Zork on an OscilloTerm!

Posted on 2024/06/15 by Aaron

Today’s story began with a mail from [Eric], who’d read up on the Oscilloclock 3-inch VGA Assembly and wondered if it could be used to create an old-school serial terminal display on a vintage oscilloscope CRT.

Yes it could! In fact, the Oscilloclock Lab did one better. Instead of just a VGA display controlled by an external device, we developed native terminal firmware that accepts DEC VT52 compatible commands over a serial port, and renders all text and graphics using beautiful, curvy Lissajous figures.

The stuff of dreams. The OscilloTerm Exo B7S4.

Demonstrating basic terminal features, connecting to a PC via serial cable

Oh, did I mention? It’s a clock as well!

Zork, anyone?

Ultimately, [Eric] just wanted to play Zork. And together we made it happen.

The CRT. The Case.

[Eric] wanted a sleek ‘skeleton’ look. His choice of a gorgeous B7S4 CRT, mounted in custom-machined cast acrylic supports, exposes all glassware and allows for a titillating rear viewing experience.

CRT rings and supports – originally introduced for the Oscilloblock “Summer Dusk” edition

And with a high-transparency cast acrylic case housing the electronics, the OscilloTerm Exo can be enjoyed from every angle!

Astute readers may wonder about the 2.1 kilovolts of high voltage coursing through their innocent-looking device. Rest assured! All internal wiring is sealed off, and Oscilloclock CRT harnesses are hand-crafted with heavy insulation and precautions taken against dust, prying fingers, rats, and even salivating cats.

Safety in action! Mil-spec connector (left); custom-designed acrylic cap on the CRT connector (right)

An O-ring blocks dust from entering the CRT/socket gap (picture from the Oscilloblock)

This case and CRT mounting variation is branded the Oscilloclock Exo, and has proven its wow-factor at several public exhibits to date. We certainly love it, and [Eric] did too!

The Terminal.

This post would never be complete without showing you what real serial terminals from the 1970’s looked like, and explaining what they actually did! Here goes…

DECscope VT52 (1974)
_{ClickRick, CC BY-SA 3.0, via Wikimedia Commons}

Terminals such as the above were physical input/output console devices, back when computers were the size of massive refrigerators, and the operator would sit remotely – at a desk in a separate area, or even a different room.

_{Gregory Lloyd, CC BY 2.0, via Wikimedia Commons}

The terminal and the remote computer were connected via a cable, and would communicate each other by sending data back and forth across the cable; mainly terminal commands and ascii encoded text. Most commonly, a serial communication protocol was used to get the data safely from one end to the other – and hence the devices were known as serial terminals or even serial consoles.

Amusingly, they were also called dumb terminals, because they had no computing power of their own; they were only extensions of the computer to which they were connected.

The OscilloTerm Terminal.

[Eric] wanted a special Oscilloclock that he could also operate as a terminal, connecting it to a remote computer via cable. The remote computer would control the display, using the same serial protocol and commands as an ancient dumb terminal.

But an Oscilloclock is anything but dumb. [Eric] wanted to keep all the standard exciting screens and features of his Oscilloclock active, and only display the special Terminal screen when the remote computer started to send commands. Then, when the commands stopped, the Oscilloclock should go back to the screen it was on!

His wish was our command! Here’s a demo of smart screen switching in the final product:

Some technical Comments

Naturally, the terminal emulator firmware was written entirely in assembly language.

PIC18F2680 – the Oscilloclock workhorse.

We use assembly mainly because the minimalist PIC microcontroller used in the current Control Board revision has only 64K ROM, and an unbelievable 3328 bytes (yes, BYTES!) of RAM. To squeeze all the lovely Oscilloclock features in, while driving Circle Graphics real-time processing, the code and memory space has to be clean, tight, and heavily optimized at the machine code level.

Assembly. It’s the ONLY way to squeeze it all in!

For even more technical details, such as the list of VT52 (and VT100) commands supported by the OscilloTerm, and the various configuration parameters that can be tweaked to make the terminal emulator more ‘friendly’ when connecting to a specific device, check out the Support page. Worth a visit!

Why Zork? And HOW?

Zork is an interactive adventure game. But it’s old. And it’s text-based, because it was run on computers long before fancy graphics capabilities were widely available. The player explores mysterious locations, solves puzzles, and collects treasures while avoiding various hazards and creatures. All by reading text and typing commands and responses!

[Eric] was able to play Zork by loading the game’s Z-code into a Z-machine interpreter known as Frotz, on a PC connected to the OscilloTerm. But there was trickery involved!

He had to recompile a version of dfrotz (the dumb terminal version of frotz) to remove the status bar and audio from the game.
He needed to wrap the dfrotz output with a custom Python script to support the OscilloTerm’s 16×8 screen and simulate the required baud rate.

But now that’s done, he can play any Infocom game that runs in dfrotz on his OscilloTerm!

What’s next?

Readers would probably agree that adding a generative AI feature would be incredibly cool. For example, the War Games feature is great, but the text on the screens is all pre-programmed. What if you could interact more naturally with your Oscilloclock?

Another one for the list!

Are you a serial serial terminal collector? Do you want to play Zork on the oddest device imaginable? Or, you fancy a clock in the Oscilloclock Exo range? Contact us and let us know!

Building the Astro Clock

Posted on 2023/05/27 by Aaron

In the last post, we took a look at a funky new sidereal clock from the Oscilloclock Lab. Now let’s take a look at what fanciness went into it!

The Hardware

[Alan], our astronomer protagonist, wanted to install all the electronics inside his Tektronix 620 X-Y Monitor. He didn’t need a nice fancy case.

Demonstration of a Lissajous circle — No pixels here! Circle Graphics

No problem! We supplied the Oscilloclock Bare – our stand-alone controller board that generates images and text rendered in smooth and silky Lissajous figures.

The board ships on a cast acrylic mount to make it easy to test externally, prior to installation into the host piece of equipment.

Next, we added the Oscilloclock Wave. This is a Wi-Fi adapter that allows an Oscilloclock to pull (Solar) time from NTP servers over the internet, keeping accurate time indefinitely.

For [Alan], we left the cabling and aesthetics options open, and shipped the basic Wave Core module instead of the stand-alone type pictured above.

Finally, we included a decent quality power pack, to allow running the assembly prior to installation.

This would eventually be eliminated by powering the unit from the Tek 620’s internal supply itself.

The software – Sidereal time enhancements

To transform the Oscilloclock Bare into the astronomically great Astro Clock that it is today, we needed sidereal time.

Easy! The US Naval Observatory Astronomical Applications Department provides a publicly available API for querying sidereal time, given a location.

The Oscilloclock Wave already had features to pull earthquake data from a similar API and push it to the Oscilloclock for display. Extending this for another API wasn’t astronomically difficult.

The Wave sports a bunch of advanced settings for particularly tweak-loving oscillofans out there. We just needed to add a few more! These are to enable querying and sending sidereal time to the Oscilloclock, and to set the location.

But why not just calculate sidereal time?

Some readers may have guessed that formulae and code libraries for calculating sidereal time are readily available. Why didn’t we just implement the calculation in code, and avoid depending on an external API?

Our minimalist PIC 18F2680 even had a terrible bug at one point…

Well, I’ve mentioned before that the current revision Oscilloclock Control Board uses a minimal-specification microcontroller with very limited capabilities, and is heavily optimized by coding in assembly language.

Sadly, this chip was already jam-packed to the hilt, and there simply wasn’t any more space left for the code and run-time memory needed to calculate sidereal time internally.

And writing the necessary floating-point calculations in assembly would be no mean feat!

Why Assembly Code?

Because We Can.

But, it sure ain’t easy…

So NO – we couldn’t easily calculate sidereal time, and it was API Option full steam ahead!

Astro Screens!

Even with its minimalist microcontroller chip, we’ve managed to squeeze some amazing stuff into the Oscilloclock Control Board firmware.

For more of the weird and wacky, see Screens & Things!

For this build, we needed yet more screens.

First, we used our trusty Figure Creator software to render a rudimentary telescope into Circle Graphics sprite code.

From a sketch … to … assembly code! Voila!

We then crafted a simple Astro Clock splash screen, by adding some random circles for stars and laying out basic text around the telescope.

Finally, we added some basic digital and analog clock screens, using the same telescope figure as a centrepiece. This was mostly straightforward, but the existing clock hand drawing code did need some tweaking, to reference either solar time or sidereal time depending on the active screen.

Done!

Invoiced. Paid. Shipped. Received. Treasured forever. Right?

Wrong!

Sidereal really sidelined…

A year after [Alan] received his lovely Astro Clock, the unhappenable happened. The Astronomical Applications API was taken down!

“undergoing modernization”… a harbinger of API death! Jan 2020 snap courtesy archive.org

The site was taken offline for a planned six months, for “modernization”. [Alan]’s sidereal clock was relegated to a normal solar Oscilloclock, albeit temporarily.

Astro Clock features relegated. Utter sidereal sadness

But as lovers of electron beams striking phosphor, we always look at the bright side! Six months is still relatively short in astronomical terms! We resignedly marked “X” on the calendar, and bided our time.

But then… the unfathomable fathomed. The COVID-19 pandemic struck. The USNO site modernisation was completely halted – very likely deprioritised in the midst of indiscriminate illness, clinical chaos, and staff shortages.

Halted… 2 years later, still no luck… Mar 2022 snap courtesy archive.org

We waited, and waited, and waited. There were no fingernails remaining to chew when, after two and a half years, a revised API was finally made available at the end of 2022. Hooray! Thank the stars!

API resurrected

Fresh API documentation in hand, we set about modifying the Wave to use the fresh fruits of the USNO modernisation machine.

Fortunately, there were only minor changes to the API – a few more mandatory data fields, a change in date format and such. These required a relatively small amount of rework in the Wave’s firmware.

And … we were back in the amateur astronomy business.

Almost like a big Christmas present from Santa!

Was this [Alan]’s Christmas present? – Santa in your Clock

Do we regret taking the API approach?

It’s a good question. API death could happen at any time – possibly rendering the Astro Clock lifeless, listless, or lethargic yet again.

But, no. The decision not to calculate internally was valid, based on the known constraints. And we did our veritable utmost to revive poor [Alan]’s Astro Clock as soon as possible.

By the way, we at the Oscilloclock Lab certainly can’t complain about USNO’s API shutdown. We, too, have been heavily impacted by pandemic and other worldly events. As of this posting, our formal activities, too, remain on pause…

… for now!

Curious about other Oscilloclocks that use APIs? Check out the AfterShock Clock, which taps into an earthquake API to display earthquakes in (almost) real-time on a lissajous-rendered map!

Astro Clock

Posted on 2023/05/14 by Aaron

A few years ago, we introduced Metropolis Time, a time system based on the 20-hour, two-shift days featured in Fritz Lang’s iconic movie Metropolis.

Since then, we’ve received a few requests to craft clocks that display some other calendar and time systems – from the ancient and archaic, to the religious, to the scientific.

That’s Astronomical!

Today’s exciting story began with a request from [Alan], a prominent amateur astronomer. He happened to have a lovely Tektronix 620 X-Y Monitor lying around, and wanted to turn it into a clock.

Well, that would be easy – the Oscilloclock Bare is a bare-bones controller assembly that can be used to drive an oscilloscope or XY monitor that meets certain requirements (for the techies: a DC coupled Z-axis amplifier). And the Tek 620 is perfect – wonderfully performant, and perfectly compatible. Job done! Right?

Oscilloclock Bare + Tek 620 + scientific passion = Astro Clock!

No way! [Alan] didn’t want just any old clock. The custom splash screen above was pretty cool, but could his clock display something called “sidereal time“?

Yes! Anything is possible, and here’s what we ended up delivering: several custom clock faces showing sidereal time (in both analog and digital formats), in addition to all the standard screens that are based on solar time.

But what is sidereal time?

A Solar day

Well, most normal human beings and their clocks like to measure a 24 hour day by using the Sun as a reference point. One solar day is the time it takes for the Earth to spin on its axis enough and see the Sun at the same height in the sky as the previous day.

For example, let’s say it’s 1 May 2023. It’s lovely weather out, and you happen to notice that the Sun reached its highest point in the sky at 12:30 pm. The next day, 2 May, you would find the Sun at its highest point at — you guessed it! — 12:30 pm. And if you ignore man-made tweaks such as daylight savings, you find the Sun is always at its highest point at 12:30 pm*, year-round, looking from the same location.

*This is not quite true – because every day is slightly shorter or longer. But it averages out over the year.

A sidereal day

Sidereal time, on the other hand, uses the distant stars as a reference point to measure 24 hours. One sidereal day is the time it takes for the Earth to spin on its axis enough to see the same distant star at the same height in the sky as the previous day.

Because the Sun is so close, and a distant star is so (relatively) far, there is a difference in the length of a sidereal day compared to a solar day. A sidereal day turns out to be approximately 23 hours, 56 minutes, and 4.0905 seconds.

Confused? I don’t blame you. This video should help:

History and Sidereal clocks

According to this brilliant post, the concept and utility of sidereal time has been around a very long time. The length of a sidereal day was even calculated to a surprisingly high level of accuracy some 1,500 years ago!

Here are two surviving sidereal clocks that were made “recently” – just a few centuries ago.

But who on Earth would use sidereal time?

Astronomers would.

Most people don’t look at the boring old Sun all the time. We look out to the stars and galaxies far, far beyond our solar system. If an astronomer wants to track the position of Betelgeuse day after day, she can record the sidereal time that she saw it, and know that it’ll be at the same ascension at the same sidereal time the following day. Brilliant!

Mariners and Astronauts would.

They can fix their location even when the Sun is not visible, by observing the position of the stars and calculating their position back from the current sidereal time. Life-saving!

Oscilloclock Labs would.

Because we can.

In the next post, we’ll take a look at the build. What hardware went into this Astro Clock? How on earth does it tick? Can you figure it out?

Garmin “puck” USB adapter – Finale

Posted on 2023/03/25 by Aaron

In the first post in the series, we looked at the Garmin 18x LVC “puck”. We talked about a particularly insidious issue that affected [Andrew] – both of his GPS units. And we saw that Oscilloclock owners really need to be able to update the firmware in these units.

In Part 2, we went through the design of an Oscilloclock Garmin 18x USB Adapter, that would allow the GPS to connect to a PC where the Garmin software runs to upgrade the firmware.

Now we conclude the series, with a treatise on the construction of the Adapter. Enjoy!

The final design

Here’s the design we arrived at in the last post. Let’s go through the steps to build it!

Fish out Fake Chips

TTL serial to USB adapter – watch out for fakes!

The key component required is a decent TTL serial to USB adapter with programmable inversion on the signal lines. But here we have to careful: many low-cost adapters out there are built around fake FTDI chips!

As mentioned before, we at Oscilloclock are pacifists. But if we were to wage war against anything, it would be fake components. They are unsafe, unreliable, unworkable, and entirely unethical. You get what you pay for, if you pay the right people. The people who design, manufacture, and support the real McCoy.

Besides ethics and reliability, there is also a practical reason we must avoid adapters based on fake FTDI chips – often the fake chips are not programmable. A true no-no. So watch out.

Program the inversion

FTDI provide a nifty utility called FT_Prog. Below shows the utility running on a PC with the adapter connected, and configuring to invert the transmit (TXD) and receive (RXD) signals.

Is it complicated? No – quite the *inverse*!

Dividing the input signal

We need to figure out the most elegant way to install the voltage divider – the two resistors we described earlier that reduce the impact of noise.

The cleanest way seemed to be to install the 1.2k shunt resistor directly across the receive and ground pins in the adapter itself, as below.

What about the 270 ohm series resistor on the RXD line? Well, installing this inside the adapter unit itself would require cutting tracks on the PCB. And that would compromise our effort, reliability, and aesthetics goals! So instead, we’ll insert this into the cable later on.

Cable Connector Conundrum

Recall that [Andrew] has two Garmin 18x units – one fitted with a small GPS connector and the other with a large connector. Wiring up two independent cables would have been natural. However, the TTL Serial to USB adapter came with only one cable pre-fitted with the necessary “DuPont” (a.k.a. Qi or 2550) connector.

DuPont, Qi, 2550 – they look low-cost but… Read this excellent writeup and weep

What’s the big deal? Surely we can just attach a Qi connector to another cable?

Ha! Connector tech is never that easy! It turns out that to make a perfect connection with Qi connectors, you need a special crimping tool. The Oscilloclock Lab does not have this tool. And we do NOT compromise on perfection! Given that this adapter is not the best reason to invest in an incredibly expensive tool, we decided to use the single pre-fitted cable and split out to two GPS connectors, with the larger one serving as the split point.

(In hindsight, we could have separately purchased another quality cable that was pre-fitted with the connector. Next time, folks!)

Wire up the cable

Our beloved ultra-quality Hirose connectors are a joy to look at, and a joy to use. But wiring the tiny smaller units up with high precision doesn’t exactly “spark joy”. Still, we persevere…

Now we need to install the 270 ohm series resistor. We simply cut the wire and splice it in.

A bit more heatshrink applied, and we’re done!

Closure at last

Using the 18x USB adapter, [Andrew] is at last able to upgrade his pucks and enjoy his clocks in their full glory with GPS-synchronized time and date once again!

Instructions for how to upgrade the software are posted on the Support – Garmin 18x page.

Did you enjoy this series? Stay tuned for more, as Oscillolife returns to nor….. Okay, not quite normal, but at least it returns!

Garmin “puck” USB adapter – Part 2

Posted on 2023/03/18 by Aaron

In the previous post, we looked at the Garmin 18x LVC “puck”. We talked about a particularly insidious issue that affected [Andrew] – both of his GPS units. And we saw that Oscilloclock owners really need to be able to update the firmware in these units.

We introduced the Oscilloclock Garmin 18x USB Adapter, that allows an Oscilloclock owner to connect their puck to a PC to enable the firmware upgrade.

In this post, we’ll take a look at the design of the Oscilloclock Garmin 18x USB Adapter. It wasn’t GPS satellite launcher (a.k.a. ‘rocket’) science, but it certainly wasn’t as straightforward as it might seem!

The Garmin 18x LVC electrical interface

Referencing the manual, the Garmin 18x series comes in 3 basic interface variations:

USB – USB 1.x interface, with a USB(-A) connector to plug into a PC
PC – RS-232 serial interface*, with a DB9 connector to plug into a PC, and a massive cigarette lighter adapter plug to obtain power
LVC – RS-232 serial interface*, with no connector – for wiring into a device

For our Oscilloclocks, we use the LVC variation and fit an attractive custom connector solution, avoiding the PC variation with its venerable, utilitarian, and aesthetically unpleasant DB-9 connector and cigarette lighter plug combo. (We may buck the trend one day and intentionally fit such sockets into that special retro clock build – who knows?!)

* Astute readers noticed the earlier asterisks. PC and LVC units are not quite true RS-232; their output voltage swings between 0V and +5V. Not so with devices having true RS-232 interfaces! A swing from -25V to +25V is legal and also lethal for any unsuspecting microcontroller. In the Oscilloclock design, we take advantage of Garmin’s voltage range cap to avoid having additional circuitry to adjust voltage levels.

Interfacing the 18x LVC to a PC

To upgrade the GPS firmware, the 18x LVC needs to connect nicely to a PC. But [Andrew] is an Oscilloclock Owner. He deserves more than just a good electrical connection. The interface also must be elegant and aesthetically pleasing, lightweight (for shipping), and easy to build. And – most of all – it has to be interesting enough to write a blog series about!

We can start with Figure 1 in the manual, which describes the most basic interface hook-up possible.

This interconnection option assumes two things: the PC has a DB-9 serial port, and there is a power source.

If we extend this option slightly, to take power from the PC’s USB port, we arrive at this:

Continue reading →

Longevity, and the Garmin “puck”

Posted on 2023/03/11 by Aaron

A few months ago, [Andrew] – of Metropolis Clock fame – reached out for help. He had just pulled his lovely Oscilloclocks out of storage to put on display, when he observed odd behaviour in both units: the time was accurate, but the date was stuck – to some random date back in 2003!

What on earth was going on?

What’s going on was not “on Earth” after all! [Andrew]’s clocks synchronise time and date against satellites, using an external Garmin GPS unit. And this unit happened to have a serious flaw. In this series of three articles, we’ll look closer at this accessory, identify this issue, and see how we were able to resolve it. Enjoy!

Our longevity dream

We want your Oscilloclock up and running as long as you are – and even beyond! Our dream is to see these beloved devices inherited by loved ones, and even available on the second-hand market as antiques one day.

In an era of throw-away technology, we flaunt an unthinkable target: Decades of trouble-free* operation.

* Excluding the CRT itself – although we really try hard with that as well, as this post explains!

To maximise usable lifetime (and safety!), we construct Oscilloclock units from the finest materials and components available. As part of this, we also select manufacturers that guarantee their components and provide decent after-sales support.

And Garmin is one such manufacturer…

Welcome to the Garmin GPS ‘Puck’

All Oscilloclock models that synchronise time using an external GPS unit have so far been supplied with a Garmin 18x LVC GPS unit, colloquially known as a ‘puck‘. (Note: to extend the lifetime of the pucks, we do not recommend using them on the hockey court.)

Now, this is not the smallest external GPS unit on the market today. But it has been available from Garmin since 2007, and is even being manufactured today! It is one of the most sensitive, robust, and well-supported units out there.

(Of course, for every new Oscilloclock delivered we evaluate afresh based on the latest devices available.)

This puck has a special connector …

How many times have you relegated an expensive laptop, phone, or other random device to the trash just because the power socket or headphone jack failed? Some of the weakest components of any electrical device are its connectors – plugs and sockets.

To combat such failures, your puck is wired with an exceptionally high quality connector from Hirose. This connectivity solution is not only robust, it even feels good! There’s a lovely audible and tactile ‘click’ when you engage the plug, and it locks securely in place. And unlike cheap chrome-plated connectors, we’ve proven that these babies do NOT corrode, even after a decade.

Toshiba ST-1248D Oscilloclock - GPS connector

-- We don't scrimp - we only crimp!

Continue reading →

Oscilloclock Bare(ly) makes it to Brazil

Posted on 2021/11/30 by Aaron

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?

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.

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

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New Year’s Resolution!

Posted on 2021/01/01 by Aaron

Q: “What’s your New Year’s Resolution?
A: “Why, 1024 x 768, of course!”

Geeky jokes aside, here at the Oscilloclock lab we DO have a form of New Year’s resolution! 「日進月歩」Nisshin-geppo, which loosely translates as “Steady progress day by day“, reflects the goal to complete the the once-in-a-decade re-design work, and resume crafting beautiful Oscilloclock products. It also highlights confidence that issues currently facing the wider world will be overcome, one step at a time.

In keeping with local traditions, [Oscilloboy] wrote the slogan in Japanese calligraphy. But there, tradition ended and true joy began! Behold, courtesy of an Oscilloclock VGA Core assembly, Oscilloclock’s 2021 New Year’s resolution on a beautiful old 7-inch oscilloscope!

The Setup

After choosing an appropriately meaningful four-character phrase for our resolution, I asked [Oscilloboy] to write out the characters. Bucking with tradition, we used standard white A4 paper instead of calligraphy paper. The ink took more time to dry, but we wanted to maximize the contrast.

[Oscilloboy] demonstrates his prowess in Japanese calligraphy. Right: the finished product!

After scanning the handwritten characters and inverting the images, I created a rolling video in 1024 x 768 resolution. (See? The joke at the beginning of the post about resolution was serious, after all!)

I then played this through an Oscilloclock VGA Core assembly, which is essentially a graphics card that allows you to use a beautiful old CRT as a rudimentary computer display. (For earlier write-ups, see VGA display… On a 3″ scope tube! and The VGA Cube! .

The assembly used here features a late prototype of the Revision 3 Power Board, which I have been working on for almost a year. I won’t go into all the bells & whistles yet. Stay tuned!

A VGA Core assembly – displays monochrome images from VGA, SVGA and XGA inputs

Unlike a permanent Oscilloclock conversion (see the Gallery for examples), this was only a temporary setup. The VGA Core was positioned externally, with the harness routed into the 7VP1(F) CRT via the rear of one of the side panels. No invasive procedures needed!

Just LOOK at that beautiful CRT socket – brown Bakelite!

No VGA socket on your ultramodern slim notebook of choice? No problem – use an off-the-shelf HDMI to VGA converter!

And voila – the final result! Japanese calligraphy on a vintage 7″ oscilloscope!

About the Model – A rare 1963 Nitsuki Oscilloscope

Nitsuki is the brand name of Japan Communication Equipment Co., Ltd., a specialist in television and microwave broadcasting systems. The firm’s English name was originally Nihon Tsushinki Co., Ltd., so you can see how the Nitsuki moniker came about.

Check out this exquisite cap on the pilot lamp!

By 1963, the Japan domestic test equipment market was mature and quite competitive. English language labeling had become stock-standard. This scope is one of very few units I have ever obtained that has Japanese labeling. How appropriate for today’s display!

Some of the higher-quality oscilloscopes of this era featured flip-latches and detachable side panels, for easy access. See the Toshiba ST-1248D for another example. These scopes are infinitely more enjoyable to work with and show off than scopes with a slide-out chassis.

This model is also quite unusual for its time in that most of the components are located under the chassis! The valves (tubes, if you prefer) are even mounted horizontally. Nitsuki used very robust construction techniques, including very tidy cable lacing.

In fact, their design was so robust that the scope functions almost perfectly today (except for some triggering instability), yet there is no evidence of major repairs in the last 57 years!

Back to its natural self – a nice old 7-inch 1963 oscilloscope!

Like what you see?

The Oscilloclock lab struggled in 2020 due to worldly events, but NOW – day by day, step by step, the newly designed Oscilloclock boards are at last taking shape! Does your New Year’s ‘resolution’ for your next project specify 1024 x 768? Or perhaps you’re into displaying fancy calligraphy on vintage CRTs? Let me know.

And as always, see previous posts and the Gallery for info on other unique creations!

Critical Update 25 December 2021

Well. Christmas Day 2021, and [Oscillowife] — the chief editor, advisor and critic extraordinaire — just informed me that I had placed [Oscilloboy]’s first character「日」upside down when creating this post! Apologies to our readers for the gross oversight.

It’s been **12 months**! But better late than never to eat humble pie…

New design on the way?

Posted on 2020/05/22 by oscillokid

Well, I think that’s what’s going on….

In a desperate attempt to save his blog from becoming the all too familiar not-updated-in-5-years dead blog, the senior technician has resorted to seeking help from one of his sons, previously referred to as the 1st junior technician. Although my knowledge on CRTs and electronics is close to none compared to that of the senior technician, I will give you some updates on the recent activities of the main man himself, who I am sure all of you are eagerly awaiting the return of.

Amid the COVID-19 crisis, the senior technician has been lucky enough to be able to work at home. You would think that without his everyday commute of two hours, he would be more relaxed and able to spend more time with his family members. However, he is instead spending excessive time in front of the computer. At first, I speculated that he was having a rough time with his work. Or was he? Under closer examination, I realized that the additional time spent on the PC was actually something related to Oscilloclock. Something about a brand new design: “once-in-a-decade refresh,” and some such. Not really sure how significant this is to you all, but judging from the look on his face when he emerges from his room for dinner, it must be something BIG!

Another clue that the Oscilloclock Lab is heavily active is the vast array of international deliveries to our home in the past half year. Shipments from countries that you’ve never heard of, in all shapes and sizes, arriving so frequently that I can’t help feeling for the poor postman who has to carry these heavy objects up to our door. I must tell you, there is nothing worse than hearing the bell ring and rushing down to the door anticipating your own Amazon delivery of a new pair of shoes, and instead seeing a massive box from Montenegro containing who-knows-what-type-of-CRT.

The master craftsman’s work could very well be hindered by the noise from his two highly energised teenagers, [Oscillokid] and [Oscilloboy]. So how does he maintain concentration? The secret is a well-positioned cave. His workshop is intentionally situated at the very edge of the house. He simply closes the lone door to the shop, to avoid hearing a dinner-call or a request for more screen time from his Oscillosons. Until, of course, the commander-in-chief of the household raises her voice!

So there it is, a brief update on what’s going on and how the senior technician’s doing. Rest assured that he is working very hard on his projects, and has not in the least swayed from his passion; indeed, he is more immersed than ever. He will no doubt inform all of you anxious readers of his magnificent projects once they are ready for exposure. Until then, thanks for reading, and stay safe!

Connect !!

Posted on 2019/04/30 by Aaron

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!