Every year at NAMM some new schlock is reintroducing a line of solid state devices just like the FETRON that plug into a 12AX7 or sometimes other tube sockets (usually the same pinout as a 12AX7) but they never ever stay around for long. Put an 18-0-18 or a 12-0-12 supply in a tube amp and run some JFET & MOSFET gain stages in it or use op amps or use any combination. The Dumble amps with the FET inputs used a quasi-universal TV repair JFET transistor from NTE. There are probably 30 to 100 transistors in the NTE book alone that that NTE transistor can adequately replace in a vintage TV set. Those might run at 30 or 40 volts or so. The FETRON is (A) not a vacuum tube, and (B) it's a pair of cascode transistors, with a buffer. That makes it very similar to a pentode, but a solid state pentode. The Teledyne FETRON was kind of a piece of electric fecal matter. The JFETs were doped crystal imbedded into a quasi planar substrate mess with the passive parts soldered onto SMD pads on the substrate connected with gold wire leads. It was a nice idea, but by the time the process was perfected with a reliable monolithic design there were not really very many devices left still using tubes where it would be beneficial. Western Electric made their version called an HIN. Good luck finding one of those. The phone company burned up millions of both of them, just by using them. Today we can still find MOSFETs that will handle 400,600,1000 volts but not any JFETs. Not anymore. If you have an old Phillips ECG or an NTE or one of the big old master cross reference simple semicon books you can find them, back in the 1970s, 1980s catalogs & books. NTE parts were and still are very expensive. Old NTE & old Phillips ECG catalogs are going to have the most common active electronic repair parts in them. A 1970s ECG catalog is going to have an awful lot of CRT TV transistors & ICs and lots of CB radio transistors & IC chips in it. By the 1990s lots of VCR parts. Who uses any of that stuff now?
Topic: Fetron the Unknown (Read 17111 times)