The Warm Glow of Hollow State Electronics!

Yeah, you read that right! If the early transistor slingers where all hoopla about their new fangled germanium switches which they called "Solid State" we must conclude that the grand old dame, miss thermionic tube, must be "Hollow state". The story of this little project started long before either of us was born. In a country school science lab sometime during the fifties students where building shortwave radios from little kits their teacher had ordered from a company called Graymark. One of those kits survived, unassembled and untouched until young Patrick found it in the cupboards of said science lab and asked the teacher if he could have it. Tubes having already passed into legend by the 90's the teacher accepted and Pat went home to build his very own shortwave radio. Unfortunately, the radio did not work, though from what I hear it could give nasty shocks when touched!!!

Three or four years ago Pat asked me if I could have a look at it maybe get it working or at least get it to do some kind of noise. It was a rather nifty circuit. A regenerative receiver for those who speak the language built around a 12AT7. Also included where a 35W5 as rectifier and a 50C5 as audio power amplifier. If you heard about the all american five radios then you know the first problem with this one. Yep, that's right no transformer to isolate the incoming AC therefore the chassi was live!!!! No wonder one could contract a nasty shock! The second problem was a burnt out component, unfortunately one of those tube era components that now cost a small fortune, the rest of the world having moved on to transistor technology in their quest for massed produced, disposable electronic devices. Conclusion: radio cannot be fixed unless we throw money at it.

A few weeks back Pat and I where discussing bass guitars and amplifiers and how it would be nice to have a small tube amp to practice with at home. I mentioned that we could probably build a small amp out of his little radio that had been gathering dust on the top shelf of one of my bookcases for a couple of years. Eureka! Let's make a 1.5Watt tube monster (hahaha!) as a practice amp. So we gutted the small radio keeping all the good bits out of it. Elaborated a schematic out of ideas found on the net and spent a nice sunday afternoon breathing rosin flux fumes while soldering parts.

It's not quite done yet and I'll show you pictures of the finished "thing" once we get it going.