I believe in reincarnation. Every vintage device sporting a CRT deserves to live again, to be loved again, to lift someone’s spirits again. And in 2014, this beautiful Toshiba ST-1248D received its chance, born again as a suave Oscilloclock!

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Manufactured sometime in the mid to late 1950’s, the ST-1248D was extremely well-designed and assembled, compared to other compact models available on the domestic Japanese market at that time. The engineers considered both function and form – latched panels on the side and back, delicately laced wiring, and a relatively spacious interior conducive to heat removal and circuit reliability. But the delightful brass bezel is what really makes this one of the most beautiful Oscilloclock conversions ever.

The new owner’s corporate logo, being quite curvaceous, was terrifically appropriate for rendering in Circle Graphics! Even using the Oscilloclock Figure Creator, it took a good deal of trial-and-error to accurately portray the different line widths and shades of ‘grey’ required. But not a bad result!

Conversion highlights

In a previous post, I mentioned there are several general approaches to converting an oscilloscope. For a unit as venerable as this Toshiba, though, the only choice was to bypass all existing circuitry with a full set of latest-revision Oscilloclock boards. This allows for:

• Super-bright, sizzingly clear trace
• Ultra-linear deflection, rock-solid stability
• 10W nominal power consumption!

Naturally, the original circuitry is left almost entirely intact, with only the HV supply deliberately disabled. This allows the owner to turn on the original power switch and enjoy the delicious warm glow of lit valves!

At this point you must agree that the ST-1248D is a cute, compact little unit. But due to the size, it wasn’t possible to mount all five Oscilloclock boards facing outwards for easy access. So, three boards got the short stick, and had to be tucked neatly inside. Intensity, Focus and Astigmatism trimpots are therefore mounted vertically to allow in-situ adjustment:

Cables are also sufficiently long to allow the boards to be pulled out for maintenance and servicing.

Oscilloclocks need just one control. Where to install it? The Toshiba’s Sync switch was in just the right spot. But because this was a stacked switch + potentiometer control, with two concentric knobs, it was quite a challenge. To keep the external appearance unchanged, I removed the front wafer section and rear potentiometer, and installed the rotary encoder – allowing full re-use of the original shaft and mounting assembly. Invasive? Yes, but also fully reversible…

The only irreversible change in this conversion is the attachment of the GPS socket to the rear access panel. Hopefully a forgivable sin!

Spare CRT

The original CRT in this Toshiba was defunct, so I replaced it with an unused, new-old-stock CRT from the lab, and provided a nice 3-month guarantee. But beyond that, how long might a tube dragged from 40-year hibernation survive the torture of modern-day life?

Well, Oscilloclocks have several software and hardware features to avoid CRT burn-in and generally extend the life of the unit:

• Hourly XY shift setting
• Auto clock face change setting
• Auto power-off setting
• Soft-start power supply
• Series-lamp inrush current limiter

But even with these life-saving features, there’s really no telling. So I supplied a second CRT as a spare. And this tube even has a pedigree!

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Like what you see?

Oscilloscopes and other vintage CRT equipment are remarkably varied in size, shape, and ambience. There’s one out there that’s just right for your office, bedroom, restaurant or shack! Contact me if you’re interested in a custom reincarnation.