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
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.
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.
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!
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:
But who has a PC with a serial port in this day and age? Fortunately, there are plenty of RS232 Serial-to-USB converters out there – cheap and reliable! And we arrive at this:
Electrically, this is fine and dandy. And the build cost is not too bad. But it’s not so elegant. We can do so much more! First, we can get rid of the 2nd USB connector, by hacking into the serial-USB adapter, and tapping the power out from there:
While this solves the problem of the power, it’s NOT elegant, NOT pleasant to look at, and NOT really reliable.
Oscilloclock owners should not own junk, regardless of how ‘clever’ the solution is.
What we really want is an RS232 to USB adapter unit that provides both power and signal right out of the box. No hacking!
Sadly, there are no off the shelf RS232 to USB adapters that don’t have a DB9 socket embedded in them. We’d have to hack. Or, we could design our own elegant unit, from the PCB on up. (We’re good at that, but it would be a large effort to go to…)
A new idea – TTL Serial!
Is there another option? Well, in the past decade or two, TTL serial, another type of serial interface standard, has come into very common use. There are heaps of TTL serial to USB adapters on the market, and none of them have large clunky DB9 sockets built in!
It turns out the TTL serial electrical interface is similar to RS-232serial, with two differences:
TTL serial sports microcontroller-friendly voltage levels – i.e. between 0V and a capped upper limit such as 3.3V or 5V.
TTL serial uses intuitive signal polarity. A ‘low’ is represented by a low voltage, near 0V. In RS-232, however signals are inverted – ‘low’ is a +ve voltage, and ‘high’ is a -ve voltage.
On the first point, recall from an earlier footnote that the 18x LVC’s voltage swing is from 0 to supply voltage. This is actually in line with TTL serial. Nice!
But the second point is almost certainly why Garmin explicitly mention “RS-232 polarity” in the GPS 18x manual. They don’t want anyone using the 18x LVC to get it wrong:
Since the 18x LVC features RS-232 polarity signals, we design around this. For example, the Oscilloclock Control Board features inverters on the receive and transmit lines, to allow the microcontrollers to process the signals as if there were TTL serial:
Hey, wait a minute – if the 18x LVC is pretty much TTL serial compatible from a voltage standpoint, and it’s just a matter of signal inversion, then we could use one of many TTL serial to USB adapters on the market! Some of them look very pleasant indeed. We would just need to invert the signals. And thus we have the next design:
Doing just a little bit more research, it turns out that many of the common TTL serial to USB adapters on the market use a chip from FTDI, a company that specialises in USB bridging (interfacing) solutions. And the great news here is that FTDI chips support programmable inversion. We can eliminate the extra hardware needed to invert the signals!
FTDI provides a nifty app to program these inversion settings. We’ll see it in action soon.
CMOS vs TTL, and noisy signals
We noted earlier that the Garmin 18x LVC output swings between 0 and 5V. This is the same voltage range that TTL serial expects. All good, right? No, there is a slight difference that we may need to account for, to make the interface reliable.
The LVC has a CMOS output, while the FTDI chips have a TTL input. These acronyms describe the circuit configuration inside logic gates, and they differ in terms of the voltage ranges that logic gates deem acceptable when interpreting “low” vs. “high” signal levels.
There is an excellent writeup here that explains the difference in signal voltage levels in detail. The article explains that in an ideal world, connecting a CMOS output directly to a TTL input is not an issue. But our world is not ideal, and in our case we have a problem: TTL inputs are not very tolerant to noise compared to CMOS inputs.
And in reality, the LVC’s output signal is noisy! There are many possible factors:
The 5m-long cable may be lossy
The 5m-long cable may be picking up stray signals (like an antenna)
The LVC designers probably expected us to process signals with an RS232 interface or directly connect to a microcontroller – both having (less noise-sensitive) CMOS inputs
I’ll spare you an oscilloscope screenshot, but the concept is illustrated to the extreme in this figure. The actual voltage (in green) has AC noise superimposed, and is not even able to keep up with the small burst in the middle.
Probably the most serious ramification of this for us is that the voltage can actually exceed 5V. This is a big no-no for standard 5V TTL logic, where (unlike CMOS) the maximum input is a strict 5V. Behaviour is undefined or erratic above that level.
There are some impressive ways out there to solve this – for example, introducing a CMOS buffer right in front of the TTL gate. But our goal is to keep it simple yet reliable. How about a simple resistive voltage divider?
This reduces the risk of exceeding 5V by dropping the input voltage by about 20%. It also subdues stray signals picked up by the cable, by decreasing the input impedance.
One last improvement, anyone?
If we really want to go for aesthetics and elegance, we could tear apart the TTL serial to UBS adapter, and house it into a stunning custom case of our own design. And this would allow us to install a Hirose receptacle into the case, that the GPS can simply plug into directly! How cool would this be?
Unfortunately, this compromises our goal of making the solution easy to build and low in parts cost. After all, why design an adapter that costs almost as much as the actual GPS unit we’re trying to program?! So we’ll forgo this design.
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.
-- We don't scrimp - we only crimp!
A particularly insidious flaw!
No component or accessory of an Oscilloclock is perfectly future-proofed and completely immune to design flaws, software bugs, or unforeseen changes in global infrastructure.
The Garmin 18x is no exception, and there have been regular firmware updates through its lifetime so far, documented at Garmin’s Uploads & Downloads Page.
A particularly insidious issue occurred in 2019, when some older 18x devices could not handle the GPS Week Number Rollover, when a counter from the year 1980 reached its limit and reset to 0. (Remind anyone of Year 2000?)
This was the cause of the issue that [Andrew] observed!
This issue was particularly annoying because it affected only the date, not the time. An Oscilloclock owner could not turn off only the date synchronisation, so turning off the entire automated sync feature was the only way to be able to (manually) set a correct time.
But… How do you update the Garmin 18x?
In some cases, like [Andrew]’s, a puck really needs a firmware update. But some Oscilloclock owners just want to keep their gear up to date. How? There are two ways:
They can send the puck back to the Oscilloclock lab for a free upgrade. We only charge for the return shipping! But in these days of reduced shipping options, the journey can be pricy.
Owners can obtain an optional Oscilloclock Garmin 18x USB Adapter. Plug the puck into a PC, download the latest firmware, and update it themselves – whenever they wish! This is especially useful for [Andrew], who has more than one puck. (We just love folks who purchase multiple Oscilloclocks!)
Enter the Oscilloclock Garmin 18x USB Adapter
The Oscilloclock Garmin 18x USB Adapter consists of a specially-programmed USB-to-serial interface unit and a custom adaptor cable with a jack that matches the connector on the GPS puck.
If you have this adapter already and you’re looking for detailed usage instructions, let the Support -> Garmin 18x Puck page quench your thirst!
To be continued… In the next episode, wego through the design of the adapter!
Recent worldly events have taken a huge toll on the crafts and maker community globally. Sadly, the Oscilloclock Lab has not been immune.
It is with a heavy heart that I announce that Oscilloclock will be on official hiatus until further notice, at very least until the end of 2022. We won’t be accepting any further orders or enquiries, but any repair work for existing Oscilloclock patrons will continue to be handled with great passion and gusto.
This was a painful decision to make, but we are battling a perfect storm: extreme parts shortages, high shipping costs and long delays, a suddenly weakened yen (we are Japan-based), and an immediate need for your devoted cathode-ray engineer to focus on his day job and skills training as he reorganizes to go “back to office”.
I’m hopeful that in the coming 6-12 months, many of these factors will go back to ‘normal’, and we can formally resume our beloved cathode-ray activities! Stay subscribed to the site for future updates.
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] 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!
Clearly, [Dante]’s 18 month end-to-end was worth the wait.
[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!
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 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.
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.
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.
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!
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!
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.
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!
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!
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!
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.
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!
[Atif] is quite fond of his custom Oscilloclock Model 1, originally supplied with a bright green Brimar SE5F/P31 CRT. He just loves its crisp, clear trace! But wouldn’t it be great if he could plug-and-play a different CRT, to suit his mood of the day?
More specifically, could I create a second display unit (the acrylic tube on the left) using a CRT with a soft, long-persistence blue trace? And could he just swap the units around at will, without having to make any changes to the control unit?
Absolutely! But to make the 2nd unit completely compatible for plug-and-play, we’d need the same SE5F type CRT, with a different phosphor. Looking at Brimar’s catalogue, this CRT was available in several phosphors – including a P7 blue. This is the same as used in the original Prototype, and it’s really good at showing off those exotic trailing effects!
So the hunt began…
Now, this particular P7 CRT is famously difficult to come by – whether new OR used.
The most common piece of old equipment employing the SE5F was the ubiquitous Telequipment S51 oscilloscope, but the overwhelming majority of those had a P31 phosphor CRT installed. Indeed, of all the demonstrably working S51’s posted on eBay in the past decade, I have never seen a single one showing an obviously blue trace!
After many months of scouring auctions, suppliers and CRT fanatic colleagues across the globe, I managed to locate one SE5F/P7 in highly questionable condition – and located in Italy! With Google Translate as my friend, negotiations ensued, and – taking a substantial risk that the CRT would actually function – the unit was duly purchased and shipped.
Often, well-used CRTs exhibit scratches, spots, or burn-in marks on the internal phosphor coating. Fortunately, this CRT’s phosphor proved unblemished! And powering it up (for the first time in decades, most likely), it proved to be electrically faultless, as well!
Beautifying the Brimar
You may think that cleaning a CRT is hardly worth writing home (or the world) about.
But this specimen was slathered in sticky, gooey tape residue, which had to be carefully removed. My chemical of choice for this is, believe it or not, eucalyptus oil! Not only does it remove the gunk, but it also serves to clear up any nasal or bronchial congestion that the technician may have at the time. Two birds with one stone!
The more difficult issue was removal of the graphite coating. During manufacture, the front-most 8 cm of the glass of each SE5F was sprayed with a conductive graphite-based paint. Why? To make a high-voltage capacitor with the spiral accelerator anode (the beautiful green stripes) and similar graphite coating on the inside of the glass. By connecting the external coating to ground, the thrifty circuit designer could avoid using a separate (and expensive) high-voltage filter capacitor in the anode power supply!
Why remove this coating? Because during use, it gets scratched and marred, as the above photo shows. Such a messy CRT could never be worthy to mount in a clear cast-acrylic case for an Oscilloclock! In addition, the coating obscures some of the attractive spiral accelerator anode, and blocks the incredible view of the trace from behind. And regarding circuit design, we at Oscilloclock NEVER scrimp – the Power Board has oodles of filtering capacity without relying on a graphite coating!
While eucalyptus oil is also effective, it can get rather expensive in the quantity required – especially as the Oscilloclock lab is not conveniently located in Australia! The more reasonably priced chemical of choice here is nail polish remover. As always, there is a side-benefit – the nasal passages are assuaged by a delicate floral scent during cleaning, and fingers have an arguably nice smell that lingers for quite a while!
Joking aside – gloves, open windows, good ventilation, and safety glasses (in case the CRT implodes) are key ingredients for this process!
Having found the perfect CRT, [Atif]’s plug & play unit is now well under construction.
Epilogue – “Good things come in threes”
It’s not good just getting one CRT. What if [Atif] wanted a spare? What if I wanted a spare for my venerable Prototype clock? Following from the Italian success, I continued a further 6-month hunt, and managed two achievements.
The first was a Telequipment S51b unit located in the U.K. that was non-functional, but that I suspected may have a P7 phosphor installed. How could I possibly suspect this? Well, perhaps this is an art rather than a science, but there were several tell-tale signs:
The way the phosphor looked under the camera flash or ambient light
The colour (or absence) of the graticule (the plastic cover in front of the CRT)
The fact that I got a double when I rolled the dice to decide whether to take the plunge or not!
The seller of this unit was not willing (or perhaps not technically able) to extract the CRT, check the CRT type, or ship overseas. Fortunately, my colleague in the U.K. was more than happy to receive the scope at his end. Thus arranged, when the unit arrived he extracted the CRT and confirmed that – sadly – I had purchased a P31 CRT.
But I shipped it across anyway, and the CRT tested well. Rescuing a functional SE5F/P31 from eventual demise was still a worthy accomplishment!
The second achievement was prompted by an auction listing for a “Brimar SE5F”, but with little indication as to the phosphor. The photos of the label (see right), even with subsequent close-ups provided by the seller upon request, were not conclusive.
The image shows two characters beginning with ‘P’. It looks like “P1”, which is another extremely common green phosphor used in many CRTs since the beginning of time. However, we saw in the catalogue earlier that Brimar only supplied GV, P7, P31, and P39 phosphors as standard. It is unlikely that any equipment manufacturer would have requested Brimar to produce a custom CRT batch using the less-exotic P1 phosphor… Leaving the P7 as the only likely candidate!
Convinced, the CRT was duly shipped across and tested – and lo and behold, success! A spare P7 was safely procured.
And with that, the long saga of this CRT hunt closes. As they say, “good things come in threes!”
Like what you see?
Cathode ray tubes used to be manufactured in all shapes, sizes, and colours. Some prove harder than others to find! But if you prefer an exotic creation, don’t give up – there is something for you out there, and here at Oscilloclock we will find it.
As always, see previous posts and the Gallery for info on unique creations!
Recently I had an enquiry from [Frank], who had just begun a life-long love affair with scope clocks by purchasing one on eBay. The clock was great – but he felt that the two available screens (simple analogue and digital clock faces) lacked a certain oomph.
He then stumbled across Oscilloclock.com, and in his smitten state immediately reached out with his number one question: just what screens are available on an Oscilloclock?
Well, let me save Frank’s time trawling through years of blog posts. Right here in one place are most of the Oscilloclock screens and features created to date.
Enjoy the show!
Standard Time Screens
These stock-standard analogue and digital time screens may be quite simple, but they do evoke the ‘retro’ look that most people appreciate.
And you can flip a menu setting to display days, months, years in Japanese:
There are also some ‘random’ screens that add in a bit of dynamic visual entertainment:
Random number screen
Random letter sequence screen
Random four letter word screen (clean words only, by default!)
Random phrase screen (the phrase list is typically customized to a theme)
Over the years many folks have requested that I render custom logos in Circle Graphics. Here are some examples:
Up next are some fun, mildly interactive animation features. Not exactly screens per se, these animations pop up after a predefined period of inactivity – but only during certain months of the year. Can you guess which months?
There are far too many configuration menu and test screens to present here. Fiddle to your heart’s content!
Q. How are screens switched?
Screens are switched simply by rotating the control knob in one direction or other.
There is also a configurable auto-switch feature; the screen is changed every 90 seconds in a predefined order (with the exception of some animation screens). The display time is configurable, and the auto-switch feature can also be turned off for those who prefer to switch screens manually.
Q. How are screens selected & configured?
Customers can request screens to include and/or specify the switching order. The configuration is done here in the lab before clocks are delivered.
Oscilloclock also provides a firmware upgrade kit, which allows the customer to upload a revised version of the firmware into the clock themselves. Using this, updates to screens and other features can be uploaded without shipping the clock back to the lab.
Q. What is the process for rendering a custom screen or logo?
We typically prepare a mock-up based on the customer’s description, sketch, or image file. This is tweaked as needed until the screen looks just right to the customer.