Beyond the power variant, it sometimes seems as though we rarely encounter a discrete transistor these days, such has been the advance of integrated electronics. But they have a rich history, going back through the silicon era to germanium junction transistors, and thence to the original devices. if you’ve ever looked at the symbol for a transistor and wondered what it represents, it’s a picture of those earliest transistors, which were point contact devices. A piece of germanium as the base had two metal electrodes touching it as the emitter or collector, and as [Marcin Marciniak] shows us, you can make one yourself (Polish language, Google Translate link).

These home made transistors sacrifice a point contact diode to get the small chip of germanium, and form the other two electrodes with metal foil glued to paper. Given that germanium point contact diodes are themselves a rarity these days we’re guessing that some of you will be wincing at that. The video below is in Polish so you’ll have to enable YouTube’s translation if you’re an Anglophone — but we understand that the contact has to be made by passing a current through it, and is then secured with a drop of beeswax.

A slight surprise comes in how point contact transistors are used, unlike today’s devices their gain in common emitter mode was so poor that they took instead a common base configuration. There’s a picture of a project using three of them, a very period radio receiver with bulky transformers between all stages.

If you’re interested in more tales of home made early transistors, read our feature on Rufus Turner.

Thanks [Dr.Q.] for the tip.

When thinking of the first PCs, most of us might imagine something like the Apple I or the TRS-80. But even before that, there were a set of computers that often had no keyboard, or recognizable display beyond a few blinking lights. [Artem Kalinchuk] is attempting to recreate one of these very early digital computers, the Kenbak-1, using as many period-correct parts as possible.

Considered by many to be the world’s first personal computer, the Kenbak-1 was an 8-bit machine with 256 bytes of memory, using TTL integrated circuits for the logic as there was no commercially available microprocessor available at the time it was designed. For [Artem]’s build, most of these parts can still be sourced including the 7400-series chips and carbon resistors although the shift registers were a bit of a challenge to find. A custom PCB was built to replicate the original, and with all the parts in order it’s ready to be assembled and put into a case which was built using the drawings for the original unit.

Although [Artem] plans to build a period-correct linear power supply for this computer, right now he’s using a modern switching power supply for testing. The only other major components that are different are the status lamps, in this case switched to LEDs because he wasn’t able to source incandescent bulbs that drew low enough current, and the switches which he’s replaced with MX-style keys. We’ll stay tuned as he builds and tests this over the course of several videos, but in the meantime if you’re curious how this early computer actually worked we featured an emulator for it a while back.