Marco Reps - 2025-09-27
Get the best PCBs for your project at https://pcbway.com/g/Tj5om7 Oscilloscope current probes https://www.welectron.com/Strom More from me https://www.patreon.com/marcoreps Unsafe warnings https://www.etsy.com/shop/UnsafeWarnings Linearity test with unmodified DCC https://github.com/marcoreps/3458a/blob/main/linearity_test_3458B_guildline9930.ipynb Guildline 9930 docs https://drive.google.com/drive/folders/1yCkxmrz5F6rCXJvoFdVXGDckXsf4VkUX?usp=drive_link 00:00 Intro 02:35 First look 03:57 Small fixes 06:35 Secondary current? 08:48 Guildline docs 10:06 Works! 15:09 INL comparison 16:43 Teardown 18:41 DCC cores 22:55 More teardown 23:46 Constant current source 27:47 More teardown 28:58 Nanovolt amplifier #metrology #electronicengineering #pcbway
That constant current source is approaching alchemy levels of esotericism
Yup. They truly approach alchemy. When I was in graduate school we had a constant current source. It had vacuum tubes and took over an hour to warm up and also got more stable as time went on.
I still haven’t the foggiest idea how it worked.
Heated filaments in a vacuum lose electrons based on their temperature. A constant stream of electrons is a constant current.
You can literally scare away the ppms by yelling at it.
“I’ve never tested the linearity of the 1V scales on my 3458s” — 3458s plural, you know you’re on the Marco Reps channel 😂
We are reaching levels of esoteric metrology equipment previously though impossible.
That is no metrology. That is hardcore porn as it gets.
I can't decide which is more insane. That this thing was designed in the 1960s, that it apparently outperforms modern kit, or that you reverse engineered it to the extent that you did with no schematics. Amazing.
Guildline's excellent documentation was mentioned... sooooo
but yeah, crazy nice work
@DooMMasteR a distinction was drawn in the video between documentation and schematics
60's tech didn't use modern programmable logic, just straight up resistors, capacitors, potentiometer and so on with some IC's here and there. Even those were standards with lots of documentation.
It's way easier to retro-engineer than today's nonsense. And no, I am not saying it like it's bad, I am actually praising it. Discreet components make the whole design easier to maintain, replace and more durable than our modern use-and-throw-away logic.
A guy I knew in college (mid 70s) reverse engineered an NMR (nuclear magnetic resonance) instrument’s electronics. It was insane — through-hole passives, transistors, op amps and TTL circuitry, but an absurd number of components and insane level of complexity. He did it in exchange for keeping one of the two units available. (He was a biochemistry major but also wizard-level electronics nerd.)
@DaveEtchellsif he had to do it today, he wouldn't even get past the first Integrated Circuit (IC).
Not because of lack of knowledge or skills, rather because many copper tracks would probably go under/inside the board, becoming impossible to follow, many IC's wouldn't have datasheets (or badly explained ones), triple the amount of components, hard to do SMD solder, proprietary programed IC's and so on.
Complexity in the name of making things impossible to repair.
Holy... I typically can follow quite a bit, but this thing is 100% magic with unobtanium parts, beautifully combined in a gorgeous enclosure 😍
"craftsmanship and creativity we may never see again" very true, but I'm sure this thing costs as much as a couple houses did back then.
New fancy oscilloscopes can cost much more than regular house.
Probably not relevant but I found the device you've acquired mentioned in the CERN publication "The historical evolution of the DC Current Transformer (DCCT)" (CERN-OPEN-2024-006). Reciting from there: "A standards laboratory was started at CERN in the 1970s with Weston standard cells used to calibrate DACs and ADCs. A Kusters bridge with a 100 A range extender was obtained from Guildline, Canada, see figure 6. This served to calibrate standard resistors, shunts, burden resistors and complete DC-CTs."
@repsnew video spoiler?
In the collective move to ASICs and FPGAs, I can't help feeling some babies got thrown out with the bathwater. There was some seriously elegant analogue wizardry around just before the advent of the IC.
$$$ though...
Absolutely, but the math was nuts so the engineering was next level, not really practical anymore with the ease of modern devices.
@xxportalxx. Necessity really was the mother of invention, you're right.
I still feel like this about many things today.
@xxportalxx. what about the "math" behind FPGA? Code that often cannot practically be written by one man or even one team anymore.
I fixed one of these, just a bit more modern (70's). The whole thing was based around 741s and a simple royer oscillator for driving the 'magic doughnut'. The nanovolt amplifier was the craziest thing inside. The little peephole serves the purpose of adjusting the light pattern for photocells, because the servo has very limited range, so the idea is that the optical system have to be aligned to 0 (in terms of servo error) for it to reach peak performance when in negative feedback loop. It is crazy what people did with galvanometers baack in the 40s, 50s, 60s... I specialised in nuclear instrumentation. In the 40s and 50s they would just couple the ion chambers inside reactors to the lightbeam galvanometers inside control room, by glass or ceramic coax, and that was it. No logarithmic transimpedance amplifiers no nothing. By the end of 60s they started making amplifiers, but again - by using lightbeam galvanometers. And the logN/periode channels were just pure pipedreams. Like something you'd find in some mad alchemist (not mad scientist) lab. I mean differentiators powered by litteral pendulum clocks and precise capacitors... Things like that. 😂
Thats crazy talk!!
I want to learn more about that kind of stuff. Can you recommend books or anything in that direction?
Noooooo dont steal its heart!😢 It's such a cool bit of kit as is!
Great video!
Ohhh yeah a new marco reps video always makes me happy to see
This video brings back memories of 1972 when I first started work at the Government Aircraft Factory ( Aust ) Dc standard laboratory I use to use one of these bridges to test other ST voltage devices, and then again when employed at CSIRO Aust, Applied Physics Standards Laboratory, sadly by early 2000 it was replaced by a Datron dmm it also employed a saturated standard cell for its reference, and then the Fluke 8.5 dmm dominated all the measurements, Thank you for this video it brought me back to some of great work experiences I had with equipment and staff all great people. 😊
Woah a Datron DMM that I haven't heard of? With a saturated standard cell? Do you happen to remember the model number?
:)
Sorry @reps it has been a long time that I used the Datron model number, it would have been mid 70s
Datron Multimeter Type 1071
My colleague and I had Datron 1071s fitted with AC, Current and Resistance boards back in the 80s and 90s, supplemented with Solartron 7075s (later replaced with 7081s).
Seeing a piece of test gear like that developed here in Canada gives me a warm fuzzy feeling - which is good because it counteracts the PTSD I still have from 3rd year electromagnetic theory. Super excited to see the modifications to the eletrically-insesitve-but-mechanically-dodgy support infrastructure :)
I live 40 minutes from the factory. Hard to believe it's still in business in this day in age, but always great to see some Canadian designed and made equipment get some love 🇨🇦
The manufacturer sending over the docs? Absolutely magnificent! Shows that they actually still care about their products and probably hope that you can save it. And great publicity too!
Those people at Guildline are metrologists, which means persons who are crazy about measurement. And since there are so few of them in the world, they are happy when they find someone with the same interest. And they will gladly help that person to pursue that interest. It's like family. In the 1980's I worked with a model 9975, which uses the same CC principle to compare standard resistors. I was equally impressed by how accurate it is and equally stumped by the complexity of the machine.
I only have a surface understanding of what you're talking about but I'm happy that you're happy!
A thing of beauty and a joy for ever.
I have an old voltage standard they made that uses an ovenized zener mounted on a small board inside a Dewar flask. They helped me with the manual as well.
I've always wondered if using a dewar flask would be any good because I have a big pile brand new of dewar liners (just the glass vacuum envelope) I got from work and thought this might be woth a go.
7:46 it's obvious that they started the design of this machine, inexplicably, with an Enigma cryptography machine and then started making modifications. The routing of this signal can only be explained thus.
The funniest part about this is that as of right now, at least 29 people actually understood this joke based on what was shown at that time code.
This is pure madness. I can't imagine how this thing was ever conceived, manufactured, or used
something i never would have seen or even heard of without your video, and what a quality video it is!
It was particularly fascinating to learn @23:25 this instrument was built in Smiths Falls, which is only an hour drive away!
I love vintage analog tech
Thing of beauty
The old saying "They don't make them like they used to" is proven here yet again. Great breakdown!
The fascination starts if one sees the asset sticker "BUND PTB".
The wiring harness with the rotary switches reminds of a Enigma 🤨
Another sticker on the rear: Amt für Standardisierung, Meßwesen und Warenprüfung
Thanos is painting walls. Ceilings and floors too.
Saturday became a lityle bit better...Thanks.
This magnetic compensation method reminds me of a space-grade 3D fluxgate magnetometer with half a dozen Helmholtz coils and picoTesla resolution for satellite attitude determination.
It's like watching alien technology, from a species that went with slightly different paths on metrology evolution.
I am an electronics technician with about 25 years experience of repairing, designing and building any matter of electronic devices, but this thing is black magic for me.....I can get the principle, but listening to you explain it, it's like listening to a Chinese language channel. I am utterly amazed of the level of technology of the 1960's
I like to imagine that people from Guildline watch this video in awe of their forebears.
I want to nominate this for best video of 2025.
What a wonderful device
Someone put their all into designing and creating this and you have made a great informative and hilarious breakdown video for us to enjoy.
Thank you.
This brings back memories of Westinghouse magnetic amplifier modules made in 1964, that I then repaired in the 1990s. The cool thing was they had multiple inputs, and worked from 1 khz down to DC, so they could be used in servo loops to pull steel like taffy in a 6 stand rolling mill.
I could totally see doing something similar with modern hipersil toroids, microprocessors, and some relays.
1:40 "Numbers of transformer windings don't have temperature coefficients." They do if they get hot enough.
The way it just slid out was aesthetically pleasing👌
Rarely have such masses of futuristically sounding words been put together, as when one embarks on the journey of listing the components of this device. What a roller coaster, thanks for archiving!
I become more and more jealous of Marco's brain with every video. This is fantastic.
Absolutely S-tier video. I've got nothing more to say.
I like the idea of one of the most constant current sources ever :)
Wow - I have to watch this video again and have some serious reading of old literature to really understand how this fully works. Those magnetics gave me some idea's.
Very cool. Now it makes sense how the transformer can be used for nulling DC currents.
I started watching your videos for the cool electronics you take apart and repair but as a result of your enthusiasm I'm also developing an interest in the intricacies of metrology now!
Oh dear, there goes your savings and your soul.
Usually at least i can get the vibes of what you are doing and explaining but this one makes me question if I'm sentient and alive after all
Rep Rep
^^^If you “rep rep” it in the same cool synth voice I do in my head, you wouldn’t think I was so weird for posting this every video 👌🏼🥴 cheers
Almost every Reps does like this covers something I never even knew existed. This is so cool!
Absolutely mind boggling
Indeed... me too, always looking out for a new Marco Reps video. I love the dry German subtle humor.
Nazi sympathizer!
@WatchWesWork - 2025-09-28
31.87 minutes ago I thought I had a decent understanding of electricity...
@TD-er - 2025-09-28
This should have been the title of the video!
@andymouse - 2025-09-28
Yeah, glad I'm not th only one riddled with self doubt !
@uploadJ - 2025-09-28
... and metrology.
This was a very good find and documentary on the intricacies therein.
Thank you Marco.
@Zadster - 2025-09-28
Same, same... My M.Sc.(Eng) is looking at me and going... WTF?
@andymouse - 2025-09-28
@Zadster :)