The Eyes Have It with This Solid State Magic Eye

The classic “Magic Eye” tuning indicator was a fantastic piece of vacuum tube technology that graced all kinds of electronic gear for a fair fraction of the 20th century. But despite its prevalence, finding a new-old-stock Magic Eye tube is a tall order these days, especially for the rare versions like the 6T5. No worries, though, since direct plug-in solid-state replacements for the 6T5 are now a thing, thanks to [Gord Rabjohn].

Readers will be forgiven if this seems a tad familiar, since the current work is based strongly on [Gord]’s previous Magic Eye work. But the 6T5 was a unique tube, with a display that looked more like a dilating pupil than the sweeping circle of the more common 6E5 and 6U5 tubes. Luckily, most of the basic circuitry of the previous tubes, which was based on the classic LM391x LED bar graph display chips, could be leveraged for the 6T5 substitute. [Gord] did need to come up with a new display board, which holds 160 green surface-mount LEDs in six concentric rings. He also added a single orange LED to the very center of the display board, to simulate the cheery glow of the original tube’s heater filament.

As seen in the video below, the solid-state circuit lives in the exact same base and glass envelope that the original tube used. The animation is pretty smooth, and the look is quite convincing. The color isn’t quite right, though, but that’s limited by the color of the LEDs. We wonder if a similar circuit using addressable RGB LEDs could get a closer match to the original 6T5 phosphor. Or perhaps just replacing the green LEDs with white ones and tweaking the tint of the diffuser would be an easier approach.

Not that we’re complaining, mind you; the solid-state substitutes came out great!

Thanks to [hackbyte] for the tip.