Oscilloclock.com

Handcrafted Scope Clocks with circle graphics

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  • Z Core makes Blanking easy!

    Z Core makes Blanking easy!

    Here at the Oscilloclock lab there’s nothing more pleasurable than helping put a cherished vintage oscilloscope back into action. A new lease on life!

    That’s why when [Chris] reached out about his early 1970’s Conar 255 oscilloscope, wanting to convert it into a Vectrex gaming machine, we were naturally excited!

    The Conar 255 – “space age technology” per NRI Journal Nov/Dec 1973
    Beautiful vector graphics! Image by When Chemists Attack

    The original Vectrex was an incredibly cool device. Instead of the pixelated, blocky graphics of the time (anyone remember Pac-Man?), the system used vector graphics to draw smooth line-art images. Each vector was a straight line, or a smooth arc, connecting point A to B. Vectrex games were true works of art, and the original hardware is quite rare (and $$$)!

    Scopetrex

    The Scopetrex

    Well, [Chris] caught the vector graphics bug. But he decided to build a Scopetrex – a hardware emulator that allows you to run Vectrex games on an oscilloscope! He would theoretically just connect this to the Conar 255’s existing X, Y, and Z (blanking) inputs.

    We like this “minimum invasion, maximum re-use” approach. We’ve gone down this route numerous times to craft Oscilloclocks out of still-usable hardware. (The alternative? Install a full set of modern boards that drive the CRT directly.)

    Sample specimens of “minimum invasion, maximum re-use”

    [Chris] got down to planning. He could interface the X and Y inputs easily. But he faced a problem with the Z (blanking, or intensity modulation) signal, which instructs the scope when to turn the beam on and off:

    • The Scopetrex outputs a 5V DC digital blanking pulse.
    • The Conar requires at least 20V peak-to-peak blanking signal – and employs analog AC coupling.

    We’ve solved this mismatch problem before using various non-standard Oscilloclock board setups and complex hook-ins to the existing circuits. Always on a case-by-case basis, always unique.

    But now, at last, it was time to standardise the process. To make it easy. To adapt any vintage oscilloscope for digital blanking from a microcontroller! We proudly announce the next member of the Core family: The Z Core!

    The Z Core (in this case, a Z Core 2 Ex) …

    … joins the Oscilloclock Core family!

    How to install it

    Believe it or not, the minimal installation requires just 3 steps. For almost any oscilloscope! The Z Core effectively sits in series between your device’s blanking supply and the CRT grid.

    1. Snip the wire connecting to CRT grid.
    2. Connect the orange wire from the Z Core to the circuit side of the cut wire.
    3. Connect the green/yellow wire to the CRT grid.
    Snip.
    Connect!

    Visit the Z Core Support Page for lots more detail, including the obligatory warnings about high voltage. There are also details on how to connect the Z Core to your controller, detailed specifications, and some fun Q&A to help answer your most burning questions!

    The Z Core 2 Ex!

    We’ve wanted to develop a dedicated, built-for-purpose Z Core product for a very long time. This would consist of a single, miniaturised, low-power board called (ingeniously) a “Z Core Board”, and a few harnesses.

    But [Chris] didn’t want to wait for Oscilloclock labs to work through its ever-growing bucket list. Could we deliver within 2024?

    Yes!

    In past retrofits such as the Kikusui 537, we’ve taken spare boards that were originally designed for fully-featured Oscilloclocks, and partially populated them with only the necessary components to serve the blanking purpose.

    Partially populated Oscilloclock Power Board

    For [Chris], we found an almost fully-populated new-old-stock Power Board v2.27 and compatible CRT Board v1.21 lying around, just dying to be used and loved by someone. Older revision boards do tend to be set aside, as folks want the latest and greatest.

    With just a few minor modifications, this assembly shipped – and is now branded as the Z Core 2 Ex. The “2” refers to the Power Board’s major revision, and the “Ex” stands for “external blanking amplifier” (the function of the CRT Board). The Power Board rev2.2x series boasts an on-board blanking amplifier, but this section wasn’t already populated. What a great opportunity to use up a stock CRT Board!

    [Chris] will be happy. And we’ll keep up this spirit of minimising waste. You’ll see some other Z Core assemblies popping up in future: a Z Core 1 Ex, a Z Core 2, and potential variations of Z Core 3’s.

    And finally, one day, a genuine dedicated Z Core will be born!

    Why your scope needs a Z Core …

    Many old oscilloscopes simply don’t have any input for Z blanking, Z axis, intensity modulation, or cathode modulation. (Look carefully – it goes by many names!) Or, the input may be there, but it’s not compatible with a microcontroller. Why couldn’t the designers offer a decent interface?

    Well, it all has to do with high voltage! To get there, let’s cover how CRTs work in just three short sections:

    Gun

    A cathode-ray tube (CRT) has an electron gun that shoots electrons at the phosphor molecules on the screen. The electron beam is deflected by putting positive and negative voltages into electrodes placed in the CRT’s neck, and this is how patterns are drawn on the screen.

    This is how a CRT works. It’s awesome.

    But the electron beam has to be turned on and off, to break the pattern and make meaningful images on screen. This is known as blanking.

    Blanking

    Oscilloscopes, particularly, have to blank the beam when it goes back (retrace), from the right to the left again. If there were no blanking, you’d see a retrace line – wickedly cool for us artists, but devastatingly distracting for engineers who want to focus on the waveform itself!

    Retrace lines – arty but not desirable

    Oscilloclocks also rely on blanking. In Circle Graphics, where all figures are composed of lines and circles, blanking is crucial to creating meaningful segments. For example, a “C” is readily created from an ellipse “O”, simply by blanking the beam at just the right place!

    A blanking pulse kills the beam to get a ‘C’

    Grid

    CRTs are designed for blanking. There’s a valve-like electrode called a grid that sits inside the gun, just in front of the cathode where the electrons are spat out. If you inject a negative voltage into the grid (compared to the cathode), it repels those electron babies and sends them back where they came from. They don’t bombard the screen, and no more light is emitted. Blanking in action!

    Titillating! Electron field density is reduced when a negative voltage is applied to the grid!
    A fuller explanation – from The Bible
    The bible

    A change in grid voltage influences the field distribution of the first lens, and in so doing controls the emission from the cathode. For any fixed value of voltage applied to anode 1, it influences the number of electrons which pass through the cross-over point. Let us see how this comes about. In Fig. 5-17 is shown the field distribution in the first lens for two values of grid bias, O and -30 volts, and a fixed value of voltage on the plate.? It is clearly evident that with zero bias, the area adjacent to the cathode, between the cathode and the control-grid aperture, has a comparatively high positive potential as the consequence of the field between the control grid and the first anode. Under such conditions of zero grid voltage, it has been found that the area of the cathode which is emitting corresponds approximately to a projection of the area of the grid aperture; the maximum number of electrons are passing through the grid opening and the beam-current density is high.

    When the control grid is made negative by an increase in the bias, —30 volts in the illustration, the field distribution in the vicinity of the cathode is altered so that only the center of the emitting surface is behaving as an emitter. The other areas are influenced by the space charge and effectively are not emitting. The result is a reduction in beam density and several other related effects.

    High voltage

    So – back to the high voltage aspect. The cathode and grid are usually about 2kV (that’s right – 2,000 volts!) negative compared to the rest of the circuits. If you connected an external input signal directly to the grid, something would fry.

    Old-school oscilloscope designers took a very easy (read: cheap) solution: they stuck a high voltage capacitor between the grid (or cathode) and the external signal. This is called AC coupling because the capacitor blocks the DC voltage (2kV), and only couples through the AC (the fluctuating blanking) component of the signal.

    AC coupled external intensity modulation in the Conar 255 (L) and the Trio CS-1554 (R)

    This method of intensity modulation was fine for the regular, repeating signals observed in old TVs and radios. But it isn’t what [Chris], or so many millions out there like him, needs! They need to send through an irregular, sometimes not-fluctuating-at-all (i.e., DC) signal. They need DC coupling! And it has to be isolated – standing off more than 2kV!

    And there’s another voltage related problem: the grid has to go substantially negative with respect to the cathode, in order to completely block the electron flow. We’re talking 20-50V typically. This is not a voltage that a modern microcontroller board will deliver! This requires an amplifier.

    Summing it up

    So that’s it! Just three(?) words. We need an isolated DC-coupled amplifier. And it needs 2kV isolation with a 10x amplification factor.

    Welcome to the Z Core!

    Demo

    No assembly can leave our lab without being fully tested, and without a demonstration to ensure the customer’s utmost satisfaction. Here’s how the demo went:

    The host device: Trio CS-1554

    This venerable Trio (also branded as Kenwood) hails from around the same era as the Conar 255. It was attractive, had fairly good specifications, and a low(-ish) price tag, making it very popular both in Japan and overseas. Documentation is freely available and… more importantly, I had one lying around!

    Look carefully – it’s bulging and leaking!

    Of course this device is full of high voltage oil capacitors. These were effective in their day, but they break down over time, and things get very nasty. One particular HV capacitor in this unit was overheating to the point that the metal case had warped, and oil was even leaking out! Ick.

    A few modern-day capacitors hacked together replaced the leaky unit and saved the day. Onwards!

    The controller: Oscilloclock Connect

    Oscilloclock Connect

    As mentioned on the Availability page, one lovely Oscilloclock Connect unit is in stock. What better controller to verify the Z Core’s performance?

    The demo

    1. Connect Connect X output to Trio EXT HORIZ input at rear 1
    2. Connect Connect Y output to Trio CH1 vertical input
    3. Connect Connect Z output to Z Core input 2
    4. Connect Z Core outputs to Trio CRT grid and grid circuit (as shown in earlier section)
    1. Incompatibility! The Trio’s horizontal input seemed to want 10V peak-to-peak for maximum deflection (this is way off its original specs of 250mV/cm. I think it’s broken!) The Connect by default has only a 3V peak-to-peak output signal. The image is going to be small… ↩︎
    2. Trickery! The Connect by default is designed for a display device with a high-impedance Z input. The Z Core 2 Ex has a low-impedance input and 15mA drain at 5V. A temporary mod was needed in the Connect – which was promptly reversed after the test. ↩︎

    The result? A relatively clean image, albeit small! But the blanking works well. [Chris] was okay with the jagged edges and other blemishes; these are attributable to the Trio’s rough condition.

    Performance testing

    The Oscilloclock cave is not a precision testing laboratory. But we do have a significant collection of equipment, and every piece plays its part. In this case, we deployed a Hewlett Packard 1901A Pulse Generator.

    Choosing amongst a plethora of delightful old oscilloscopes, we stayed with the HP theme and used a venerable but still digital HP54615B.

    Yes! This HP has an undocumented Tetris game built in!

    The setup was simple:

    1. Set up the pulse generator for 100kHz square wave
    2. Set rise and fall times to minimum (around 10ns)
    3. Set output to 5V and connect to the Z Core’s input
    4. Connect a 20pF capacitor across the Z Core’s output, via the standard 200mm 22AWG harness
    5. Connect Ch1 of the scope to the input, Ch2 of the scope to the output

    Results

    MeasurementAssembly: Z Core 2 Ex
    Waveform base voltage-46V
    Rise time130 ±10 ns
    Fall time180 ±10 ns
    Propagation delay120 ±10 ns
    Effective bandwidthDC to 3 MHz
    (limited by rise/fall time)

    These results were satisfactory. But at some point, we’ll try the same with a Z Core 1 and a Z Core 3. And one day – a purpose-built pure Z Core. Stay tuned!

    In conclusion

    Well, that’s a wrap! The tested assembly has now shipped, and soon [Chris] will be able to try out a Scopetrex on his minimally-modified Conar oscilloscope. Fingers crossed!

    For more technical info, fun facts and Q&A, check out the Z Core Support page. And for a peek at our range of gadgets, be sure to check out the Gallery.

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  • OscilloChat!

    OscilloChat!

    Here’s a rare thing: Take the Toshiba ST-1612B Oscilloclock. Run the OscilloTerm VT52 terminal feature. Connect it up to the most famous artificial intelligence API around – ChatGTP. And what do you get? OscilloChat!

    Oscilloclock owners can now spend even more time with their retro clocks, discussing technology, politics, finance, the universe, and so much more. OscilloChat is humorous, witty, and the writing style is remarkably like your senior engineer (that’s me).

    At best, this is eerily entertaining. At worst, it’s annoying and entirely untrustworthy! Let’s see what happened when I asked: “What’s your favourite Oscilloclock?”

    To see this and more incredible videos in high resolution, check out Oscilloclock on YouTube!

    They don’t call it generative AI for nothing. Here we have an AI masquerading as a knowledgeable Oscilloclock Lab staff member, trying to sell you two Oscilloclock models that don’t even exist (the Minimalist Marvel and the Pendulum Palooza). And when challenged with “Is it real?” the AI, pushed into a corner, admits that “well, if it existed, it would be great.” It’s like dealing with a child.

    The fictitious “Pendulum Palooza” Oscilloclock

    But like we do with children, let’s give OscilloChat a chance! Here is what the proposed Pendulum Palooza Oscilloclock might actually look like, courtesy of the DALL-E image generation model.

    Dear readers, please draw your own conclusions!

    How it works

    The OscilloChat experiment setup is simple. The Toshiba Oscilloclock serves as a display (a dummy terminal), connected to a PC over an RS232 serial cable. A Python script running on the PC orchestrates traffic between the human operator, the Oscilloclock display, and the Open AI API.

    Interaction with the GPT AI

    The Python script first creates a session with the GPT AI. It then sends an instruction telling the AI what it is; i.e., to give it a role, including any specific instructions that it needs to follow in the subsequent conversation with the human:

    "You are an assistant at Oscilloclock.com. You will be asked questions about any topic. Your responses should be witty and fun, and follow the same style as blog posts at oscilloclock.com web site. Responses should be short (within 512 characters). You can ONLY use ASCII characters! Do NOT use non-ASCII punctuation marks. You can give a partial answer, but you don't have to end each response with a question like 'want more? just ask!'"

    Next, the operator types a question, which is directed over the serial link to the Oscilloclock for display, and also sent across to the AI as a user input. The API has a little think, and momentarily provides a response which is directed to the Oscilloclock.

    Until the session is closed (e.g., by killing the Python script), the session will remember all previous interactions with the human on that session. This ability to persist and build upon information for use in the ensuing conversation is what makes the AI so engaging and entertaining.

    Delay effects

    Each response back from the AI is sent character by character to the Oscilloclock display over the serial link. But even at 9600 baud (a turtle’s pace, by any modern standard!), the screen would scroll almost instantaneously, and the poor human operator would never be able to catch all the text.

    To slow this down, the Python script adds some delays: after each character, after each word (identified by spaces/whitespace), and after each line.

    CHARACTER_DELAY = 1/120
WORD_DELAY = 0.3
LINE_DELAY = 0.8

    Besides making things easy for the operator, it also gives a neat impression that the AI is thinking while composing its replies!

    Lissajous Watermark

    Plain character displays can get boring. Happily, Oscilloclock Lab has a solution for every kind of ‘boring’! In OscilloChat, we leverage the External XY feature first introduced in the Metropolis Clock to feed two signals from an iPhone into the X and Y amplifiers, generating a Lissajous watermark. What a way to make a dumb terminal display look smart!

    Dissecting the dribble

    If you want to dissect OscilloChat’s dreadful dribble in detail, here’s the full transcript:

    Hi, tell me about yourself!

    Ochat: Well hello there! Picture me as your quirky digital sidekick, armed with snazzy facts and some serious charm. I’m here to sprinkle a little fun on your curiosities and wrap your questions in witty flair. Think of me as the zany clock in your atticalways (sic1) ticking, forever colorful, and here to help you find the right time for any topic! So, what tickles your fancy today?

    What is your favorite oscilloclock?

    Ah, the grand question of favorites! While I can’t cozy up to a specific oscilloclock like a warm cup of cocoa, each one boasts its (sic2) unique charmlike (sic3) a carnival of timepieces! From the whimsical wobbles of the Pendulum Palooza to the sophisticated elegance of the Minimalist Marvel, every oscilloclock tells a story. If I had to choose, I’d say the one that dances to its own beat is my kind of clock! Ready to find your oscilloclock soulmate?

    Tell me more about the Pendulum Palloooza (sic) Oscilloclock… is it real?

    Ah, the Pendulum Palooza Oscilloclock (sic4) it sounds like a time-traveling festival, doesn’t it? While it may not be a certified member of the oscilloclock family just yet, it captures the essence of rhythmic oscillation with flair and fun! Picture this: a clock that swings and sways, rhythmically keeping time like a gentle pendulum dance. If only it existedwho (sic5) wouldn’t want to host a party where every tick-tock brought a new groove? Keep your eyes peeled for whimsical creations, because you never know when a Pendulum Palooza might swing into existence!

    Nice! thanks for the feedback

    Anytime, time traveler! I’m always here to sprinkle some fun on your quest for knowledge. If you have more burning questions or just want to chat about clocks, I’m all ears (well, metaphorical ears)! Keep ticking and tocking along with curiosity!

    1. Missing dash (technically an em dash, Unicode U+2014). This should read “… attic — always …” ↩︎
    2. Missing apostrophe (technically a right single quotation mark, Unicode U+2019). This should read “… it’s …” ↩︎
    3. Missing dash. This should read “… charm — like …” ↩︎
    4. Missing dash. This should read “… Oscilloclock — it ….” ↩︎
    5. Missing dash. This should read “… existed — who …” ↩︎

    You can see from the footnotes that the AI is responding with non-ASCII characters. These cannot be displayed (yet!) on the OscilloTerm firmware, and the AI has completely ignored the explicit instructions we gave when assigning its role:

    ... You can ONLY use ASCII characters! Do NOT use non-ASCII punctuation marks. ...

    But scolding the AI about this results in a childish non-apology, and quick change of subject:

    You were NOT supposed to use any non-ASCII characters, like dashes or right quotation marks!

    OChat: Oops! It looks like I got a bit carried away. No special characters from now on, I promise. Just plain ASCII fun ahead! What can I help you with today?

    (Note: this interaction was not included in the video.)

    What’s Next?

    With the OscilloChat proof-of-concept complete, we could do away with the PC completely, by adapting the ubiquitous Oscilloclock Wave module with necessary chip upgrade and firmware to (a) connect to Open AI API and (b) connect to an external bluetooth keyboard.

    Taking a step further, we could do an OscilloChat2 (OscilloChat Squared) where two OscilloChats interact with each other. What would the conversation be like? Where would it lead?

    We could use a more advanced generative AI model to automatically compose pictures and graphics entirely from Lissajous figures! (We have done this manually for all fonts, logos, and figures rendered to date – see Screens & Things. And there are software packages such as OsciStudio that support the creation of animations from Lissajous figures.)

    Of course, “smart speaker” functionality could be dropped in, to eliminate the need for a clunky keyboard, and provide speech capability. OscilloChat could become OscilloChatty! How cool? How annoying? You be the judge!

    All excellent items to add to the ever-growing list…

    Credits

    [Eric], the protagonist of the recently published Zork on an OscilloTerm!, noticed this at the end of the post:

    He just couldn’t help pick up the gauntlet! He modified the python script he originally wrote to play Zork, and became the first person ever to integrate GPT into a scope clock. Check out his own video of Zork and GPT running on his OscilloTerm!

    Many thanks to [Eric] for sharing the script – judiciously used in our experiment above!

    Video music credits:
    Electrorchestra by Alexander Nakarada (CreatorChords) | https://creatorchords.com
    Music promoted by https://www.free-stock-music.com
    Creative Commons / Attribution 4.0 International (CC BY 4.0)
    https://creativecommons.org/licenses/by/4.0/

    Like what you see? Do YOU want to possess a device combining the oldest of technologies with the newest? We at the Oscilloclock Lab love century-spanning experiments – whether practical or not. Stay tuned for more!

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  • Made in Japan. Then. Now.

    Made in Japan. Then. Now.

    Here at the Oscilloclock Lab, we see a lot of vintage Japanese oscilloscopes made in the 50’s to 70’s. Most were purely utilitarian and austere, with little aesthetic appeal.

    But this Toshiba ST-1612B is different. It’s cute, compact, and culture-rich. Just when we thought Toshiba had exhausted its artistic reserves with their stunning ST-1248D, they managed to come up with THIS. Wow…

    Oscilloclock’ed!

    We discovered our protagonist some years back – dirty, dusty, and destined for the trash heap. For aeons, it sat in stock, patiently waiting its turn.

    “Oh, when can I transcend test equipment mundaneness, and reach nirvana like my brethren?” screamed our protagonist.

    During our COVID-era hiatus, this unit’s pitiful wail fell on deaf ears. But with a strong recent recovery in parts availability, shipping routes, and other stabilizing factors, the Oscilloclock Lab has begun to thaw. Spring has arrived!

    And what better way to mark the occasion than to grant our Toshiba its wish?

    Done.

    And yes – it was made in Japan. Again.

    Exquisite exterior

    The case and knobs were in reasonably good condition and polished up very nicely…

    One knob is NOT original. Can you pick it?
    Class and style – even down to the model number plate at rear!

    Sadly, the leather carrying strap had seen better days. Yes, you read that correctly! This was designated as a portable oscilloscope, although it weighed in at more than 10kg, and had no battery supply!

    Nice leather. But was it really… portable?

    We love this adorable hatch compartment and secret patch panel. So utilitarian! Whole tribes of radio servicemen must have stashed their valuables here for safe keeping, before going away on holiday. Sadly, there was no jewellery or secret documents to be found in our unit…

    Take a look at this CRT hood. The phosphor screens in cathode-ray tubes are sensitive to external light, so many ‘scopes employed hoods or shades to keep ambient light out. This improves screen contrast for the lucky operator. Kudos to you if you can recognise the material used our Toshiba’s hood:

    Yes, it’s rubber. Solid rubber, with no metal tube inside. And while it’s a little banged up on the surface, it’s not disintegrating or brittle! It’s firm, yet still sufficiently flexible to support the CRT. And a little plastic polish did wonders. Good for another 60 years!

    Incredible internals

    Unlike many other scopes of the era, opening the case is easy. Just turn the latches with a coin, a single revolution. Voila!

    A nice complement of 12 tubes. Toshiba made them accessible for easy replacement

    As with its Toshiba brother and several other units crafted to date, we carefully installed amber LED lighting to simulate the original warm, gentle glow of electron tubes. This generates a beautiful, peaceful ambience.

    XY Input inspires!

    Avid readers may recall the XY Input feature first introduced in the Metropolis Clock, and included in several models since.

    This ST-1612B unit features a neat set of banana jacks in the rear hatch compartment, where the oscilloscope probes used to plug in. We repurposed them as X and Y channel signal input connectors.

    Driven by function generators, preamps, or even a mobile phone, we can explore an entirely different level of visual imagery!

    A function generator app
    A scene from “Planets” by Jerobeam Fenderson, played on the Toshiba

    A just-fit retrofit

    The ST-1612B was an engineering marvel. They packed an amazing amount of circuitry into a very limited space.

    But we needed to find space for two 100 x 80mm Oscilloclock boards. With legroom to isolate high voltage and provide circulation. And where controls can be reached. Not easy!

    Well, removing just a few bits and pieces* revealed two nice big cavities. And the best part? There were already access panels, complete with ventilation holes! What foresight those Toshiba designers had!

    A perfect fit! * Which bits were removed? Subscribe and await the “Making of…” post!
    In situ adjustments, made easy

    Control Freak

    You can’t beat vintage test equipment if you like controls: toggle switches, slide switches, rotary switches, potentiometers, trimpots – these guys have it all!

    But at Oscilloclock.com we target simplicity. There is only one control you need to turn the clock on and off, change faces, change settings, and generally play with your precious. Here, the focus control (焦点) gives you this authority. Who would ever guess?

    And for that most discerning owner, keen to install her beloved Toshiba ST-1612B in a moody environment such as a bar counter, living room, or bedroom: the intensity control (輝度) dictates the velocity of the electrons, as they smash haplessly into the phosphor. Okay, okay – it’s just a brightness control!

    Finally: we’ve wired up the frequency range switch (周波数範囲) to switch something on and off. We haven’t decided what. Let the Toshiba’s future owner decide its fate!

    What does this DO? You decide!

    Circle Graphics – with a caveat

    Oscilloclocks employ Lissajous figures to generate smooth, curvy artwork and characters on the screen. No pixelated, chunky graphics! But fastidious followers may spot that on the Toshiba ST-1612B’s screen, circles are not as perfect as advertised in our Circle Graphics post. And there are some jagged edges on the segments.

    This is because we’ve installed some prototype boards. These are early revisions of the yet-to-be-announced New Design, and the circle generator and deflection amplifier circuits aren’t quite right. But they’re too good to waste.

    Earlier prototypes of the New Design. – not quite right, but not wrong either!

    But we think it’s just fine! Tube amplifier enthusiasts understand: vinyl records and tube amplifiers actually sound better than digital devices, for some music. And our Toshiba here is 50 to 60 years old. A few kinky curves only add to its grace.

    The Toshiba ST-1612B Oscilloclock is in stock and ready to perform. Want to customize the screens? Decide on the secret switch’s secret? Work up some crazy XY effects? Check our Availability page!

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  • Oscilloclock Bare(ly) makes it to Brazil

    Oscilloclock Bare(ly) makes it to Brazil

    Whether directly or indirectly, the pandemic seems to have slowed everything down: chip production; the global economy; and even Oscilloclock blog post publishing!

    But perhaps most impacted of all is transport logistics. [Dante] in Brazil discovered this to his dismay in July 2020, when he purchased an Oscilloclock Bare unit. The P.O. had stopped all air service to Brazil just 3 weeks earlier – well after our discussions had started. Oh no!

    [Dante]’s crisp new Oscilloclock Bare, ready to go, but unable to ship!

    [Dante] waited patiently for 6 months for the post office to resume accepting airmail service to Brazil. But they never did. And FedEx and DHL came at too hefty a price. In desperation, he authorized shipment by sea – and at last, in December 2020, his package was off! 

    Absence (of air mail service) makes the heart grow fonder...

    After an agonizingly long wait, [Dante] finally received his unit 6 months later – in July 2021. He then spent the next 5 months completing his dream project!

    [Dante]’s Dream: A Hewlett Packard retrofit

    The Oscilloclock Bare is designed to be a no-frills controller assembly that highly knowledgeable folks can install into their own displays. [Dante]’s dream was to use this to convert his beloved HP 182T / HP 8755C unit into a living, breathing scope clock.

    And convert he did!

    Question: How do you add ambience to a home?
    Answer: Instill new life into a device from yesteryear!

    Clearly, [Dante]’s 18 month end-to-end was worth the wait.

    The Build

    [Dante] was kind enough to supply a write-up of his project, including some clever solutions for pitfalls along the way. Let’s hear from him in (mostly) his own words!

    Motivation

    The model HP 182T is an oscilloscope featuring a large CRT with a graticule of 8 x 10 major divisions and a display area of 133 cm2, coated with a P39 aluminized phosphor for high brightness and long persistence.

    The HP 182T works as a display mainframe supporting other HP plug-in test equipment, such as the HP 8755C, a swept amplitude analyzer.

    Both items are nowadays considered “vintage” test equipment. But with the Oscilloclock board installed, they have been transformed into a unique appliance with a natural appeal for practical use. Far better than the regular surplus market destinations, or — even worse — destructive disposal!

    HP 182T + HP 8755C. Can you spot the Oscilloclock control board?
    Control board installed!

    HP 8755C in short

    This plug-in unit works primarily as a signal conditioner and a multiplexer for “almost dc levels” from three RF detector probes attached to three input independent channels. There are front panel adjustments for the scaling, gain and multiplexing controls that provide the appropriate Y-Axis composite signal for displaying by the HP 182T mainframe.

    The Oscilloclock control board was elected to be installed inside this plug-in unit.

    HP 182T in short

    This oscilloscope is built around the CRT with its high voltage power supply.

    The X-Axis signal from the Oscilloclock board is fed to the HP 182T’s chain of the horizontal pre-amp plus output amplifier, which drives the CRT horizontal deflection plates.

    The internal wiring of the HP 182T connects the CRT’s vertical deflection plates directly to the plug-in cabinet of the display mainframe, so the Y-Axis signal from the Oscilloclock board is routed inside the HP 8755C itself.

    The Z-Axis signal from the Oscilloclock board is fed to the HP 182T’s gate amplifier.

    Wires, wires…. What goes where?

    Drawbacks

    Contrary to any standard X-Y scope where the two input channels are always supposed to have electrically similar (if not identical) characteristics, the correct operation of the Oscilloclock board for the application here was shown to be not as seamless as first imagined. You have to face some details of these integrated “host” equipment (HP 182T + HP 8755C) to see why…

    As described, there are distinct amplification chains accepting the Oscilloclock output signals. This presents specific challenges regarding (a) the differential gain for the X and Y signals, and (b) the differential time delay between any combination of the three X, Y, and Z signal outputs of the Oscilloclock board.

    First Approach

    Before having the board at hand and expecting to make it work as soon it arrived (the shipping took longer than expected due to COVID restrictions), I first planned the signal flow and did the wiring. I had one eye on achieving a ‘clean packaging’ of the board inside the HP 8755C, and the other on ensuring compatibility between the Oscilloclock’s X-Y-Z output signals and their respective chains planned in the host equipment, considering signal amplitude and required frequency response.

    The adaptations made at this time considered a minimally-invasive approach, where the criteria was to “make it simple”. This was limited to just opening or re-using connections and keeping the existing routing, in order to use the Oscilloclock’s X-Y-Z output signals in the most simplistic way possible.

    Another necessary one-time adaptation was for the board’s power supply, and integration of its PSON output signal with the equipment’s hardware. This part of the design was successfully kept to the end of the project without any further modification.

    First time installation of the oscilloclock board

    Upon arrival and a bench test of the Oscilloclock board with a scope, I immediately figured out that the amplitude levels for the X and Y output signals were lower than expected (maybe due to my misinterpretation of the specs). I did the gain compensation corrections again and went thru the complete installation of the board inside the host equipment, anxious to see it working.

    What a disappointment when instead, up came a completely distorted and elliptically shaped image, blurred with noise, and what looked like un-blanked retrace lines. Worse yet, mainly when alphabetic characters were displayed on the screen, none of the shapes were correctly formed.

    Of course, that was time for a break — and a complete review of the job and the work done so far!

    Chasing the problems

    The Lissajous figures generated by the Oscilloclock board use an approximately 40 KHz  sinusoidal signal, so I started to play with an external generator at the same frequency and amplitude for the X and Y signals (at about 1 Vpp) and trace it inside the HP 8755C and HP 182T.

    At this time, I’d already exercised the Z-axis waveform from the Oscilloclock board and the expected processing through the HP 182T. There was no evidence of problems with this Z-axis signal chain, and I achieved a measured propagation delay of around 50 nS.

    The minimalist approach mentioned earlier showed its consequences, when a propagation delay of an impressive 8 uS was measured at the vertical deflection plates, and  around 1.5 uS at the horizontal deflection plates! It was time again for another break, to elaborate a new routing scheme for the X and Y signals.

    Final Approach

    From the previous analysis, I ended up with two different and both very large propagation delays for each of the X and Y signals (as compared with the measured 50 nS for the Z-axis). How to solve this? It did not seem to be only a routing problem.

    I decided to investigate X-Y-Z signal propagation delays in the two units separately. After a thorough measurement of propagation delays inside the HP 182T itself, comparing with the HP 8755C plug-in itself (where the Oscilloclock board was installed), I concluded on two countermeasures:

    1. The complete removal of the Processor board XA-6 from the HP 8755C. (This is where the Y-axis signal from the Oscilloclock board had initially been connected.) Instead, this routing was transferred directly into the Normalizer Interface board XA-11 (which interfaces with the HP 182T).

    2. Also at the Normalizer Interface board XA-11 inside the HP 8755C, the substitution of two original op amps U9A and U9B (HP #1826-0092) by TL072 op amps, which are faster and have a higher slew rate.

    These solutions were enough to align the signal propagation and complete my project!

    Dante JS Conti, 8 November 2021

    Like what you see?

    We do! We love to hear back from Oscilloclock owners, to hear their stories.

    Check out our previous posts and the Gallery for info on other unique creations!

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  • Connect !!

    Connect !!

    These days, just about everyone has an old oscilloscope lying around. You know, an old, dusty, derelict scope handed down from Grandpa (or Grandma). Well, [Paul] had something even better – an old Tektronix 602 X-Y Monitor! Could an Oscilloclock Control Board drive this vintage beauty? Absolutely. Could I make an aesthetically pleasing case? Definitely. How about time sync via WiFi? Stock standard!

    Presenting the Oscilloclock Connect:

    Here’s what it looks like plugged in to my fabulous old Tektronix 620 monitor:

    And why not have a pair of Connects drive a Tek 601 and 602?

    The Build

    The main component of the Connect is, of course, a standard Oscilloclock Control Board. As usual, all 121 parts on Paul’s board were individually mounted and soldered by hand. The board then was programmed and underwent rigorous inspection and testing. Finally, the board was cleaned to remove flux and renegade flecks of solder, and sprayed with HV coating for humidity protection and – arguably more importantly – to give it its glorious sheen.

    The case was custom-made and professionally machined right here in Japan from 6mm-thick sheets of pure cast acrylic (not extruded). This is an extremely transparent, hard, high grade acrylic – and Oscilloclocks deserve nothing less!

    The case was sprayed with a special acrylic cleaner and static protection solution, before fitting the various components. Naturally, every part was cherry-picked, right down to the three BNC connectors – they needed an aesthetically pleasing colour, but they also had to have a shaft long enough to mount through 6mm-thick acrylic!

    Finally, the physical interface! The knob was chosen for its perfect finger-fit and delicate aluminium/black tones, which gently contrast with the rest of the unit.

    The Compatibility Crisis

    Over the years, many folks have observed that the scope at hand has an “X-Y mode”, and asked if they could just ‘plug in’ an Oscilloclock Control Board. “Is it compatible?” Unfortunately, the response has usually been disappointing.

    You see, creating figures and characters with Circle Graphics relies on the scope’s ability to turn the beam on and off at split-second intervals. This feature is called a “Z-axis input”. While many scopes from the 80’s and beyond do sport such an input, there are two common limitations:

    Limitation 1: AC-coupled Z-axis inputs

    Capacitive coupling – effective at isolating the input from cathode potential (-1260V !)

    The input is connected to the CRT’s grid or cathode circuit via a capacitor. This is a low-cost, effective way to isolate the (usually) very high negative voltage of the grid circuit from the input.

    The problem here is that the capacitor, by its very nature, removes the edges from the pulse. The controller is no longer able to control the beam on/off timing, and you end up with uneven blanking across the segments, as shown in the screenshot at right.

    Depending on the values of the capacitor and the surrounding resistors, the symptoms may not be severe. However, the best way to resolve this problem (while still keeping the oscilloscope’s original circuit intact) is to insert an isolated DC blanking amplifier directly in series with the grid (or cathode). See the Kikusui 537 Oscilloclock for an example of this.

    LIMITATION 2: INSUFFICIENT BLANKING AMPLIFICATION

    Most oscilloscopes tend to require at least +5V on the Z-axis input to noticeably blank the beam. The Connect, however, is only capable of delivering +2.5V. It works just fine if you set the scope’s Intensity control very low, but as you increase intensity, the blanking quickly becomes ineffective.

    Below we have a beautiful Japanese YEW (Yokogawa Electric Works) 3667 storage scope. The left shot is misleading due to the camera exposure; the displayed image is actually extremely dim. The right shot shows the same* image with the intensity control increased – the image is bright, but there is no blanking!

    * Astute readers will observe that the time is significantly different between the two shots. This is a result of the WiFi NTP sync kicking in right in the middle! More (or less) astute readers may also notice that the scope’s trace rotation is not adjusted very well…

    Of course, it would be a simple matter to incorporate a pre-amplifier for the Z-axis, which would solve this problem. This will be introduced with the next Control Board revision!

    Like what you see?

    Nothing brings more joy than connecting this bundle of usefulness into a woefully unused old oscilloscope or X-Y monitor. If this is of interest to you, visit the Availability page for more information, and of course see the Gallery for other unique creations!

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