Burn-in? Nope!

Many folks have asked whether screen burn-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.

  1. 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.

  2. 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!

  3. 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!

X-Y-Z Core – Revamped

Avid followers may have noticed an absence of fresh posts recently… What gives?

I’m happy to report that it’s only because Oscilloclock has been absolutely run off its feet in 2016, producing more crazy CRT based devices than ever before. There just hasn’t been time to do justice to the blog!

The good news here is there are lots of posts in the backlog. Let’s start out with this one:

Yet Another CRT clock fanatic?

I was approached by [Mike], who wanted to design his own CRT clock from scratch, but didn’t want to mess with the high voltage circuitry involved. Could I help out with an X-Y-Z display assembly, and he would do the rest? You bet!

Here is the newly revamped Oscilloclock X-Y-Z Core, shipped out in Q2 2016:

Oscilloclock XYZ Core

And here is what [Mike] was able to with it, after implementing a totally fresh controller design incorporating Circle Graphics:

oscilloclock-xyz-core-customer-clock-implementation-01

[Mike]’s setup – A home-grown controller board, the X-Y-Z Core, and a 3KP1(F) CRT

Here is [Mike’s] story in his own words:

I was thinking of building a Nixie clock, but when I discovered the vector graphic clocks that Aaron and others had built, I knew I needed to build one. I felt comfortable that I could recreate my own version of the digital logic and the low-voltage analog signals, but didn’t really want to tackle the deflection amp or the high voltage circuitry. Buying the Oscilloclock XYZ display solved that problem. Everything arrived as and when promised, and I was beyond impressed by the care and workmanship that’s evident in everything from the boards to the harnesses to the documentation!

I based my controller board on a Cypress PSOC 5LP chip, which allows me to implement all of the digital logic in its on-board programmable logic fabric. The 80MHz 32 bit ARM processor allows me to program 100% in C, which enabled me to create my own version of the software fairly easily. (I tip my hat to those who have done it all in 8-bit assembly!)

Remaining work includes improving my signal quality, which doesn’t yet fully exploit the bandwidth and linearity of the Oscilloclock boards, designing an interesting enclosure, and adding a few software features.

Good luck [Mike] with the rest of your implementation!!!

Key features

This unit is the latest incarnation in a series started in 2015, for a client who needed a custom Head Up Display solution. The boards have undergone through several revisions since then to optimize performance. This particular kit was pre-configured and fully tested to support 3RPx, 3KPx and 3WPx CRT types, and features:

  • Cathode to deflection voltage of 1875V
  • Digital blanking (grid modulation), safely isolated at 2.2kV continuous working voltage
  • Precision deflection amplifier capable of driving +/- 275V with 0.1% linearity
  • 0-5V analog X and Y inputs with 2.5V reference output [Option RS]
  • TTL/CMOS compatible high-frequency blanking input
  • Dim/Bright digital input with PWM support
  • Power Off digital input
  • Temperature-controlled fan with Failure and Overtemp safety features
  • CRT rotation coil supply (+/-5V)
  • CRT heater soft start / inrush current limiting
oscilloclock-xyz-set-16001-01-01

Oscilloclock X-Y-Z Core set – as shipped


Like what you see?

X-Y-Z displays are cool. But so are my other unique creations! See the Gallery, and stay tuned!

Kikusui Time

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!

Kikusui 537 Oscilloclock

See this in HD, and find more exciting videos on my YouTube channel

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.

Kikusui 537 Oscilloclock

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!

History

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).

Kikusui Logo

The Kikusui Electronics Corp. logo

Construction highlights

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!

Kikusui 537 Oscilloclock - inside top

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

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!

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:

Kikusui 537 Oscilloclock - control (original)

Sweep adjust control in its original state

After removing the potentiometer

After removing the potentiometer

The encoder, after hacking with a hacksaw!

The encoder, after hacking with a hacksaw!

Kikusui 537 Oscilloclock - control mounted

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!

More 2015 craziness – the CopperClock!

Happy New Year! Looking back, 2015 was a superb year, full of fun and fancy. And just in case you thought last year’s creative juices were exhausted by the fabulous Oscilloblock, rest assured that there was an even crazier creation – the 2015 luxury edition CopperClock!

CopperClock on shelf 01

The unusual facade for this unit was built to order by a Canadian craftsman specializing in hand-hammered and silver-soldered copper weather vanes. If you enjoy metal art, you will certainly approve of this!

Oscilloclock CopperClock 01

But… you may have read my previous articles and know that three-inch Oscilloclock models are typically powered by 2.1kV high voltage power supplies. Isn’t there any danger in using a metal case?

Never fear! The internals are fully encapsulated in a beautiful cast acrylic case, providing full insulation and utmost safety.

Oscilloclock CopperClock - internals 01

Breaking from tradition, I’ll refrain from describing other features of this unit (such as the selection of a round-faced CRT to give it character), and instead just post a few more photos of the clock ‘in situ’. Enjoy!


The 2015 CopperClock atop a beautiful Philips Radioplayer. What a match!

... or perhaps atop a vintage Estey pump organ?

… or perhaps atop a vintage Estey pump organ?

... perhaps it looks best on a 1920's Edison Diamond Disc Phonograph!

… perhaps it looks best on a 1920’s Edison Diamond Disc Phonograph!


Like what you see?

This exquisite specimen is currently available to someone with a metallurgical and chronometric disadvantage. Visit the Availability page for more information, and of course see the Gallery for other unique creations!

Heads Up!!

Recently I received a most intriguing request: I was asked to build a self-contained, super-bright X-Y display unit with 3-inch CRT, for use in an “HUD“. Hmm…

Holographic Utterance Device?
Horizontally Unstable Doohickie?

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.

HUD in an F-18 aircraft. Source: AC Aviation Life

HUD in an F-18 aircraft. Source: AC Aviation Life

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!

Oscilloclock 3-inch X-Y-Z display, custom-built for an HUD

An Oscilloclock 3-inch X-Y-Z display unit, optimized for use in an HUD

Continue reading

A Humpty Dumpty CRT

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

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!

Looking down the barrel. Imagine you are a phosphor molecule, with projectiles from this gun hitting you at the speed of light!

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VectorClock Reloaded!

Aside

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)

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!

Be sure to check out videos on my YouTube channel.

Robbie’s Place

What do you do on a mundane business trip to London?

Why, shopping, of course! But if you were the humble proprietor of Oscilloclock.com, you would do much more than that… You would seek to expand your vintage electronic empire!

And so it was that I found myself hunting old electronic devices on Portobello Road one fine Saturday morning. Unfortunately, the game there was far and few between; only two relatively mediocre valve radios, in even more mediocre shape, at far more than mediocre prices…

Fortunately, my colleague was going to save the day. “Pop out to Cambridge for a visit – I’ve seen a few antique shops here,” said he. And after the hour train journey and a wee but of walking, we stumbled onto a veritable gold mine – Robbie’s.

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VGA display… On a 3″ scope tube!

Yes, you’ve all thrown away your lunky old CRT monitors, in favour of sleek ultra-thin LCD displays. And, you thought you’d never see another one again…

But this CRT display has a twist! It’s round. It’s small at just 3 inches diameter. And it’s awfully cute.

Oscilloclock 3-inch CRT VGA Display Assembly - overview

Last year, I was approached by a dedicated flight simulation enthusiast, who needed a radar indicator to use in a fighter cockpit replica. The indicator should employ a CRT, for the most realistic look. Could Oscilloclock design and construct such a display?

It didn’t take much convincing! Diverging only temporarily from building clocks, I took up the challenge to create my first raster-scan CRT display unit. In the ensuing months, difficulties sprang forth from every direction in the project, but ultimately I was able to avoid a diraster (sic) and deliver a functional assembly:

See more related videos on my YouTube channel

The Setup

The key component of this setup is a new prototype VGA Board that converts a VGA signal into analogue X and Y outputs. Both analogue intensity and binary blanking outputs are provided.

Oscilloclock VGA Board prototype

Oscilloclock VGA Board prototype

The X and Y outputs drive an Oscilloclock Deflection Board, while the binary blanking output drives the blanking amplifier in a CRT Board.

Oscilloclock Deflection Board - modified for ultra-linear HV output

Deflection Board – modified for ultra-linear HV output

CRT Board - heavily modified for improved frequency response

CRT Board – modified for improved frequency response

Blanking isolation, heater, and HV supplies are provided by a Power Board.

Power Board - with improved optocoupler

Power Board – with improved optocoupler

It all looks so easy! But noooo. Astute readers will recall from other posts that every Oscilloclock project involves sleepless slumbers, horrific hair-pulling, and forgotten family members. Let’s see what caused me grief this time…

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