Next time we craft up a CRT harness, we’ll snap a few photos along the way. It’s a surprisingly deep topic!
The opportunity came in April, when [Nick] commissioned an Oscilloclock Exo as a birthday gift for his father. What a thoughtful son; what a lucky dad!
So – time to get the camera out and take those promised shots!
Custom crafted cabling for an Exo 3KP1. This harness just begs to be connected…
The Harvest
Spring. Such a lovely time of year! Birds sing, bees buzz, and the bottomless bellies of big auction houses swell as people go about their spring cleaning, throwing out their clutter of yesteryear.
Spring is harvest time. Vintage valve test equipment bounty for salvaging, scavenging, and scraping. And we hate to see a scrapping…
… which is how a key part for [Nick’s] dad’s Exo’s CRT harness was obtained!
Sad, lonely, and forlorn – how could we help but rescue it?
That’s right. Every Oscilloclock Exo harness incorporates an original brown bakelite CRT socket, specially harvested from rescued equipment.
A harvested CRT socket, with rear cap removed
After a CRT socket is harvested, all existing wires are desoldered, and the socket is cleaned thoroughly to remove all traces of residue. We even polish the bakelite, to bring out a beautiful grainy texture and lustre!
What Wire?
Voltage, voltage, and more voltage. The more the better, for a bright and sharp image – to the limit of the CRT’s specifications, of course!
[Nick’s] dad’s Exo’s CRT would be driven by a potential difference of 2,000 volts. Given time, the insulation in standard hookup wire would be punctured through at this voltage, resulting in arcing or even worse: fire or electric shock.
We don’t take chances! Oscilloclock CRT harnesses are made from silicone wire, rated at 3,000 volts and 150°C. Remember we talked about longevity? We weren’t joking – this wire weathers whatever, forever!
Stripped & Secured
Measuring and cutting is great fun! We all learned this in pre-school. But the essential skill of stripping wire comes much later in one’s life.
It’s a delicate operation. Strip too much, and stray strands could short-circuit. Strip too little, and the solder joint may not be secure.
In the Oscilloclock lab, almost everything is done by hand. But we pride ourselves on using the correct equipment, where it matters!
A genuine Molex. Expense is no object, when it comes to strip lengths!
After stripping comes soldering. This skill can literally be studied and improved upon for years, given the varieties of solder, flux, irons, and application techniques out there. At Oscilloclock, your lead engineer (and author…) has been soldering since the age of six, taught by Grandpa…
Lab-quality equipment also plays a key role in reducing dreaded ‘dry joints’.
Grandpa’s book – food for the soul!A soldering station helps keep things hot…
After soldering, we slip on heatshrink tubing – this protects the naked terminals from dust. It also minimizes the potential for arcing across the air gap, especially in a high-humidity environment.
All soldered and heatshrunk!
The 3 E’s: experience, expertise, and expense. All to keep [Nick’s] dad safe from the dangers of a loose wire floating around at 2,000 volts!
Shall we Shield?
Yes! In [Nick’s] dad’s Exo design, there are a few wires that carry AC signals. Even worse, they carry high-frequency pulses.
Remember the days of analog television and radio, when you brought a modern electronic device such as a computer or a phone close to the antenna? You saw (or heard) electromagnetic interference (EMI). Snow, buzz, hiss – this was all because the offending device was transmitting a signal!
We won’t go into theory here, but yes – we do want to shield these wires.
Shielding applied to three wires, to avoid interference and crosstalk…
Finally we’re ready to apply the external sheath. This is made from a braided material to provide strength yet flexibility. And it looks great!
We also slip on a specially designed rear cap (backplate), which has been custom-machined from black acrylic. This keeps dust, prying fingers, noses, or snouts out of the terminals. Nylon spacers safely insulate the screws (stainless steel, of course!) from the terminals.
French Connection
What image does “France” evoke for you: Romance? Fashion? Food?
For us, it’s connectors! With its leading presence in the aerospace, space, and military industries, French engineers have created connection technologies that rival all others in handling severe environments.
And we need a good connector for the other end of [Nick’s] dad’s harness. One that handles high voltages. One that’s fashionable. Romantic. Delicious, even! And France1 delivers it all:
Exotic connectors, with variations from the basic to the ridiculously luxurious!
The company in question has since been acquired by a U.S. corporation. But we still classify the system as “French” due to its origins. And because it sounds good! ↩︎
Critical Crimping
Oscilloclock owners choose their preferred level of decadance. This even applies to the pins used in the connection system!
Gold or tin – what is your preference?
But whether they select the extravagantly gold-plated, or just the basic tin, we need to affix the wires to the pins in the most reliable possibly way. We need to crimp!
Crimping is the process of squeezing the metal tabs at the rear end of the pin around the strands of the wire, making an incredibly strong and low-resistance connection. The science behind this is amazing, and is worth its own article! For now, take our word for it – never solder when you can crimp.
And as usual, we don’t scrimp on the crimp. [Nick’s] dad deserves the best:
Extravagance beyond bounds. We love this aerospace-quality crimp tool!
Finishing touches
At last! The harness is looking like a harness.
At the final stage, we insert the pins into the plug, apply a specially grippy heatshrink onto the Oscilloclock end of the cable, and insert a small strip of silicone rubber prior to tightening the cable stay.
And voila!
Both ends of [Nick’s] dad’s Exo’s harness turned out beautifully!
Like what you see?
We love to harvest, harness, and handcraft. If you have exotic cabling requirements for your dream Oscilloclock, or indeed any custom cathode-ray tube connection system, it would be a delight to discuss! Contact us.
It’s a sobering thought, and not a particularly pleasant one, that your Oscilloclock might just outlive you…
But let’s not dwell on such talk! The real focus today is the oft-asked question: “How long will my Oscilloclock last?”
The honest answer is: we don’t know.
However, we do know how we try to maximize longevity, and we do have repair and return statistics from 15 years of delivering beautiful Oscilloclocks. We’ll go through all of this with you!
Your Oscilloclock
There are many different models and styles of Oscilloclocks (see the Gallery), with infinite variations in terms of parts that make up the final product.
But in terms of longevity, we can broadly categorize components like this:
CRT – the cathode-ray tube display
Hardware – the case, mounting supports, thermal parts, nuts and bolts
Oscilloclock boards – the electronics designed and built right here in the Oscilloclock lab
Original device circuitry – the host device’s original electronics that are kept in use (if any)
Harnesses and cabling – wires, plugs and sockets; both internal and external
In today’s post, we’ll tackle the proverbial elephant in the room – the CRT!
Your CRT
Your clock’s cathode-ray tube is actually a type of vacuum tube. There is a glass enclosure, with a screen coated with chemical phosphor. It has a heater (or filament), and other electrodes made of special materials. These are welded to wires that are soldered to pins protruding through airtight seals in the glass.
Each italicized word adds up to this: A CRT is quite fragile!
The CRT – easily the most delicate part of any Oscilloclock!
CRTs have many “failure modes” – and we’ve seen them all! Let’s explore.
Failure mode A: Natural causes
Vacuum tubes (or valves) rely on thermionic emission. Electrons are emitted from one of the electrodes called the cathode, when it is heated up and voltage is applied.
In a CRT, thermionic emission is used to create the all-important electron beam
In any vacuum tube, this emission capability decreases over long periods of active use. This is most commonly due to a degradation of the special emissive material and coatings that are used in the cathode.
Your Oscilloclock’s beautiful CRT will face the same issue eventually. As the number of electrons bombarding the phosphor screen decreases, the image will gradually get dimmer and dimmer, until eventually it cannot be seen.
How long will a new, unused CRT last before it succumbs? Well, manufacturers quote working lifespans of tens of thousands of hours of active use (heated and voltage applied). This equates to a few years.
We want our Oscilloclock CRTs to last decades, not years! So what do we do?
Secret 1: 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). Alternatively, owners can set a specific “Off at:” time.
It may sound counter-intuitive, but in practice, all Oscilloclock owners to date have been comfortable to turn their unit on just when they intend to enjoy it, and allow it to switch itself off.
For clocks that are permanent fixtures in offices and restaurants, staff manually turn their clocks on together with other appliances in the premises, and set them to turn off at the business closing time.
Secret 2: CRT type and manufacturer selection
While working with the owner to choose their CRT, we emphatically avoid tubes where the manufacturer quotes short lifetime ratings.
Sadly, some CRTs that are most readily available today fall into this category. See the data sheet below, specifying an incredibly short maximum longevity of just thousands of hours!
Q. What can be done for a CRT ‘on its last legs’?
Sadly, it isn’t feasible to restore a dead CRT to factory condition. But there are two things that can be done before it reaches that state, to prolong the inevitable:
Firstly, Oscilloclock owners can adjust the Intensity control, as described in the Operation Guide. This will drive the CRT harder and brighten the image.
Secondly, here in the Oscilloclock lab, we can attempt a CRT rejuvenation. This procedure involves carefully applying higher-than-normal voltages to the heater, and between certain electrodes. Done correctly, this can ‘peel back’ a thin layer of the cathode surface that has degraded or suffered from ‘cathode poisoning’, to reveal a more emissive layer of material beneath.
Q. Will a new (unused) CRT last longer than a used one?
Theoretically, yes.
BUT in all our experience at Oscilloclock.com, we see no evidence that new-old-stock CRTs last any longer than used ones.
Why is that? Well, most CRTs we use are harvested from laboratory test equipment. Most operators typically switch lab equipment on only when needed – so the accumulated operating time is often very short.
In fact, we openly encourage the owners to choose a pre-loved tube! We vet all our CRTs, testing them electrically and inspecting for any damage to heater, phosphor, glassware, or seals. No electrode is unturned; no emission-impacting detail is omitted!
Failure mode B: Humpty Dumpty
Humpty Dumpty sat on a wall… Humpty Dumpty had a great fall…
If the CRT glass is cracked or broken, there will be rapid loss of vacuum inside, halting all electron emission. If voltage is applied, the heater will quickly burn out, due to oxidation.
All the king’s horses and all the king’s men, Couldn’t put Humpty together again.
Sadly, several CRTs have arrived at our lab in this woeful state.
Secret 3: Shipping precautions
We take great pains to ensure that Oscilloclock owners do not experience a Humpty Dumpty episode.
CRT mounting – in all Oscilloclock models we ensure the CRT is mounted with sufficient cushioning (silicon or rubber) against its mechanical supports.
Double-boxing – all separable components of an Oscilloclock are individually boxed prior to packing into a larger box for shipping.
Packing material – we use a combination of bubble wrap, foam peas, and Styrofoam to cushion the internal boxes and their contents.
Box selection – we love to recycle, and we have loads of used boxes on hand. We pick the stronger ones and make sure they are the right size – large enough to fit cushioning material, but never so large that the inner boxes might slide around!
Carrier – we have had extremely good results with the standard EMS service available from Japan Post, and this is what we always recommend.
Insurance – we always insure the shipment to a sufficient value.
Thanks to this secret, to date we have only had one case of breakage for an item shipped out from our lab! And even then, the insurance claims process working with Japan Post was quite straightforward – if not even pleasant.
Failure mode C: Gassy CRT
No, CRTs can’t eat too many potatoes! But CRTs definitely do not like air.
A CRT may become “gassy” if too much air leaks in via the pin seals or a fracture in the glass, such that its internal self-healing mechanism (formed by the getter electrode) is overwhelmed.
This CRT is gassy, as indicated by white precipitate near the “getter”
On a gassy CRT, the image will become dimmer and dimmer until it disappears entirely.
While there is no true remedy for this malaise, an owner can postpone the inevitable by adjusting the Intensity control. And in rare cases, the CRT rejuvenation procedure described earlier may stimulate the getter electrode to mop up some of the excess gas.
Secret 4: Avoid potatoes mechanical shock
Gassy CRTs crop up occasionally, usually as a result of excessive mechanical stress or shock.
Besides shipping precautions (Secret 4), we are even careful when storing CRTs. Being situated in the Japanese archipelago, the Oscilloclock lab and all its contents must endure significant earthquakes occasionally.
We therefore place the most precious CRTs in strongholds – small cavities in the woodwork that suffer less shaking and are very unlikely to collapse (even if the rest of the lab does). Touch wood!
Our miniature lab securely houses more than 130 rare CRTs…… but where?
Failure mode D: Phosphor burn
Roughly 10% of the CRTs we harvest exhibit a permanent scar, prominently visible to the naked eye…
Phosphor burn – it 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!
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 result:
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’.
Devastatingly, it just isn’t possible to restore the phosphor. But since these CRTs are otherwise perfectly healthy, we put them to good use in the lab for testing and experiments.
Secret 5: Choose a decent CRT
Some CRT types and brands are more susceptible to screen burn-in than others. Some factors include:
The factory list price (you do get what you pay for)
The manufacturer’s credit rating for reliability
The phosphor compound used
The thickness of the phosphor coating
Any additional technology; e.g. aluminized screens
For more details, see our deep-dive post: Burn-in? Nope!
Secret 6: Screen-savers and other 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.
In addition to Secret 1 (Auto power off), Oscilloclocks have several more screen-saving features that protect the phosphor:
Hourly XY Bump – shifts the image by a small amount in the X and Y directions every hour
Auto screen switch – cycles through the screens (clock faces) at regular intervals
Bright/dim control – switches between preset beam intensities via a front-panel control (on some models)
Intensity control – manually adjust beam intensity if required to suit darker rooms
For more details, see our deep-dive post: Burn-in? Nope!
Failure mode E: Disconnected electrode
Very rarely, the weld between an electrode and its connecting wire fails. Or the soldered joint between the wire and the external pin fails.
The symptoms depend on which electrode has been disconnected, but one thing is for sure: the CRT becomes defunct. How awfully sad.
This cutie is perfectly healthy.. Except, it can’t focus. See the weld failure at right ..
Secret 7: Cry and move on…
I would like to simply write, “Choose a reliable manufacturer.” However, they don’t get much more reliable than Tektronix!
Besides protecting the CRT from mechanical shock (see previous Secrets), all we can do is accept fate…
Failure mode F: Open heater
A CRT heater (filament), just visible
Remember incandescent light bulbs of yore, with a delicate filament wire suspended inside the glass? They burned out over time – typically with a break in the wire that you could even see with the naked eye!
Well, the heater in a CRT is also formed from filament wire (albeit with different metals designed to emit more heat than light). If a CRT heater burns out, the cathode cannot be heated sufficiently to emit electrons, and the tube is rendered useless. A sad, sad state of affairs…
But what causes such failure?
Well, when did light bulbs typically fail? Yes! Right when you switched them on!
The reason is that a cold filament has a very low resistance. When you apply voltage, a huge amount of current flows (called inrush current). This settles as the heater warms, but the initial power and sudden temperature change causes metal fatigue. And after many switch-on cycles, the wire can break.
Secret 8: Soft-start!
The best way to preserve the heater is to limit the inrush current, so that the filament can warm up gradually. Every Oscilloclock employs one of the following 3 types of inrush current limiter:
1. The sacrificial lamb – a light bulb!
In this scheme, we simply place a specially-selected incandescent light bulb in series with the CRT heater. Upon switch-on, most of the supply voltage is applied to the light bulb’s filament (because the CRT heater’s resistance is low), making it light up brightly.
Primitive. Low-cost. Yet immensely effective!
As the CRT heater gradually warms up, its resistance increases. The voltage across the light bulb decreases, making it dim and cool down, and its resistance lowers. By this time, the CRT has fully warmed up and stabilized, with most of the voltage now shifted to the CRT heater.
Functional, AND beautiful to watch! Besides the Exo in the video, we’ve used it in the Heathkit OR-1 Oscilloclock and a few other custom pieces.
2. Mister thermistor
These long-legged beauties are called thermistors. They have an odd characteristic called NTC (negative-temperature-coefficient). The hotter they get, the less their resistance!
Does that sound familiar? Yes! They can replace the light bulb used in method (1) above. Most of our Oscilloclocks employ these devices, because they are reliable, predictable, and very small.
Nonetheless, we enjoy the switch-on supernova of the old-fashioned light bulb. And some owners do, too!
3. Electronic soft start
Both light bulbs and thermistors are passive devices; their resistance vs. temperature profile is known (and can be charted in a specifications sheet). BUT they are not aware. They don’t have any kind of feedback loop, so they don’t actively control the voltage across the CRT.
Recent Oscilloclock Power Board designs provide an active soft-start option. This is a circuit that dynamically ramps the output voltage up from 0V to the final voltage in a preconfigured number of seconds.
Effective and reliable, but just a little more complex!
Q. Will running the heater at a lower voltage prolong the CRT?
No. According to many folks, running filaments at lower voltages than specified can accelerate “cathode poisoning” – degradation of the cathode material due to absorption or chemical reaction with trace foreign substances. We don’t recommend this.
Yes, eventually. However, it will certainly outlast the CRT filament. Although the light bulb filament does suffer a high inrush current, even a cold CRT presents a small resistance into the circuit. The voltage across the bulb at turn-on is therefore less than its rated voltage, and this extends its life.
Q. Isn’t there something that can be done to restore a CRT heater?
Maybe. Some folks have managed to ‘fuse’ a broken heater together, by injecting a very high voltage (thousands of volts) across the gap. The resulting arc effectively welds the broken filament. We haven’t yet had the pleasure of trying this, but if we do we will certainly write it up for you!
Replacing the CRT
Fact: In 15 years of crafting Oscilloclocks, not a single unit has ever come back for CRT replacement!
That said, every CRT we shipped will reach its end of life. It’s just a matter of time.
But don’t despair! Oscilloclock carries spares for most common tubes, and we can supply and replace them. Some owners even choose to purchase spare CRTs with their original order, so that they have them on hand.
Q. What about rare CRTs?
If a clock was crafted from a particularly rare CRT, there may be no spare available. But again – do not despair! We can work with the owner to select another type of CRT, and modify their precious device to suit. By rejuvenating their clock ‘with a twist’, the owner may experience even more of a thrill than if we simply restored it to its previous state!
A rare CRT: type D4P. Don’t worry – we can replace it with something!
Q. Can owners replace the CRT by themselves?
We always recommend shipping clocks back to the lab for CRT replacement.
However some models, especially those in the Oscilloclock Exo series, employ a simple and safe mechanism to swap CRTs – and we provide instructions in the Operation Guide for doing this.
Q. Does Oscilloclock.com produce or repair CRTs?
No. We dream of one day establishing a CRT factory. Or at least a CRT repair facility. However with all the toxic chemicals, high vacuum, glasswork, and intricate welding involved, this is likely to remain a dream.
Q. Are new CRTs being manufactured anywhere in the world?
Yes – some types of CRTs are being manufactured in some countries. However many are not suitable for Oscilloclocks. They may employ electromagnetic deflection (which we don’t yet support), they are special-purpose for military or aerospace applications (too expensive!), they are very cheaply-produced (not reliable), or they have short lifetimes per design and require frequent replacement.
Swappable CRTs!
Many of our ‘Full Package’ type clocks (see Gallery) support display swapping.
Essentially, we craft complete additional display units, which the owner can swap in at will simply by swapping cables to the Control Unit. There is no need to open a case, touch the CRT itself, or any form of delicate operation.
This is normally used to change the ‘mood’ of an Oscilloclock, by swapping in different phosphor colors. But it also can be used to more easily swap in a replacement CRT.
Do you want long life, both for yourself and for your precious electronic devices? Are you tired of modern society’s throwaway culture, built-in obsolescence, and device non-serviceability? Our goal: electronic artwork that might be passed down a generation (or more) in actual working order!
Stay tuned for Secrets Parte II, where we will explore the life of other components!
Recently, [Justin] asked: Can his beautiful Tektronix 606 XY monitor be made to work as a computer display?
And even more recently, [TJ] explained he has a plethora of Tektronix devices, and asked how he might put them to use…
So lovely… but what can you DO with it?
Well, “putting to use” is precisely what we do here at Oscilloclock! And one option, indeed, is to hook the target device up to a modern-day PC and use it as a computer monitor.
Time for an update on the Oscilloclock VGA Core and its variants!
Shades of Grey Green
Avid readers may recall these previous posts about making SVGA and XVGA displays from vintage oscilloscope CRTs:
Truly dedicated readers may even recall that the solutions presented drive the CRT directly, completely bypassing any internal circuitry of the host device. And, that there were limitations in the current design; the most serious being binary blanking, where the beam is switched either on or off. There were no shades of grey.
This Running Man needs no shades!
Inspired by [Justin], we experimented connecting the Oscilloclock VGA Bare (a barebones VGA interface board) to our lab’s Tektronix 620 XY monitor. This bad boy has an analog Z axis (intensity) input, meaning that we can theoretically have shades of grey… er, green.
And the result? A pretty decent PC display!
A recent post, as displayed on the Tektronix 620. (Yes – I know it’s upside down)Here’s what it looked like on the laptop’s display
Doomy Demo
Ever wanted to play classic Doom on an old green screen? Here we go!
This Tek 620 is no longer doomed – it’s been Doomed!
Yes – the display is horizontally inverted. The VGA Bare currently does not support flipping the X and Y signals.
This unintended challenge makes playing Doom exceptionally difficult!
Matrix Masterpiece
Who could resist displaying digital rain (Matrix code) on an old Tek display?
Matrix code, as generated by tmatrix. Note it’s horizontally inverted
While working on this demo, I learned more about Matrix code – and that it includes Japanese characters scanned from the creator’s wife’s cookbook. Wow, I thought those raindrops looked awfully familiar!
The Setup
Not a bad result! And the hardware setup was simple.
PC
HDMI to VGA adapter cable
Oscilloclock VGA Bare
BNC cables and connectors
A few resistors
Power pack
As always, nothing is perfect! A few tricks were needed to make the experiment a success:
The VGA Bare circuit needed a few minor improvements, to better support official SVGA and XVGA timing standards
A crude level adjuster (resistive divider network) was needed between the analog intensity output and the Tek’s Z axis input
The PC display resolution needed to be set to SVGA (800 x 600) or XVGA (1024 x 768), to give maximum clarity
A high-contrast theme was selected, to greatly improve display contrast
What’s next?
With the successful close of this proof-of-concept, [Justin] and [TJ] now have another clear option to make use of their vintage test equipment: a VGA Bare ready to mount inside their device, or a beautifully encased VGA Connect (à la Oscilloclock Connect).
But to make this truly production-worthy, a few improvements are needed:
Output voltage level adjustments, fully independent for X, Y, Z
A higher-voltage Z amplifier
Independently invertable X and Y signals
Reduction in the ‘ghosting’ or ‘ringing’ effects currently observed
Improved contrast and avoidance of ‘washout’ seen between pixels
Digital HDMI input !
… all added to Oscilloclock’s ever-growing backlog of things to do!
Do you want to play your favourite classic game on your old XY monitor? Do you want to stack 10 oscilloscopes on your shelf and have them all showing Matrix code? Or put your Grandpa’s old scope on your desk at work and have it display your Outlook calendar?
Our mantra makes it possible: Just. Because. We. Can.
A modern military-spec connector from France meets an ancient Bakelite connector from Japan. It’s love at first sight! The two are joined together in eternal conductivity. Not by a priest, but by eleven 3kV silicon wires surrounded in a lustrous braided sheath…
… Or so goes the story. There are other accounts, but we like this one best!
Diversity and distinction
Serious readers will have recognized the above harness, as it was used in Exo series Oscilloclocks such as the recently featured Exo 3KP1.
The Exo series. CRT and Control Unit must mate!… and this is how it’s done.
The Gold standard
We’ve crafted all kinds of harnesses for other Oscilloclock models. This one below takes the cake! Check out the chrome connectors, gold-plated pins, IP68 compliant clamps, and fray-resistant sheathing.
The ultimate in extravagant cabling! Why not?As used in the stunning Model 1-S
Simple and functional
Coming back down to earth, we have a less extravagant, highly functional connectivity solution for the Model 1 series:
No gold or chrome. But still military-spec and very solid. A joy to plug and unplug!… As used in this Model 1 130BXB31
Crazy cabling
NO single Oscilloclock used more cabling than the infamous AfterShock Clock! This consisted of two complete Oscilloclock Core sets integrated together to drive a dual-gun CRT.
The AfterShock Clock in its initial form. Have you ever seen so many cables?
The harnesses supplied in this first delivery were… raw, to say the least.
Later, as [Atif] worked on his AfterShock Clock’s case, he ordered a set of production quality cabling: two CRT harnesses, and one custom interconnect cable to join the two control units together. Beautiful!
Fixated on the affixed
At another point on the spectrum of craziness are harnesses that are not fully removable. Below we have the incredible OscilloBlock Summer Dusk Edition, where the cabling enters the Lego-built Control Unit via a grommet:
There are more designs to show. But let’s move on to an important topic!
A safety consideration
Some Oscilloclocks, especially those in the Exo series, are designed to physically expose the CRT as much as possible to the happy owner and his/her entourage of vintage electronic aficionados. They can touch. Feel. And even listen. (Yes! Some CRT electrodes can even emanate sound!)
An Exo 3KP1 needs 2.2kV to draw this!
But many readers may also know that cathode ray tubes operate at high voltages. In fact, in the baseline Exo 3KP1, some pins of the CRT are supplied with roughly 2,200 volts compared to other pins.
Now, clever readers may have noticed in photos of the assembled Exo 3KP1 that there is a slight gap between the socket and the base of the CRT. The metal pins are slightly exposed. If someone or something somehow bridged that gap – with prying fingers, paws, coffee, or dust – the results could be serious.
Never fear! There is an insulating o-ring (gasket) that was not installed at the time the Exo photos were taken. It’s a very basic but effective solution. See these instructions from the Operating Manual:
Installing the ubiquitous o-ring
We don’t have enough hours in the day to talk through all the safety considerations. But they include:
usage of high voltage tolerant silicon-sheathed wires
selection of military-spec connectors rated for high-voltage use\
a clever pin layout that minimizes the voltage difference between any given pin and its neighbors
We’re proud of our harnesses. And you can be too.
And that’s a wrap!
Are YOU haplessly hooked on harnesses? Does capably-crafted cabling captivate you? Stay tuned! Next time we craft up a CRT harness, we’ll snap a few photos along the way. It’s a surprisingly deep topic!
No! We’re not here to talk about a new Star Wars character! The 3KP1 is a type of cathode-ray tube that was used in many low-cost 1960s-1970s Japanese oscilloscopes.
And the Exo is a series in our Oscilloclock range that fully exposes the CRT both visually and physically, much to the delight of the owner and visitors – while of course protecting high voltage areas from dust and prying fingers.
The Exo 3KP1!
First crafted for [Jerry] back in 2019, the Oscilloclock Exo 3KP1 is the default character in the Exo series, alongside the arguably oddball Oscilloblock – Summer Dusk Edition and the slightly more exotic OscilloTerm Exo B7S4.
There’s nothing more soothing than the green glow of flourescent phosphor backed by the amber ambience of the CRT heater. Ahhh, that’s nice.
This Exo shipped with all the “standard” screens, like the analog clock face below. But why stop there? We’ve done custom logos, movie themed features, oddball time systems, and so much more!
From the top, [Jerry] and his dinner guests can readily inspect every square centimeter of the CRT and its exquisite innards. Cooool.
Inside the unit, neatly tied cabling lends an air of gentle sophistication, while the green of the circuit boards harmonizes well with the phosphor.
Even as a baseline model in the series, the Exo 3KP1 is distinctly attractive.
[Jerry] did make some choices along the way, including which CRT to use. Let’s explore his CRT options in more detail!
Round vs. flat
The flat-faced 3KP1(F) version
As shown in the photos, the CRT that [Jerry] selected has a slightly convex face. This was the standard shape of the original 3KP1 type CRT, and is a perfect choice for the Exo case style, as it visually softens the glass edge exposed in front of the acrylic ring supports.
The round-faced 3KP1 was superseded after some years on the market, by a flat-faced version: the 3KP1(F). This version is rather more commonly found and they are delightful to use. We used a 3KP1(F) in the Exo series Oscilloblock, as shown at right.
Which would YOU prefer – round or flat?
Phosphors and flavours
[Jerry] had another choice to make: the phosphor! While the standard phosphor of most CRTs of the day was green, other colours were available such as amber, blue, white, purple. Such CRTs are more rare, but we have some… and so could Jerry!
Phosphor diversity. What would [Jerry] go for?The “trailing effect” on a long-persistence CRT
There were also varieties of CRT with different persistences; i.e., how long the trace would continue to show on the screen! We love this shot of the moving second hand on a blue, long-persistence CRT:
And, we just happened to have a 3KP7 CRT in stock with exactly these characteristics.
But in the end, [Jerry] wanted the nostalgic look of an old green-screen computer monitor, and chose the stock-standard 3KP1.
Nice choice!!
The longevity question
[Jerry]’s clock shipped with a used 3KP1 CRT. Pre-owned, pre-loved, and pre-21st century.
But we don’t sell junk. [Jerry]’s CRT was selected for its unblemished phosphor, and for its still-bright and vibrant performance. And, of course, there is the standard warranty of 1 month for a used CRT:
But the question often comes: “How long will a CRT really last?”
Here at Oscilloclock we don’t mince words, and we don’t use euphemisms (much!). But the fact is this – after 15 years of crafting Oscilloclocks for customers around the globe, no-one has reported having to change their CRT. Maybe it’s happened and we are oblivious. Even better!
Our secrets to CRT longevity are:
We select only the highest quality CRTs, made by reputable manufacturers. [Jerry]’s CRT was manufactured by Toshiba, a key supplier of the day.
We check CRT specifications carefully, and avoid those with any hint of short lifetimes. (Some CRTs had very short expectancies, such as 1000 hours! Perhaps these were used for demanding applications where even a tiny degradation in performance could not be accepted.)
Oscilloclocks employ a soft-start mechanism to minimize stress on the CRT heater.
The Spare
Notwithstanding our facts around longevity, [Jerry] decided to plan ahead for an eventual CRT replacement. He purchased a stunning new-old-stock Hitachi 3KP1, with quality certificate and even in its original box.
They don’t get more original than this!
But is a Hitachi 3KP1 better than a Toshiba 3KP1?
We’ve compared them, and couldn’t tell any difference in performance or characteristics. We did notice one thing, though: the Hitachi is significantly heavier than the Toshiba. Hmmm….
One day, we’ll dissect some (defunct) units, and get to the bottom of that odd observation. Stay tuned for a post!
Like what you see? [Jerry] did. Check out our other creations!
