Turning Grandpa’s o-scope into a clock


Around 1960, [Aaron]’s grandfather decided to try his hand at a new career in electronics repair. It didn’t pan out, but before he gave up he built a beautiful Heathkit oscilloscope, a model OR-1. Grandpa’s electronics career never took off, but years later it would serve as the impetus for [Aaron]’s own career in electronics. Now [Aaron] has too many oscilloscopes, but still wanted a way to preserve his grandfather’s legacy. An oscilloclock was just the project to do that.

Of course to turn an oscilloscope into a clock requires some interesting control circuitry, and [Aaron] didn’t skimp on his build. He created a custom control board that is able to draw any shape on the CRT screen using just circles; squashing circles to draw a line, and cutting the beam entirely to slice a circle in half.

This isn’t [Aaron]’s first oscilloclock by a long shot. He previously created this amazing clock completely from scratch. Still, using Grandpa’s old tools is a great way to make this oscilloscope useful again, even if [Aaron] is already up to his gills in test equipment.

27 thoughts on “Turning Grandpa’s o-scope into a clock

  1. How about an interface to use it as a vector scan arcade monitor to play Asteroids, Space War, Armor Attack and other old games on? A round screen would be just the thing for Star Castle.

  2. That’s a gorgeous display, and a truly great use for a classic Heathkit oscilloscope. I congratulate you on an excellent project!

    Addressing comments from your other o’scope clock: Phosphor burn shouldn’t be a problem because the Heath power supply isn’t regulated; the beam will drift around on its own. That, and not running at high brightness all the time should be enough.

    Vector displays are much older than you’d think. They existed before ICs, and even before transistors, in the vacuum tube days. I remember a WW2 vintage digital clock project that used a CRT and stepping relays! The characters were formed by Lissajou figures with only passive waveform shaping components (resistors, capacitors, diodes, and 60 Hz AC.

    “Sourcebook of Electronic Circuits” by John Markus has a whole chapter with dozens of circuits for doing this sort of thing if you’d like to see how Grandpa would have done it. :-)

    1. Lee, thanks and glad you liked it! Phosphor burn isn’t a problem, but not because of the Heathkit’s circuitry. I’ve left the circuit completely intact (and you can turn it on to see the tubes light up, but the CRT is powered directly from a set of Oscilloclock boards. These are extremely well regulated and use very tight tolerance components throughout. Burn-in is instead reduced by applying a (different) small position offset to the image every hour.

      I love the idea of using passive components for lissajous character generation.. I have seen some examples, but never involving stepping relays! One day I will try it!

    1. Ya shouldn’t need more than 2 of anything. I find that I end up diagnosing the problem with a multimeter long before I haul it over to a friend’s o-scope to confirm my findings. To each their own, though.

      1. Not with a scope. I have a two portable units, both battery powered, one analog, one digital. I also have two other scopes, a TDS340A and a really nice TDS754C. The is nice and light an can be easily moved but the 754 is really heavy. They all have their uses.

    1. Hi Drone, see my response to an earlier comment, but indeed the image is moved around every hour. The CRT heater is likely to go before the phosphor, although even at 24 hours per day I anticipate at least a couple years of use with a quality CRT. The clock has configurable auto power off, to save the tube and also some energy (approximately 12-15W for this large size).

      But good idea, I’ll get it to bounce around the edges for the effect!

      1. It might be a little kinder on tube life if you had a timer that dimmed/killed the tube during night hours (i.e. when you’re asleep), or a motion sensor that only fired up the screen for x time, when someone walks into the room perhaps.

        Seriously mouth watering blend of tech though dude, well played!

        1. Okay, the motion sensor idea is now definitely on my list of cool things to do!! (Timer on-off operation to come first…) I really must work on an improved design with more I/O available for sensors and other communications. Thanks for the nice comments!

          1. Tubes (like light bulbs) last a lot longer if you don’t keep turning them on/off. The filament draws a huge inrush current at turn-on that stresses it and shortens life. If you feel you must cycle it on/off several times a day, add a soft-start circuit. This can be as simple as a series resistor on turn-on that gets shorted by a relay contact once the filament has warmed up.

          2. Lee, that’s an important point about inrush current. In this clock I’ve incorporated a crude inrush current limiter, in the form of a few 6.3V pilot lamps (paralleled) in series with the heater. The Oscilloclock Power Board provides around 6.6V RMS and after warmup there is a decent 6.1V rms getting to the CRT, which is just right!

            My next post will have more details including a video of the limiter lighting up and a pic of the voltage trend over 10 seconds. Stay tuned!

          3. Great to hear that you have a filament soft-start circuit. That goes a long way toward longer life if you must switch it on/off several times a day.

            Everything in the design of a tube is a balancing act. The designers had decades to learn, and tweak them for the best tradeoffs between performance, life, and cost. If you use a tube outside of its intended specs (different voltages, currents, etc.) unexpected things can happen that shorten its life.

            Too low a filament voltage, or too low a cathode current for extended periods will shorten life. The electrons boiled off the cathode need to go somewhere; otherwise they will bombard the heater, and damage its emissive coating. So these are not good ways to dim your CRT. You can reduce the beam current; but don’t reduce it to zero — just to a point of low brightness.

            After all, saving the phosphor but poisoning the cathode in the process just changes the end-of-life to a different failure mode.

  3. Very nice design and execution! The scope appears to be in excellent cosmetic condition, too. Well, done, and I echo the sentiment of the other poster: your grandfather is very proud of you right now!

  4. I’d bet some money that that scope design started with Tektronix- the knobs, panel layout and general look of the thing just screams early 60’s Tek. And their designs back then were highly amenable to kitting . . .

    1. There is no way the owner would have anything to do with a kit machine. Closer to Bell & Howell than Tek. Tek made almost everything in house, knobs, screws, crts, etc. Pretty much everything that wasnt a generic discrete component. They outsourced the knobs once and they were terrible and they got CRTs from another manufacturer and they were terrible, so they tried to keep everything in house.

      I see tons of Tek stuff around where I live – Tek is within walking distance of my house. My cnc mill came out of their model shop and I just got a laser welder that was originally bought in 85 to put together the MCP CRTs for the 2467.

      1. Heath Company was very well connected to the big electronics manufacturers. Many of their customers were engineers at these firms! So Heath often got permission to build legal “clones” of top quality products like Tektronix ‘scopes, Fluke multimeters, Hammond organs, Collins ham gear, etc.

        Heath’s ‘scopes were functional copies; not exact copies. They had to re-engineer them to use readily available parts and for hand assembly. They often sold for almost as much as the “real thing”, so they were no threat. The appeal was that you could build and fix and modify it yourself. Heath’s kits were *intended* for hacking! :-)

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