We all know our cars are jam-packed full of little parts, things that connect moving things or bits that hold in fluids or spinning shafts or bits of metal designed to let electrons flow through them in controllable ways. We don’t always look at these parts for their aesthetic qualities, but sometimes you can’t help but notice. And today, for whatever reason, I noticed the strange visual appeal of a part that we generally don’t think of as visually all that interesting: the circuit boards of an ECU.
Specifically, I was looking at one of the first ECUs ever to be used in a production car, the Bosch D-Jetronic fuel injection system, which was really an update of the old 1950s-era Bendix Electrojector system. The first production car to use this system was the Volkswagen Type 3, and it was in an old brochure for the Type 3 that I saw this ECU board.
Here’s the picture from the brochure:
Let’s zoom and enhance on the circuit board, and what the hell, add a little blue tint:
What strikes me most about this circuit board compared to the more modern boards I see is the seeming chaos of it all. It’s of course designed rationally and to a very specific circuit diagram, but it just looks so haphazard compared to modern boards. There’s no true digital circuits on that ECU there, and about 25 transistors are doing most of the processing.
VW was quite proud of their computer-in-a-car and featured it in ads:
The “think” sign references the old IBM slogan, which was also “think.”
Here’s a period video with some great close-ups of the PCB and its components:
Here, look at a close up of a more modern ECU, this one from a Scion:
Of course, the components are far smaller and the density of the traces is vastly greater, but there’s also a much more rigorous grid-type organization system going on here. There’s orders of magnitudes more transistors and other components on here, now surface-mounted, and the whole thing looks like some kind of advanced alien metropolis seen from far above as opposed to the scattershot-looking complexity of the old board.
What I really like about printed circuit boards from the ’60s and ’70s though are the traces themselves, which often have a strange psychedelic-art kind of look. Here’s an example of what I mean from a very famous source, the now iconic Atari CX40 joystick:
See those strangely flowing and almost biomorphic shapes of the traces? That kind of thing was all over ’70s printed circuit boards, including some found in cars. Here’s the back of another Bosch Jetronic ECU board from the ’70s, with plenty of whimiscal-looking traces:
…or the snakey, labyrinthine goodness of this Mopar ECU from some Chrysler:
Anyway, next time you’re at a junkyard, I highly encourage you to look for something from the mid 70s or 80s, dig around and find some ECU box bolted under a seat or to a firewall and pry it open to get to the hidden beauty within. There’s so many more and better examples out there. They make fun wall art!
Sadly, recent trips to salvage yards revealed that few of them contain vehicles older an 20 years, and none past 30 years old.
“Cash for clunkers” took out so many good cars. My cynical self blames the auto mfgs. for this, reasons obvious.
I had helped someone work on a late Volkswagen type 3 and was blown away that it had electronic fuel injection. I didn’t realize it was the first mass produced car with it.
That circut board is obviously an overhead map that shows you the route to the gold that the Knights Templars passed down to the Freemason founding fathers. We just need to find the glasses that show us how to read the map.
Had a taillight circuit board fail in my 88’ Volvo. It had been melted by a previous owner using a wrong bulb that overheated. As I was on the road at the time it failed, I needed to improvise a temporary repair. I used tinfoil to bridge the melted area and dielectric grease to hold the foil in place and help conductivity. That was seven years ago; the temporary fix is still working fine.
pretty common fix on E38,E39 BMWs and their idiotic tail lights
“There’s no true digital circuits on that ECU there, and about 25 transistors are doing most of the processing.”
I think you meant to say there’s no integrated circuit(s). Transistors are digital devices, or at least used digitally. Heck you can even build a digital device out of tubes or relays.
Pneumatic (or fluid) logic devices also exist if you want to go one further.
Runs away screaming, analog computers, whhhaaaaaaaa. Nightmares from university.
Some carbs are pneumatic logic devices. Vacuum-operated secondaries for instance.
Used for digital devices is true, but transistors are decidedly analog devices. Even the ones inside a CPU.
My first car was a very used ’69 Variant, the second year that the EFI was installed. My friends named it Hitler’s Revenge due to its willingness to either stop running or sometimes just start dumping so much fuel into the engine that the oil overflowed, in a time before OBD was invented. Nobody, but nobody in Springfield MO would touch it except for the VW dealer – the only one in town and very well aware of that fact. Their solution to any and all problems was firing the parts cannon. IIRC the only one of the couple dozen possible failure points that didn’t fail at some time or another was the board. However, when it ran it was quick for the time and market segment, and the experience did kick start my diagnostic skills pretty early.
I too had a ‘69 Squareback (1990) with Jetronic. Got it from my dad for $500. It had a fresh top end, and ran on 3 cylinders until it warmed up a bit. Besides eating throwout bearings, it was pretty good (except in the rain, but you know, air cooled VW). It would get 37 mpg going up hwy 1 to SF.
The genius of the old circuit boards isn’t really appreciated until you look at what they replaced. Old point to point, hand soldered circuits and vacuum tube technology! No wonder VW was proud of what they had accomplished. I wish that every new electrical engineer would be required to refurbish an old tube radio or amplifier. For years, I ran a hobby/business repairing and rebuilding old tube amps for guitar players in the USA. I also restored hundreds of cool radios from the 1920 – 1955…especially tube radios for classic car guys. They make you appreciate the transistor, that’s for sure.
Yeah, my first thought was, “Oh, look, VW flattened point-to-point down to two dimensions!” Then again, if you look at old single-layer circuit boards from the 60s and earlier, they frequently have this sort of layout because of the lack of multiple layers constrains routing of traces and component placement.
I did crack open my D-Jet box on my 1970 Type III back in the day, but that was well before I started building / repairing tube gear as a hobby, so the novelty of the layout didn’t really register.
Funny, I could look at a single layer PCB and pretty well figure out what’s going on. Put the same stuff on a breadboard and I’ll be staring a very long time. LOL
I have an old S-38 Hallicrafters that needs to be recapped I think. Do you still do that?
My favourite feature of older PCBs is most of the components were through-hole soldered, with off the shelf components, making them significantly easier to repair for the home DIYer.
My ’86 S class has all the electronics functioning because any break in solder or failed component is easily fixed with TENS of dollars of components for a complete refresh.
Analog electronics with the PCB laid out by hand, using a handful of specialized drawing/drafting tools, look totally different from modern PCBs designed and optimized both for performance and ease of manufacturing with computer software.
At the time that Bosch board was created, the state of the art for PCB design was well on its way with maturing and taking into consideration the routing, length, and width of traces and the effects of inductance and capacitance on them — so sometimes the patterns visible are intentional to build a circuit that needs fewer, or at least less-costly, components like filters and inductors to work within spec. (Analog circuits can be highly susceptible to various electromagnetic effects, so keeping everything under control is a key design factor. A lot better than the point-to-point wiring days, where just putting ferrite chokes everywhere was a common solution!) Sticking precision electronics in a car of that era, with all the potential for ignition-related noise, was probably something that kept the engineers up at night. 🙂
And others just used wider traces where it was easier and cheaper to leave areas unmasked for etching and depositing the traces — especially where there were going to be a group of common connections. The layout of the board often said a lot about the design requirements that went into it.
You’re weirdly pretty….
grumble grumble circuit boards are cool. too bad that everywhere there’s design work or electronics work you can’t afford to live because everyone’s chasing the software dollar.
I remember looking at one from under the dash in my 70 Jeepster. The simplicity of it struck me.
What’s nice about that era of boards, and even the ones in my ’88 XJ6, are that they can often be worked on pretty easily. I have reflowed solder on the instrument cluster circuit board and in the taillight bulb failure modules to repair electrical issues. My son resurrected the ECU on his ’92 Civic in the same way, replacing a fried component and reflowing old joints.
Even though I can solder all the way down to a 603 surface mount component (resistors the size of a grain of rice) those old boards are just easier. I let my Jag specialist handle the greasy bits but I generally handle the electrical and accessory issues myself.
Don’t sell yourself short, an 0603 resistor is smaller than any grain of rice I’ve ever seen.
Visually I prefer the grid-style layouts, but I suspect the chaotic versions have shorter / more direct (i.e. more efficient) traces.
Working on such things *mumble* years ago I ruined a few neckties when they got snagged on the underside of PCBs. The through-hole mountings – as seen on the Jetronic board above – meant that every component had corresponding sharp bits of wire poking out the other side of the board.
Whenever I watch the printer destruction scene in Office Space, I hope Michael is punching SMT boards and not through-hole.
Thanks Torch!
My Grandpa had a VW Fastback with the FI and Auto Stik. He was in his early 70s and not a car guy by any means. It was difficult for him to “get” that there was no need to pump the gas before, and during starting of the engine.
Unlike the 61 Chevy Impala with a 409 and 4 speed that he had prior to the VW.
He was amazed to realize that his VW returned 25 mpg with an auto vs 8 mpg for the Chevy.
But then he was also born in 1902, so? He also broke his arm when he was 8 trying to crank an old Ford so he and best friend could joy ride around the Bronx.
Appreciate the good memories today.
Now I wanna open up our old NES (Nintendo Entertainment System) and see what kinda tomfoolery that circuit board might have!
I have four of the Type3 boards. One is in a running car and the other three are “spares” from parted out cars if the primary one dies. I’m still contemplating switching to a modern computer whenever I finish the resto on my ’68 Square.
That Type 3 ad…so, so good. The ‘think’ sign, the minimalist design, the copy–especially those last two sentences. Chef’s kiss.
I restore a lot of vintage radios, TV sets, stereos, record players and other electronics from the 1930’s- 1970’s. Prior to the 50’s all electronics were hand wired with point to point wiring, the undersides looking like a horror show with cobwebs of wiring. PC boards were drawn by hand for decades. These were then treated with a mask to make a pattern later to be used to mass produce the boards. The early boards were often terrible, made worse with the heat of vacuum tubes and their heat causing the board material to become brittle. The leads also will easily lift. By the time the car featured above came out most of those issues had been resolved.
Oh, the delightful Bosch analog EFI. My brother’s 914 had that, complete with the hunting idle issue. Probably a bad capacitor or something.
Manual-routed PCBs are definitely art, as was clean wire-wrap routing.
This was before we had software to help us design boards.
!This
three major changes from early ecus to modern:
analog to digital;
thru-hole to surface mount;
manual to computer-aided design.
(i can remember using black tape and an exacto knife to edit 20:1 analog pcb artwork…)
I like how circuit boards look like cities. It’s always fun to look at them.
And LOL at the fried Mopar ECU 😛
The difference: boards put together by humans vs. boards put together by robots.
Partly true. The surface mount components mean you don’t need a bunch of holes and globs of solder taking up space, plus computer aided design helps maximize use of real estate.
I recall debugging 17 – 28+ layer boards from the prototype shop by connecting them to the power supply and slowly ramping up the power until it worked or blew a hole in the board. Then connecting up the survivors to the testing harnesses and running them at progressive clocks until they proofed or failed.
Debugging and proofing chips was almost as much fun.
Certainly better than when I started making project boards in high school to plug into s100 bus systems, game consoles and early apples.
Ahhh the golden olden days.
IBM and ze Germans have quite a history that I’m certain Jason is well aware of. And the fact this thing is in a VW!
I must say, the Type 3 coupe is a pretty car.