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
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.
LIMITATION 2: INSUFFICIENT BLANKING AMPLIFICATION
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!
