[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!
Fake news – a common keyword these days. Fortunately, Oscilloclocks do not display fake news. But wouldn’t it be handy to see quake news on an exotic scope clock? This is the challenge [Atif] gave me – and one year and many grey hairs later, here is the result: The AfterShock Clock!
This custom-crafted Oscilloclock Core Duo assembly is a unique first in several ways:
It’s the first scope clock ever that pulls in and displays real earthquake data!
It’s the first scope clock ever that puts a dual-beam CRT to good use – one beam for the clock display, and the other for the earthquake and map overlay!
The AfterShock Clock’s WiFi module connects at regular intervals to two public APIs (servers) to collect the latest earthquake events. It then feeds earthquakes to the clock’s quake gun controller, rotating quakes every 30 seconds. Cool!
(Note: flickering is due to camera effects and is not visible to the human eye)
Of course, there is the usual wide variety of standard clock screens to cycle through! The quake map’s beam is automatically dimmed for most of the screens, giving a soft ‘watermark’ effect.
The E10-12GH CRT used in this clock is certainly not mundane!
Beautiful spiral PDA lets you really see inside the cavity!
Nothing beats a dual-gun CRT for intricacy… (except a quad- or pentuple-gun CRT!)
Oscilloclock Core Duo
Atif wanted to create his own case, so he initially asked for an Oscilloclock Core. But currently a single Core set does not provide control, deflection, and blanking circuits to drive TWO electron guns… So he had two choices:
Wait an eternity for me to redesign the boards to fully support dual beams.
Get started now! Simply put two Core assemblies together, with some degree of inter-control and removing any redundant circuits.
Atif chose the latter – and the Oscilloclock Core Duo was born!
Setting up the WiFi connection is easy – just connect a device to the clock’s administration SSID and pull up the admin page. (To foil any would-be hackers out there, the admin SSID is available only for the first 5 minutes after power is applied.)
Then, access the admin URL and configure the connection to your home router:
There are a million other advanced settings to tweak things such as quake polling interval, quake magnitude filters, maximum quake age before purge, and other geeky aspects….
Oh, I forgot to mention – the clock also synchronizes time against an NTP server, eliminating the need for a GPS module.
Like what you see?
Do you go for electron guns? idolize intricate electrode assemblies? Have a filament fetish? Or just want some quake news? This kind of clock might fit the bill. Let me know!
Many folks have asked whether screenburn-in, or phosphor burn, is not a problem. They are concerned by what was a frequent occurrence in the CRT monitors and oscilloscopes of yesteryear: a permanent scar prominently visible on the screen…
Phosphor burn – this old spectrum analyser looks ‘on’ even when it’s off!
To understand why this occurs, first think of an iron burn. If you deliver too much heat for too long into the same spot, your nice new Oscilloclock brand T-shirt will feature a prominent (and permanent) mark as shown below.
Iron burn – this shirt’s fibres have been literally scorched!
(I could push for another analogy, and describe livestock branding – but I think you get the message.)
In a CRT, a beam of fast-moving electrons bombards the phosphor coating on the screen to produce an image. If the beam is too intense, or it is allowed to trace the same route on the screen over a long period of time, the phosphor compound may degrade and lose its luminance. The end result is:
The screen won’t light up well in those spots any longer.
The damaged areas may appear dark even with the power off – a ‘ghost image’.
Interestingly, this damage does not actually shorten the working life of the CRT! (It does not affect the longevity of the heater, or the amount of gas permeating the vacuum.) However, it is certainly not attractive, and is most definitely NOT an effect you wish to observe on your fancy custom-crafted Oscilloclock…
Keeping the ghosts at bay
Happily, screen burn-in is not much a problem with the Oscilloclock. Let’s see why.
1. CRT selection
Some CRT types and brands are more susceptible to screen burn-in than others. There are a number of factors for this, and all of these are considered during CRT selection to minimize the risk of burn-in:
First, there is the phosphor compound used. Some phosphors, just by their chemical makeup, degrade faster than others. More significant, though, is the fact that some phosphors require more energy (electron beam intensity) to produce the same level of visible light output as others.
For example, a long-persistence blue P7 phosphor, such as used in the Model 1-S and the Prototype, is by its nature ‘darker’; it requires a higher beam intensity than the crisp green P1 or P31 phosphors used in many other models. The higher beam does make the P7 more vulnerable to burn-in.
Different phosphors need different intensities to appear ‘bright’ – so some will burn faster
Fortunately, the simple protection mechanisms in place in the Oscilloclock (we’ll get to these later) will avoid burn-in even on sensitive phosphors. The customer need not be concerned about this risk factor, and can select any of the available phosphors.
The second factor is the thickness of the phosphor coating. The thicker the phosphor, the less burn-in for the same beam intensity. Some CRTs are infamous for having ridiculously thin phosphor coatings, making them extremely susceptible to burn-in. Sadly, some CRTs that are most readily available today fall into this category, and their data sheets even specify an incredibly short maximum longevity of 1000 hours. That’s less than 2 months of continuous use!
Beware CRTs with short lifetime ratings – they may have ridiculously thin phosphors!
Most CRT manufacturers did not publish lifetime ratings, nor did they publish specifications of phosphor thickness. In the Oscilloclock lab, I rely mainly on my and others’ experiences with the manufacturer, and pick and choose only the highest-quality CRTs. Expensive – but definitely worth it!
The third factor is the use of any additional technology in the CRT that would allow for reduced beam intensities. The most common example is the aluminized screen, an additional coating on the rear of the phosphor. This coating reflects the light that would normally emanate from the phosphor towards the rear of the CRT, back into the phosphor (and the front of the screen). A much more efficient use of energy!
However, this technology was a later development, so many CRTs with an aluminized screen tend to be rectangular and have an in-built graticule. These may not be as visually pleasing in a standard Oscilloclock as non-aluminized CRTs.
2. Software (Firmware) protection mechanisms
Remember the phrase “screen saver”? In the pre-LCD monitor days, most computers employed some form of software that would stop the same image being displayed for too long, to avoid screen burn-in.
My favourite screensaver – Flying Toasters! (Image used under Fair Use terms)
While there is nothing as fancy as flying toasters, the Oscilloclock has several mechanisms in place.
Hourly XY Bump screen saver
This feature simply shifts the image by a small amount in the X and Y directions every hour. The shift pattern repeats every 31 hours (a prime number), to ensure that every hour numeral will be placed in every screen position.
Auto screen switch
This feature simply cycles through the screens (clock faces) at regular intervals, configurable from 0 (off) to 90 seconds. This is by far the most commonly enabled feature, as it allows one to enjoy all the Oscilloclock screens without touching the control!
Auto power off
Strongly recommended by Oscilloclock labs, this feature simply turns the Oscilloclock off after a period of non-activity (not touching the control), configurable from 0 (off) to 90 minutes.
This may sound counter-intuitive, but in practice, nearly all Oscilloclock owners are comfortable to turn their unit on just when they intend to enjoy it, and allow it to switch itself off. The exceptions are clocks that are permanent fixtures in offices and restaurants, in which case the owners manually turn their clocks on and off together with other appliances in the premises.
These features are of course highlighted in the Operation Guide that accompanies every Oscilloclock.
Summing it up
So there we have it – there’s not so much to be concerned about after all. While CRTs do have a delicate phosphor coating, by selecting a decent CRT in the first place and looking after it in use, the risk of screen burn-in is drastically reduced. In fact, in 7 years of constructing Oscilloclocks, as of today not a single unit has come back for a CRT replacement!
Time – the universal constant. Time passes the same for all peoples; rich or poor, busy or idle, inspired or dispirited. And time has certainly passed for Oscilloclock.com since the 2015 Tokyo Maker Faire – the event that just keeps giving!
At last, we present the final model from that Faire – the Kikusui 537 Oscilloclock!
The Kikusui 537 was hand-picked for conversion by the lab’s youngest technician (9 at the time). He chose it for its small size and portability, but also for its cute colour scheme! A dainty red sweep adjustment knob highlights a bright white and black control panel, with a blue case providing overall contrast and visual soothing.
The 537 Oscilloclock’s small size makes it the perfect clock for an office desk, bedside table, or mantle. And since this is a ‘maximum re-use’ conversion, the existing circuit is active and all the front panel controls are fully functional. Fiddle with the image’s size and position to your heart’s content! Switch from XY mode to normal sweep mode, to view raw Oscilloclock signals in real time, as the seconds tick by!
The 537 was manufactured by Kikusui Electronics Corp., a major producer of test equipment in Japan since 1951. It was produced in large numbers from 1975 and was extremely popular for its small form factor, solid-state design, 5 MHz bandwidth, and ‘low’ price of 45,000 yen (perhaps USD 1,000 in today’s terms). See the catalogue page (Japanese only) and the operating manual (Japanese and English).
The Kikusui Electronics Corp. logo
In a previous post, I mentioned there are several general approaches to converting an oscilloscope. Since the Kikusui 537 is fully solid-state (it uses transistors instead of valves/tubes, except for the CRT) and it is only 40 years old, I decided on the maximum re-use, minimal invasion approach. (I really should trademark that term!)
This approach involves tying the Oscilloclock Control Board‘s outputs directly into the existing X and Y amplifier circuits. This was easy to do in the 537!
Oscilloclock Control Board mounted in the 537
However, as discussed in the Circle Graphics post, we also need to be able to blank the beam at extremely precise intervals. Sadly, the 537 (like nearly all oscilloscopes of this vintage) does NOT have a convenient DC pulse-tolerant Z-axis input. I therefore installed an Oscilloclock Power Board, partially populated to serve as an isolated blanking amplifier, in series with the grid.
Partially populated Oscilloclock Power Board
Finally, an Oscilloclock Supply Board was needed to power the other boards.
An Oscilloclock Supply Board is also nestled in there!
Mounting the Control
What better place to fit the rotary encoder, than on the beautiful red sweep frequency adjustment knob that my junior technician liked so much! Here’s the general story:
Sweep adjust control in its original state
After removing the potentiometer
The encoder, after hacking with a hacksaw!
Voila – sweep knob now drives the rotary encoder!
Like what you see?
One of the two Kikusui 537 Oscilloclocks crafted for the Maker Faire is still available for the special person with a soft spot for a krazy kikusui klock. Visit the Availability page for more information, and of course see the Gallery for other unique creations!
Over the years, folks out there have reached out to me with all sorts of crazy ideas about cases and housings for scope clocks and custom CRT displays. Here are some interesting examples:
The console of a vintage pipe organ
An ancient grandfather clock
A cylindrical case made of some exotic wood
A “cathedral” style vintage radio
Essentially, these people wanted just the innards of an Oscilloclock, which they would build into their own case. Could I help out?
Absolutely! For people who want to roll their own cases, and who have experience handling high voltage electronics and CRTs, I occasionally prepare custom board sets that are lovingly hand-assembled, tested, and tweaked for optimum performance with a given CRT. Here we go:
The Oscilloclock Core
An Oscilloclock Core, hand-crafted in 2015 for a discerning customer in Germany
The standard Oscilloclock Core layout, on a test acrylic mounting
I supplied this particular unit with an 8SJ42J Chinese-made CRT, just for testing purposes. This is a 3″ PDA tube with a highly restrictive rectangular viewing area, but the customer found it just great for checking things out!
What comes with it?
Here’s what’s comprises the typical Oscilloclock Core:
1 x Fully assembled and programmed Control Board (optional on-board GPS)
1 x Fully assembled Deflection Board (latest ultra-linear revision)
1 x Fully assembled Power Board optimised for a given CRT (latest revision with options: onboard high-bandwidth blanking amplifier, rotation coil supply, auto fan speed control, unblanking plate modulation, and isolated bright/dim input)
1 x Fully assembled CRT Board (optional; an external blanking amplifier recommended when the CRT cable is longer than 50cm)
1 x Rotary encoder
1 x Worldwide 9V power supply (high quality wall wort unit, commercial ratings)
1 x Garmin GPS unit with 5m cable; wired to board-side connector (not required for onboard GPS)
1 x Set of standard inter-board and CRT harnesses for testing and reference (10kV/3kV silicone melt-proof used for HV cables, other LV cabling also heat-resistant)
1 x Cast acrylic test mounting assembly, fitted with the boards, ready for testing out-of-the-box with your CRT
1 x Ceramic adjustment screwdriver
Service documentation (schematics, board layouts, complete Digikey BOMs, harness specs)
All components are latest available types sourced within the last 6 months, 0.1% or 1% tolerance resistors, minimum 2 x rated working voltage capacitors, all lovingly hand-mounted by myself
All boards sprayed with HV lacquer for moisture and arcing protection
2-week satisfaction guarantee. But no long-term warranty on board-only purchases
Naturally, the lengths of all harnesses and inter-board cabling can be customized according to the owner’s requirements. And there is also an Oscilloclock Core Cube arrangement, where the boards are stacked to reduce the length and width of the overall unit.
What CRTs does it support?
The Power Board and Deflection Board are increasingly flexible with each revision, but I insist on performing all configuration of the Core here in my lab. This allows me to tweak for maximum performance, and provide a proper satisfaction guarantee.
Typically I work with the owner to recommend a CRT based on preferences such as size, colour, and aesthetics. However in cases where the owner already has a CRT in mind, and I don’t have the particular CRT or a close equivalent, I ask the owner to send me one to test against. Or, I simply procure one; after all, one can never have too many CRTs! (Though my better half does not agree…)
The current Oscilloclock Core board revisions meet the following operating parameters:
Maximum cathode to deflection voltage of 2175V
Maximum accelerator voltage of 3525V for PDA type CRTs
6.3V heater, max 0.7A
Support for “Deflection Blanking” CRTs (see treatise here)
CRT rotation coil supply (+/-5V)
Precision deflection amplifier capable of driving +/- 275V with 0.1% linearity
Like what you see?
Check out the Availability page for more information, and of course see the Gallery for some unique CRT creations – many with an Oscilloclock Core at their heart!
Fresh off the press – some photos of the Oscilloblock – Summer Dusk edition in its new home! The owner is clearly a huge Nixie tube and neon aficionado, but this is his very first CRT clock. What a fitting environment!
Fortunately, I didn’t need to guess any further. As I was once an avid flight simulator enthusiast, I quickly hit upon the correct meaning: Head-Up Display. This is a mechanism that overlays instrumentation or map data onto the view looking forward from the cockpit, so that the pilot doesn’t have to look down to see this information.
Wikipedia has a great introduction to HUDs and their history, but Mike’s Flight Deck has the definitive tome for flight simulator enthusiasts who want to actually build an HUD. According to Mike, the system employs various optical paraphernalia, but at the heart of the mechanism is what lies closest to my own heart – a CRT Display!
An Oscilloclock 3-inch X-Y-Z display unit, optimized for use in an HUD
Humpty Dumpty sat on a wall…
Humpty Dumpty had a great fall…
…and so the great nursery rhyme goes! But here at Oscilloclock labs, we’re not talking about an egg (which, one theory goes, represented the defeated King Richard III). We’re talking about a beautiful old CRT, savagely shaken and shattered during international shipping. What a waste. But oh, what a great chance to see the insides close-up!
This broken CRT missed its chance to live again in a nice VectorClock
Looking down the barrel. Imagine you are a phosphor molecule, with projectiles from this gun hitting you at the speed of light!
Fresh from Oscilloclock Labs – a new VectorClock creation, commissioned for the office of a world-famous film and television director:
Tek 520 VectorClock – S/N 002 (image published with permission of the owner)
This unit is based on an original Tektronix 520 vectorscope, which is the predecessor of the 520A that was used in the first VectorClock, described here. This custom conversion employs several key enhancements, and performance has never been better!