Toshiba Transformed

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!

Toshiba ST-1248D Oscilloclock

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

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.

Toshiba ST-1248D - Brass bezel

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!

260+ individual components. Lovingly hand-mounted by yours truly!

260+ individual components. Lovingly hand-mounted by yours truly!

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!

Toshiba ST-1248D Oscilloclock - Tubes

Toshiba ST-1248D Oscilloclock - Underneath

Under the Oscilloclock! Try to spot where the original HV supply has been disabled…

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:

Toshiba ST-1248D Oscilloclock - Adjustments

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

Toshiba ST-1248D Oscilloclock - Boards pulled out

12m of 3kV melt-proof silicone wire!

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…

Toshiba ST-1248D Oscilloclock - Control installation

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

Toshiba ST-1248D Oscilloclock - GPS connector

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!

Toshiba 3KP1(F) Original Inspection Certificate 1965

The spare CRT actually has a pedigree – an original inspection certificate from 20 January 1965!

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.