March 1973 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
By the early 1970s, many
types of vacuum tubes had already been replaced by solid state devices. A lot of the
resistance by hardline lovers of glowing tubes was beginning to accept the reality of
superior electrical characteristics of many types of germanium and silicon diodes and
transistors over tube equivalents. During my enlistment in the USAF from 1978-1982,
the vacuum tube diode used to trigger the pulse forming network for the airport
surveillance radar (ASR) circuit was replaced with a plug-in solid state replacement.
It seemed to work just as well. I don't recall ever having to replace the faulty
vacuum tube version, so I cannot attest to whether the solid state version was an
improvement. Part of the motivation for replacing tubes with solid state devices was
obsolescence of the tubes, so maybe that is why it was done.
The "fetrode" introduced here by Solitron Devices was designed to be a plug-in replacement for the
6AK5 vacuum tube,
which is a pentode amplifier. Although not specifically stated, I assume the name "fetrode"
implies it was a field effect transistor (FET).
Solitron Devices Fetrode Advertisement
• Greater longevity
• No warm up
• No filaments to burn out
• No rewiring (direct replacement)
• Internally R. F. shielded
• Low dissipation: 1.3 watts (nominal)
• Plus 500 MHz operation
• Absolute low noise/distortion
This is a 6AK5 FETRODE
a solid state device that replaces a vacuum tube for:
Stereo Tuner • Amplifiers/OSC • Citizen Band Receivers/Transmitters • Radio/TV • Many
During this introduction, you can purchase one (1) from us direct: Remit $5.00 plus
5% California state sales tax (Residents only), or if further information is required,
please fill out the following coupon.
Posted December 1, 2017