet!

If the blues give me trouble, I have new stock yellows ready to fill in.

on my board:

8. Neohm 0.5w thick film resistors 3.3kΩ ±2% (RS stock no. 145-311)​

And as we come to the final component on the board, we enter the land of the unicorns. At first glance these look like normal 1/4w 3.3k ohms (aka 3300, or 3k3) molded carbon film resistors made by Allen-Bradley or similar. But look closely at those stripes. The fourth stripe (from left) is red… and that’s what makes this a unicorn. That’s the mark of ±2% tolerance. It turns out RS components didn’t have carbon film at 2% at the time. Only 5% tolerance was available (RS stock no. 131-312). It also turns out 2% carbon resistors were not common in the UK at all in this period. The ’79 catalog did have metal oxide resistors at 2% (pic below). They were 1/2w and the dog-bone shape with blue/gray body color. Possibly made by Electrosil. But obviously those aren’t the ones.

Vintage RS Components 2% metal oxide had a blue/gray body color:

But RS did have another 2% resistor at the time: 1/2w thick film resistors. They are the right size at 6.5x2.4mm and the right shape with a molded case, and look the part. They were made in Italy by Neohm (oh boy, many, many Bothans died to bring us this last piece of information).

The reason I say we are in the land of unicorns is because well, the obvious: they’re really tough to find. After searching long and hard it became clear that finding a pair of these was not going to be easy. In fact, I was preparing alternatives because it began looking highly unlikely that I would ever find any before my children left for college (they’re in 2nd grade currently).

Unicorn sightings in Bath

But then… the clouds parted to let the light of the Force shine upon my sad little 1979 vintage replica board, its heart ripped out by IC date coding practices, etc. I came across an auction of old electronics parts in three large cabinets in Bath, England. In a couple of pictures, random bins were slid open to show their contents. One of the few open bins happened to be 3.3k resistors, and in the jumble of different makes and power ratings were four, possibly five thick films with the glorious fourth red stripe. What?! I immediately copied the photo and blew it up super large so my bloodshot eyes could see clearly through my tears of joy. I sat in stunned silence for, I like to say 30 seconds before I sent the picture to a friend to get a second opinion. Was I seeing things? It didn’t even matter. I was going to bid no matter what. And bid I did, using my ‘secret’ Star Wars number, a random number that comes up more than once in the OT. And won the entire lot. For five tiny resistors.

And it got better. What I thought was four, maybe five of them, turned out to be seven. Then I got lucky again — the seller was very pleasant and kind and sent me just the unicorns, charged me only a small amount for them and put the rest of the lot back up on ebay.

And that’s how easy it is to find these suckers. No sweat.

Let’s play ‘Spot the Unicorn.’ Can you find the 3.3k ±2% resistors in this lot?

Look closer

ah yes, there they are.

On the other hand, 3.3k carbon composite/film resistors at ±5% and ±10% are plentiful. Several manufacturers made molded carbon resistors with this same look, Allen-Bradley, Stackpole, Morganite, Ohmite, Vitrohm, TRW, Arcol, and on and on, and yes, even Neohm made these, too. I spent a long time down this rabbit hole before discovering the thick film resistors. If the 2% Neohm thick film is a unicorn, then these 5 and 10% carbons are horses. They’re ubiquitous and look the same except for one small but critical detail — the final red stripe.

Fourth stripe in gold means 5% tolerance, silver is 10%

The last two pics are carbon resistors made by Neohm for RS. You can see how similar they are to the thick film resistors on the original board. I want to emphasize these carbon types because they’re so cheap and easy to get, therefore they make an excellent replacement for a non-functioning cosmetic board. It’s what I’d choose for a SE helmet since the SE almost certainly didn’t have working electronics. The 1/4w would be the size you want. Just paint the fourth stripe red and you’re set. They won’t work electrically since their power rating is half of what’s required. The 1/2w carbons are an option on a functioning board, but will take up more space so wiring them in will require a modification of what would have been done on the original.

Neohm 1/2w 3.3k ±5% carbon film resistors:

They should work electrically the same as thick film resistors, assuming the 2% tolerance is not really necessary. But if it is, there are other options. There are new stock 2% metal film resistors that can be used and repainted that should work just fine, or Caltronics made 2% 3.3k 1/2w carbon film resistors — but they are the dog bone type.

For now, my fingers are crossed the unicorns I acquired will do what they were meant to do. I tested them and they were all performing rock solid at 1% or less which is perfect.

on my board:

At last, we are at the end of the journey and I have my happy ending. I ride off into the sunset on my unicorn(s).
[music swells to an emotional climax]

And thankfully that’s it for the components on the board. Here’s an easy shopping list for those of you who made it through all that. Congrats. If you skipped right over and came straight to this, you’re cheating. You should really take a moment to consider your lack of moral character:

1. Miniature p.c.b. ‘slide’ switch SPDT, made in France by APEM (RS stock no. 339-673)
2. Silicon rectifier diode, 1N400X series, probably 1N4001 (RS stock no. 261-148)
3. Piher 0.5w high stability carbon film resistors 10Ω ±5% (RS stock no. 132-012)
4. RS branded 7416 integrated circuit, dated 1981 (RS stock no. 306-364)
5. National Semiconductor DM7400N integrated circuit, dated 1980 (RS stock no. 305-490)
6. Tantalum bead capacitor of unknown specs, ??µF / 6.3 volts (maybe RS stock no. 102-730?)
7. Tantalum bead capacitor 47µF / 6.3 volts (RS stock no. 101-844)
8. Neohm 0.5w thick film resistors 3.3kΩ ±2% (RS stock no. 145-311)








The RS stock numbers listed are vintage and some are discontinued.

 

[Ord Mantell]

continued, post 3 of 3

But that’s not all! That’s just the board. We still have the rest of the kit to worry about to get the lights up and running properly.


> RS 4AA Battery holder, long. I was able to find a vintage RS Components battery holder, almost but not quite the same as in the helmet. It’s labeled RS stock no. 488-163 and is marked “UM-3x4 6V” molded into the plastic along the spine.

This holder was probably made in Japan or Taiwan. I think Japan is the only country which labels AA batteries as UM3 but battery holders made in Taiwan also use that designation. The spine on the vintage are wider than current versions, more like 1/2” wide as opposed to 1/4”, and smaller protrusions for keeping the battery in place. I passed on the vintage holder since it wasn’t the exact same model therefore not worth the beefy price of the giant lot it was in. I’ll stick with the cheap one from amazon for the time being.


> Two Mulbrod wire clips made in Germany. Luckily I was able to get some. Currently there aren’t many sources for these. Grab ‘em if you find any.

> Rainbow wire 20AWG (orange/red/brown/black) (this was my source)

> One vinyl 9v battery snap. I got vintage because the vinyl is shaped nicer and more like the one in the helmet as opposed to the cheap misshapen stuff you get from most suppliers today.

> The well-known Honeywell micro-switch 1SX1-T preferably with 77 or 78 manufacture date (I believe that’s a YYWW code again, so preferably nothing after 78-20 or so if you want to be hyper accurate. Mine is 78-41, a little past that date! Drats! Well, maybe the ESB had a slightly newer one than the ST helmet. Let’s pretend for now).

> Two red 5mm rounded LEDs. No reason to get vintage for this.

> Three 2mm 6v grain-of-wheat lights. terminal fettler ’s beautifully done RF top has the correct size holes for these.

I’m choosing NOT to put vintage batteries into the functional version. Should you put replica vintage labels on your batteries? Don’t be ridiculous. Of course, you should.

With all the parts collected, I’ve temporarily put them in place and plan to solder the connections properly after testing the design with prototyping software.

But thanks to the left turn at Albuquerque along the way, I’ll be doing two slightly different builds for the board. One for the ’79 ESB hero helmet, dubbed ‘theoretical’, and one for the SE, dubbed ‘post-ESB’ which is what we started out building without knowing it. The '79 board I will be making functional, the post-ESB I will not bother to wire up because the setup was trashed by the time the SE filmed. I'll put a sticker on the RS chip on that board, though, to turn it into the 7416 until I can find a real one of the correct period.

Part 2 will cover the work to make the theoretical 1979 board functional (now under way).

 

[RafalFett]

Here's my post from that thread:


What a great post, Eric! More exactly 3 posts!

A couple of years ago I tried my luck with the board, bot never got as deep as Eric did. I found the same miniature PCB slide switch and did some research regarding the color codes of the resistors and diodes:

At the same time I tried to decipher the writing on the Pre-Pro #3 board:

And I got these variants:
ORDER CODE 200 - 21076C WR20781 or WR20/81 or WK20781 or WK20/81
PART NO.

Thanks to Eric's thorough research, I tried my luck for the Veroboard using the writing from the PP3 board. I got some promising results in old magazines, which automatically led to hours of browsing. In this magazine from November 1979 (attached to the end of the post) at page 30 I found an ad:

Do you see it? It's in the center of the page:

And the code from the PP3 board writing 21076C with the accurate size 2.5"x1" (or 63,5x25,4mm) and 0.1" (or 2,5mm) pitch. The pitch is the distance between the holes, which was/is a standard for electronic components. Also there are some interesting projects with the 10x24 holes Veroboard, but the most interesting is on page 25: a LED flasher.

And a Veroboard advertisement found in another magazine:

And a bit of explanation of the board types found in another magazine from October 1980 (at page 33):

Regarding the date codes on the ICs, I think this is still debatable, because there are/were lot of codes between companies and even between periods. Here are some articles I found while searching ==> Date Codes and ==> IC date codes – Telcontar.net.

This explanation might be a good example:

However, there are also particular occurrences of ICs where such a code is present that is not a date, or not a relevant date. In many cases, these codes can be readily ruled out. For example, the National Semiconductor INS8048 chip above has the sequences “0810” (suggesting 2008) and “8048” (suggesting 1980), which can be discounted on the basis that an Apple Keyboard II could not have been made around either of those dates. Further, “8048” and “8049” indicate models within Intel’s MCS-48 microcontroller family, widely used as keyboard controllers. MCS-48 models were second-sourced to a variety of companies including National Semiconductor (the INS8048 pictured above) and Signetics (the SCN8049H pictured above), so those numbers will appear on many keyboard controllers.

But as Eric already discussed with the guy from Telcontar, it is highly possible that the IC's were replaced after ESB and before ROTJ.

 

[Ord Mantell]

Just to add some corroborating evidence for the YWW dating codes for National Semiconductor during the late 70's, below is an old 69SD5 from a data entry terminal for a Burroughs TD-730. These were made in the late 70's.

The board itself has the date code "7834" which is 1978 week 34. So we can expect that dates for the components on the board would be tightly linked to the same time period. And indeed there is an National Semi chip on this board, the gold one on top.

the date code of the board, 7834:

The NS chip with date code 826:

The only way to read the date code of the NS chip so that it is the correct time period for the making of this board is YWW, thus 1978 week 26.

Again, what I think this means is that the chips on the ESB helmet board were swapped out well after ESB was released, probably in the summer of 1981.

 

[Mandokarla]

I don't have the finer understanding of electronics to understand half of what you are telling me in this write up. But the amount of effort you put into this is amazing and I had to say well done.

 

[RafalFett]

Just to add to the "date code" flame, yesterday I was searching for more info regarding the Veroboard using the 21076C order code. As usual, I found lots of adds in magazines from late 70s to early 80s (this period is what really interests us); here are 2 pages from Electronics Today International from November and December of 1979:

(the add is in the center of the page)

(the add is at the bottom center of the page)

So far, so good... But look at the order codes:

Remember the code taken from the Pre-Pro #3 circuit board? Here it is again:

ORDER CODE 200 - 21076C WK20/81

PART NO.

The add from November says VERO 21076C while the one from December 1979 says 200-21076C. See the problem? The problem with the date the code was changed? End of 1979! Also on that code from the circuit board we have this: WK20/81. Does this means Week 20 (May) of 1981?

 

[Ord Mantell]

Wow. Thanks RafalFett. Amazing catch. This is possibly very bad news, indeed.

The only hope for a counter argument is that the code was always 200-21076C and the 200 was simply left off in the earlier ad for space requirements, while at the same time, the numbers at the end of the board would need to be something more like WR20781 and do not have anything to do with a date. But that's a lot to ask for I think when you put all the pieces together like you just did.

If that is a date code on the board then the case for the whole thing being made in 1981 is almost beyond dispute. The chips are July 1980 and Jan 1981 so that would line up very well with a June 1981 board.

Wow, yes, I feel just like Grogu there. Holy moly. Perfect gif for this. lol

 

[RafalFett]

Judging by this image of the PP3 board, I don't see the the top horizontal line for the number 7, so this is definitely a /:

The only logical explanation I see now is that the ICs on the board were burned out and possibly damaged the circuit board too, so the board and the IC's (and possibly some other parts) were replaced for ROTJ.

 

[Ord Mantell]

Just to summarize so everyone can easily follow what's being said here.... The evidence is piling up the electronics boards in the PP3 and ESB were made after ESB filmed:

 

[RafalFett]

I would use the word re-made or parts replaced. It is written in the Progress Report sheet that Bob (or Rob) Dickinson was working on the electronics for the helmets, jetpacks, gauntlets and chest displays:

 

[Ord Mantell]

Whatever the terminology, the meaning of it is this: that board was not the one in the helmet for the movie. The original board is gone. Did it have the same design? Probably, but for the moment we have no idea what the original 'filming' board actually looked like.

 

[RafalFett]

That's correct. Until we have a detailed photo of the inside of the helmet during ESB, we will use the post ESB setup.

 

[Ord Mantell]

My preference will be the theoretical 1979 board for now. It can't be more wrong than the post ESB setup, though I'll probably change the 7406 back to a 7416 dated late '77 or early '78 if I can find one. Those suckers are hard to come by. But the 7406 has the same logic as I understand it.

 

[RafalFett]

It looks great! Will you paint the order code on the board?

 

[Ord Mantell]

I'm going to give it a shot! I've got better board on the way, so will have to wait.

 

[RafalFett]

Just did a vectorized version of the rangefinder electronics to scale (it should print fine at 100% scale), but can be also imported in any good graphics program to separate the parts you need: