Connect !!

These days, just about everyone has an old oscilloscope lying around. You know, an old, dusty, derelict scope handed down from Grandpa (or Grandma). Well, [Paul] had something even better – an old Tektronix 602 X-Y Monitor! Could an Oscilloclock Control Board drive this vintage beauty? Absolutely. Could I make an aesthetically pleasing case? Definitely. How about time sync via WiFi? Stock standard!

Presenting the Oscilloclock Connect:

Here’s what it looks like plugged in to my fabulous old Tektronix 620 monitor:

And why not have a pair of Connects drive a Tek 601 and 602?

The Build

The main component of the Connect is, of course, a standard Oscilloclock Control Board. As usual, all 121 parts on Paul’s board were individually mounted and soldered by hand. The board then was programmed and underwent rigorous inspection and testing. Finally, the board was cleaned to remove flux and renegade flecks of solder, and sprayed with HV coating for humidity protection and – arguably more importantly – to give it its glorious sheen.

The case was custom-made and professionally machined right here in Japan from 6mm-thick sheets of pure cast acrylic (not extruded). This is an extremely transparent, hard, high grade acrylic – and Oscilloclocks deserve nothing less!

The case was sprayed with a special acrylic cleaner and static protection solution, before fitting the various components. Naturally, every part was cherry-picked, right down to the three BNC connectors – they needed an aesthetically pleasing colour, but they also had to have a shaft long enough to mount through 6mm-thick acrylic!

Finally, the physical interface! The knob was chosen for its perfect finger-fit and delicate aluminium/black tones, which gently contrast with the rest of the unit.

The Compatibility Crisis

Over the years, many folks have observed that the scope at hand has an “X-Y mode”, and asked if they could just ‘plug in’ an Oscilloclock Control Board. “Is it compatible?” Unfortunately, the response has usually been disappointing.

You see, creating figures and characters with Circle Graphics relies on the scope’s ability to turn the beam on and off at split-second intervals. This feature is called a “Z-axis input”. While many scopes from the 80’s and beyond do sport such an input, there are two common limitations:

Limitation 1: AC-coupled Z-axis inputs

Capacitive coupling – effective at isolating the input from cathode potential (-1260V !)

The input is connected to the CRT’s grid or cathode circuit via a capacitor. This is a low-cost, effective way to isolate the (usually) very high negative voltage of the grid circuit from the input.

The problem here is that the capacitor, by its very nature, removes the edges from the pulse. The controller is no longer able to control the beam on/off timing, and you end up with uneven blanking across the segments, as shown in the screenshot at right.

Depending on the values of the capacitor and the surrounding resistors, the symptoms may not be severe. However, the best way to resolve this problem (while still keeping the oscilloscope’s original circuit intact) is to insert an isolated DC blanking amplifier directly in series with the grid (or cathode). See the Kikusui 537 Oscilloclock for an example of this.


Most oscilloscopes tend to require at least +5V on the Z-axis input to noticeably blank the beam. The Connect, however, is only capable of delivering +2.5V. It works just fine if you set the scope’s Intensity control very low, but as you increase intensity, the blanking quickly becomes ineffective.

Below we have a beautiful Japanese YEW (Yokogawa Electric Works) 3667 storage scope. The left shot is misleading due to the camera exposure; the displayed image is actually extremely dim. The right shot shows the same* image with the intensity control increased – the image is bright, but there is no blanking!

* Astute readers will observe that the time is significantly different between the two shots. This is a result of the WiFi NTP sync kicking in right in the middle! More (or less) astute readers may also notice that the scope’s trace rotation is not adjusted very well…

Of course, it would be a simple matter to incorporate a pre-amplifier for the Z-axis, which would solve this problem. This will be introduced with the next Control Board revision!

Like what you see?

Nothing brings more joy than connecting this bundle of usefulness into a woefully unused old oscilloscope or X-Y monitor. If this is of interest to you, visit the Availability page for more information, and of course see the Gallery for other unique creations!

Tek 520A VectorClock!

Television broadcasting has switched from analog to digital – and if you’ve got a nice HD TV, you’ll be loving it!

But with that transition came the death of an entire breed of equipment – the Vectorscope.

Tektronix 1420 Vectorscope

Just to be clear, these are not monitors for playing ancient video games using vector graphics!!  No, the Vectorscope is (was) used to give a delightful view of the ‘vectors’ inside an NTSC or PAL video signal, describing the color components of the signal.

If you were lucky enough to be a TV broadcast technician, you’d use your Vectorscope all the time to check your vectors’ amplitudes and phase. You would even give your vectors names like ‘Jack’ and ‘Jill’, and check up on their relationships daily, just as any responsible guardian would!

But above all, you would marvel every single day at the beautiful hardware you were using, and the complex circuitry involved. Take a look at my Tektronix 526 Vectorscope, which has oodles of delicious tubes to heat my shop on a nice winter’s day:

Tektronix 526 Vectorscope

Well, it all went digital and there is no longer any need for analog color signal analysis. But dry your tears… There is something even better:

Announcing the Tek 520A VectorClock

This lovely Oscilloclock reincarnation of a Tektronix 520A, sold at Maker Faire Tokyo 2013, allows its new owner to forever relive the magic of NTSC, PAL and SECAM analog color.

Tektronix 520A VectorClock - brilliant blend of the old and new!

Tektronix 520A VectorClock – brilliant blend of the old and new!

See more related videos on my YouTube channel

The Tektronix 520A has a stunning built-in array of lights for illuminating the CRT graticules. By simply removing the bezel and external graticule, the Tek 520A morphs into a deliciously moody timepiece!

Tek 520A VectorClock - Glorious Glow

Normally, I shun CRTs with built-in graticules. Their lines detract dreadfully from an Oscilloclock image. But here! The Tek 520A’s internal vectorscope graticule is round! What better way to accentuate a Circle Graphics driven display?

Silky smooth Circle Graphics on steroids!

Silky smooth Circle Graphics on steroids!

Under the Cover…

The Tek 520A is solid-state. It can be left on 24 hours a day and not fail for many years. This makes it a perfect match for my Maximum Re-use + Minimum Invasion policy: nearly all existing circuits – HV power supply, deflection amplifiers, blanking – are put to use, with just a few (reversible) tweaks.

Tek 520A VectorClock - Maximum re-use, Minimum invasion

The Oscilloclock Power Board is mounted neatly next to its own dedicated low voltage supply. A small relay board can be seen below, for controlling the Tek’s main power unit. All cabling is HV-tolerant and neatly fastened with high-temperature cable ties.

Tek 520A VectorClock - Control Board mount and cabling

Of the more interesting reversible ‘tweaks’ needed for this retrofit, here we see a delightful little trimpot pretending to be a transistor. Quite an act, I would say!

Tek 520A VectorClock - an unorthodox transistor replacement

Like what you see?

If you love big, looming Vectorscopes and need to have one put to good use in your living room, Contact me. And be sure to subscribe from the front page, to track all the other exotic experiments and unique timepieces targeted for 2014!

Credits to [Quinn] in Canada, for providing the initial inspiration for the Tek 520A VectorClock project! site is open!

This site is dedicated to showcasing my Scope Clock designs, and to sharing technical information openly to anyone interested in these vintage electronic timepieces.

What is an “(Oscillo)scope Clock”?

A unique style of clock that displays the time (and other fun things) on a CRT taken from an old oscilloscope. These clocks operate on a fusion of old and new electronics, and are often housed in beautifully crafted cases of wood, metal, or acrylic.

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