It is July 16. The sun is a diesel-powered furnace welded directly above your skull by a malevolent engineer who clearly never had to work outdoors. Heat indexes are lying to you in real-time. Somewhere, a politician is promising relief that will never come. The ice in your drink surrendered eleven seconds ago. This is Summer, raw and unprocessed.

Now watch what happens when I apply the Formulae.

Apply the Omega7Red Formulae and Summer becomes: brass valves bleeding off overpressure steam on a copper boiler the size of a cathedral, zeppelins trailing condensation over a crowd in full kit (goggles down, corsets tight, nobody sweating because the aesthetic demands it), the smell of machine oil and gunpowder and something that is definitely not legal at a county fair. It is SteamPunk Summer: oppressive, gorgeous, completely worth it. Whitby XX just wrapped. Papplewick Pumping Station turned ten. The Brass Screw Consortium has already convened and dispersed. TeslaCon is heading to Oz. The Formula is running hot this year, and for once, that is not a complaint. High-5. Stay hydrated. Nothing can beat old age and betrayal.

Glowbug is the term given to describe Amateur Radio operators (HAM) and sometimes their equipment because of their fondness for vacuum tube electronics.  This cute little toy oscilloscope is completely operational and uses vacuum tubes to drive its 7cm CRT. The casing is wood, and the brass fittings add a nice touch. This is actually a Mark II variant of an earlier design.

The schematic shows a pretty simple, yet brilliant pentode-based circuit, and the engineer is happy to explain the circuit in stunning detail.  I could build one in my sleep after many hours of lost sleep:

It uses three different small-signal rf pentodes – an EF91 in the timebase circuit, an EF184 in the Y amplifier, and an EF80 in the X amplifier.  The choice of tubes is somewhat arbitrary. The EF91 would be very suitable in all three functions since, among small-signal pentodes, it is unusual in having suitable characteristics for providing a relatively large anode voltage swing with little distortion.  But I do not find the EF91 visually attractive, so I opted for the other tubes in the main functions, relegating the ’91 to the back of the chassis, where its smaller size fits in nicely.  The EF184 has high transconductance, so is used in the Y amplifier where large voltage gain is required, while the EF80 is used with cathode-degeneration feedback in the X amplifier which requires much less gain, but a larger voltage output with good linearity.

Details: http://g4oep.atspace.com/toycro/toycro.htm#Mark II version with Added Brass [broken link]