› #13 of 30 · Foundations
Vacuum tube
The switch before the transistor
Comes after #12 Turing machine
Build the real thing
Real tubes from surplus sellers
Buy a few old vacuum tubes from a surplus or radio-parts seller and look inside: the heater, the cathode, the grid and the plate. The grid lets current through or holds it back, the job a transistor does today.
- Cost
- $ · Under $25
- Time
- One session
- Screens
- No screen needed
For the grown-up
Display the tubes unpowered: tube circuits run at voltages that can kill. Stick to common small radio tubes, never break one open (a few special tubes hold toxic or radioactive material), and a grown-up cleans up if one breaks.
Build it in bricks
Step-by-step brick booklets land one model at a time, starting with the Starter Five.
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