Old ephemeral tech that almost was | Poal: Say what you want.

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V‑FETs / SITs (Static Induction Transistors)

A rare class of solid‑state devices from the 1970s that behaved much like vacuum‑tube triodes, offering smooth transfer curves, soft clipping, and exceptionally low distortion without heavy feedback. Used mainly in high‑end Sony and Yamaha audio amplifiers.

What happened:

Extremely difficult and expensive to manufacture
Low production yields and tight tolerances
MOSFETs became cheaper, more rugged, and easier to scale
Market too small to justify continued fabrication

They’ve since become legendary among audiophiles

Unijunction Transistors (UJTs)

An interesting device used for timing, oscillators, and triggering circuits in the 1960s–70s.

What happened:

MOSFETs and programmable
ICs replaced their niche
Poor temperature stability Limited flexibility

You almost never see one in modern hardware.

Tunnel Diodes

These were wild: they use quantum tunneling to create negative resistance, allowing oscillators in the GHz range long before modern RF tech.

What happened:

Hard to manufacture consistently
GaAs and CMOS RF took over
Sensitive to heat and static

SCR-based Logic (Complementary SCR Logic)

Before CMOS, some engineers experimented with logic families built from silicon-controlled rectifiers.

What happened:

Slow
Latching behavior made them awkward
CMOS was cheaper, faster, and easier

It’s like an alternate universe where computers ran on tiny thyristors.

Magnetic Amplifiers (Mag-Amps)

Used in early computers and power supplies, these used saturable inductors to amplify signals without vacuum tubes.

What happened:

Transistors were smaller, faster, and cheaper
Mag-amps were bulky and heavy
Limited bandwidth

They were trendy in the 50s.

Nixie Tubes

Glowing neon numeric displays that look like retro sci‑fi props.

What happened:

LEDs and LCDs were cheaper and more efficient
High voltage required
Fragile glass construction

They’ve made a comeback, but only as art.

Thyratrons

Gas-filled tubes used as high-power switches and pulse generators.

What happened:

Solid-state devices replaced them
Bulky and required warm-up
Limited lifespan

They were the "IGBTs of the 40s."

Parametric Amplifiers

Used in early microwave and radio astronomy systems, these used variable reactance to amplify signals with extremely low noise.

What happened:

Semiconductor low-noise amplifiers became superior
Complex and finicky
Required exotic pump frequencies

They were cutting-edge for a moment.

Gas Discharge Logic (Dekatrons, Trochotrons)

Mechanical-looking counting tubes used in early calculators and counters.

What happened:

Transistors made them obsolete overnight
Slow
High voltage and fragile

They’re mesmerizing to watch, though.

Cryotron Logic

Superconducting switches used in the 1950s as a potential replacement for vacuum tubes.

What happened:

Required liquid helium
Transistors improved too quickly
Manufacturing was impractical

Arrived 60 years too early.

Nickel–Iron Transistors (NiFe Transistors)

A short-lived attempt to make transistors from unusual materials in the early solid-state era.

What happened:

Silicon and germanium dominated
Poor performance
Difficult to scale

They’re now mostly forgotten.

## V‑FETs / SITs (Static Induction Transistors) A rare class of solid‑state devices from the 1970s that behaved much like vacuum‑tube triodes, offering smooth transfer curves, soft clipping, and exceptionally low distortion without heavy feedback. Used mainly in high‑end Sony and Yamaha audio amplifiers. What happened: - Extremely difficult and expensive to manufacture - Low production yields and tight tolerances - MOSFETs became cheaper, more rugged, and easier to scale - Market too small to justify continued fabrication They’ve since become legendary among audiophiles ## Unijunction Transistors (UJTs) An interesting device used for timing, oscillators, and triggering circuits in the 1960s–70s. What happened: - MOSFETs and programmable - ICs replaced their niche - Poor temperature stability Limited flexibility You almost never see one in modern hardware. ## Tunnel Diodes These were wild: they use quantum tunneling to create negative resistance, allowing oscillators in the GHz range long before modern RF tech. What happened: - Hard to manufacture consistently - GaAs and CMOS RF took over - Sensitive to heat and static ## SCR-based Logic (Complementary SCR Logic) Before CMOS, some engineers experimented with logic families built from silicon-controlled rectifiers. What happened: - Slow - Latching behavior made them awkward - CMOS was cheaper, faster, and easier It’s like an alternate universe where computers ran on tiny thyristors. ## Magnetic Amplifiers (Mag-Amps) Used in early computers and power supplies, these used saturable inductors to amplify signals without vacuum tubes. What happened: - Transistors were smaller, faster, and cheaper - Mag-amps were bulky and heavy - Limited bandwidth They were trendy in the 50s. ## Nixie Tubes Glowing neon numeric displays that look like retro sci‑fi props. What happened: - LEDs and LCDs were cheaper and more efficient - High voltage required - Fragile glass construction They’ve made a comeback, but only as art. ## Thyratrons Gas-filled tubes used as high-power switches and pulse generators. What happened: - Solid-state devices replaced them - Bulky and required warm-up - Limited lifespan They were the "IGBTs of the 40s." ## Parametric Amplifiers Used in early microwave and radio astronomy systems, these used variable reactance to amplify signals with extremely low noise. What happened: - Semiconductor low-noise amplifiers became superior - Complex and finicky - Required exotic pump frequencies They were cutting-edge for a moment. ## Gas Discharge Logic (Dekatrons, Trochotrons) Mechanical-looking counting tubes used in early calculators and counters. What happened: - Transistors made them obsolete overnight - Slow - High voltage and fragile They’re mesmerizing to watch, though. ## Cryotron Logic Superconducting switches used in the 1950s as a potential replacement for vacuum tubes. What happened: - Required liquid helium - Transistors improved too quickly - Manufacturing was impractical Arrived 60 years too early. ## Nickel–Iron Transistors (NiFe Transistors) A short-lived attempt to make transistors from unusual materials in the early solid-state era. What happened: - Silicon and germanium dominated - Poor performance - Difficult to scale They’re now mostly forgotten.

[–] • 1 pt

(edited )

Mostly forgotten?

UJTs are the base building blocks of inexpensive oscillators. Relaxation oscillators are for UJTs.

Thyratrons were obsoleted by triacs and SCRs. There were in no means "almost was" technology - they were for their time. An 885 is still a useful tube even though it hasn't been made for the better part of a century.

Tunnel diodes are still used for particular applications in microwave and FM devices.

Magnetic and parametric amplifiers with variable reactors are still used, just not in stuff you need to know about.

NIXIEs were wildly successful. They were, not almost was. There were even ICs to drive them.

Pretty much nothing on here almost was - it was for it's time with exceptions for some of the more experimental technology. Just because newer technology came along doesn't mean anything. By that reckoning, a carburetor almost was, even though it was used for a century before injection became cheaply feasible.