Note: Some documents formerly listed here are now only listed in the "Tech's Filing Cabinet".
Various documents that reside on the One Electron web site:
National HRO Communications Receiver - Instruction Manual for original (1935) HRO ham receiver plus a reprint of Jan.1935 QST article about the receiver. 20 pages. 2.3Mb pdf format.
"California 220,000-Volt - 1100-Mile - 1,500,000 Kw. Transmission Bus" an article from Transactions of the American Institute of Electrical Engineers (AIEE) by R.W. Sorensen, H.H. Cox & G.E. Armstrong, 1919. Discusses long-distance transmission line issues, as well as problem of integrating 50 cycle power systems in the Los Angeles area with the rest of the bus. 32 pages, 1.8Mb pdf format.
Radio Shack touting Ampex - An advertisement from the March, 1952 Electronics magazine. The model 400A had just been announced. Note the 307 instrument recorder (versions of the 300) and the 375 Capstan Motor Amplifier in the lower left corner. 1 page, 993K gif image.
Gonzo Cathode Follower OTL Amp from 1951 - An article from the Nov. 1951 issue of Electronics magazine. Massive overkill design for 6 watt output. Check out the four 872A rectifiers in the power supply! There are comparisons against various output transformers. Also here are letters to the editor on this article. Article: 4 pages 621K pdf format, Replies: 2 pages 182K pdf format.
Getter Materials for Electron Tubes - An article from Oct. 1950 Electronics. Everything you wanted to know about getters. Extensive bibliography. 7 pages, 1.3Mb pdf format.
What Cathode is Best for the Job? - An article from April 1959 Electronic Industries about all the trade-offs in cathode design and material. More than you could possibly want to know. 6 pages, 1522K pdf format
The Material and Shapes of Vacuum Tube Heaters - an article from Dec. 1961 Electronic Industries that summarizes heater construction. 5 pages, 916K pdf format.
Tubes or Transistors? - An article from April 1959 Electronic Industries that gently reminds readers of the benefits of tubes in the midst of the pro-transistor frenzy. 6 pages, 891K pdf format.
Developments in Trustworthy Valve Techniques - An article from IT&T's Sept. 1954 Electrical Communication about the testing and design of reliable tubes (as we would say in America). Note that Standard Telephones and Cables Ltd., the authors' employer, was a subsidiary of IT&T. 17 pages, 2840K pdf format.
Heathkit RC-1 Radiation Counter (Geiger Counter) Partial Manual - Everything except construction steps for the Heathkit 1956 Geiger Counter. Interesting mix of tube and solid-state technology, 1.0 Mbyte pdf format.
Recent Developments in Miniature Tubes - an article by B. Salzberg and D.G. Burnside that originally appeared in the Proceedings of the I.R.E., Oct. 1935, and scanned from Electron Tubes, Vol. I by RCA. This explains the development of the first acorn tubes: 954 and 955. 16 pages, 1.3 Mbyte pdf format.
Development and Production of the New Miniature Battery Tubes - an article by N.R. Smith and A.H. Schooley the originally appeared in the RCA Review, April, 1940, and scanned from Electron Tubes, Vol. I by RCA. This explains the development of the first 7-pin miniature tubes: the 1R5,1T4, 1S4, and 1S5. 7 pages, 849 Kbyte pdf format.
Ampex Ultra High Fidelity Tape Recorders - a 16-page brochure from the early 1950s that covers the model 300 and 400 Ampex tape recorders, as well as their variants. Explains to the semi-technical decision-maker why Ampex is so good. Due to the multi-color, detailed presentation, the file is large (6.8Mbyte pdf).
Ampex AG-440 Brochure, Jan. 1967 - covers the original AG-440-1, -2, -3, and -4 tape recorders as well as the AG445 playback-only version. (3.2Mbyte pdf)
Ampex AG-440-8 Brochure, Dec. 1967 - describes the first AG-440 8-track. References previous AG-440 brochure. (627K pdf)
Ampex AG-440 price schedule A159, Feb. 1967. Covers AG-440-1, -2, -3, -4, AG-445 variants, and accessories. (732K pdf)
Fairchild 670 Compressor - the classic 1950's unit. This schematic was supplied by Chris Jenrick, and was recreated from the original.
Ampex AG-300 Tape Recorder Brochure, April 1967. Describes the solid-state version of the venerable 300 (2Mbyte pdf)..
"Operation Characteristics of the Type 6L7" - Ken-Rad Engineering Bulletin CEB 36-6 (April 1, 1936) describing the 6L7 pentagrid mixer tube. (17 pages, 890K pdf)
"Class C Amplifier Calculations With the Aid of Constant-Current Characteristics" - 1945 paper by Eimac describing how to design class-C triode amplifiers using constant-current curves. (4 pages, 634K pdf)
"Vacuum Tube Ratings" - 1945 paper by Eimac explaining how to interpret maximum ratings of their power triodes. (4 pages, 452K pdf)
"Tube Filament and Heater Characteristics" - an article by Cecil E. Haller that first appeared in the July 1944 issue of Electronics magazine. (6 pages, 529K pdf)
"Secondary Electron Radiation" - an article by J.H. Owen Harries that first appeared in the Sept. 1944 issue of Electronics magazine. Includes a description by the author of his development of the "Critical-distance Tetrode" (i.e. Beam Tetrode) in 1931. (9 pages, 939Kb pdf)
"The 6BN6 Gated Beam Tube" - two articles from the 1949 National Electronics Conference introducing the 6BN6. This tube was designed by General Electric and Zenith Radio Corp as a way for Zenith to get around the RCA FM patents.
"Beam Power Tubes" - classic 1938 article by O.H. Schade of RCA on the requirements of audio amplifier tubes and how the beam power tube (6L6) is the best solution. Even if you are only into triodes, this is worth a read, since it combines a good "requirements document" for audio amplifiers along with the electron physics of how beam power tubes operate. Originally published in Proc. of the I.R.E., Feb. 1938, this was scanned from the RCA "Electron Tubes Vol. I (1935-1941)", published by RCA Review in 1949. (45 pages, 3.8 Mb pdf)
"The 6L6 Beam Power Amplifier" - Ken-Rad Engineering Bulletin CEB 36-8 (April 27, 1936) describing the application of the 6L6 beam power tube. Lots of interesting power and distortion curves. (23 pages, 1.2 Mbyte pdf)
Amplification Factor Chart - an Electronics Reference Sheet (from Electronics magazine in the late 1930s) giving a good way to calculate triode mu. Now go design some tubes! (238K pdf)
"Effects of AC Plate Voltages on Tube Performance" - An article from the Sylvania Engineering Information Service, Vol. 1, No. 10 (May 1954) about minimizing the problem of "plate back emission". Important if you are designing AC servo amps with tubes. (550K pdf)
Series String Tubes - a collection of three articles by Sylvania and GE from 1954 and 1956 about the issues of connecting tube heaters in series in TV sets. (1.3 Mb pdf)
6AS7-G Low Mu Twin Power Triode in Audio Service - Application Note from the Oct.-Dec. 1947 RCA Ham Tips magazine. Often-overlooked factors when using the 6AS7G as an audio power amplifier. (182K png)
How to Build a "Junkbox" Electric Guitar - an article in the Nov. 1939 Radio-Craft magazine by Frank E. Chambers, W9BMN on building a guitar amp using push-pull '45s. Also shows how to build the magnetic pickup. (362K pdf)
The 2B6 - A Duplex Triode - an article in the Sept. 1933 Radio-Craft by L. Van Der Mel about the class A2 triode as an output stage. (553K pdf)
Quality in Audio Amplifiers - an article in the Sept. 1933 Radio-Craft by W.H. Hollister about amplifiers using the 2B6. Shows a bi-amp system, too. (320K pdf)
Designing and Constructing Direct-Coupled A.F. Amplifiers, Part I and Part II - articles in the August and September1933 issues of Radio-Craft by L.M.Barcus showing various direct-coupled circuits (359K, 443K pdfs)
Engineering Features of the UX-245 - an article in the July 1929 Radio Broadcast by F.H. Engel on how to best use the new type '45 power triode.(360K pdf)
A High-Power Output Tube - The 250 - an article in the March 1929 Radio Broadcast by K.S. Weaver on the design issues that led to the development of the '50. (418K pdf)
Note: the following articles (in brown) were scanned from magazines borrowed from Mark Rauber of Gardnerville, Nevada:
A New Electron Tube - an article by Sylvan Harris in the July 1927 Radio News about GE's development of the "Shielded-Grid" tetrode - which evolved into the RF tetrode and pentode. (404K pdf)
The Shielded-Grid Tube At Last Arrives - an article in the January 1928 Radio News about the first American implementation of the shielded-grid (i.e.screen grid) tetrode, the '22. (304K pdf)
A New Rectifier Tube for "A-B-C" Power Units - an article in the Oct. 1926 Radio News about the Raytheon "BH" gas rectifier. (396K pdf)
The Raytheon "A" Rectifier - an article by James Millen in the August 1927 Radio News about the Raytheon low-voltage electrolytic rectifier, used in "A-B Eliminators". Not mentioned in the article is that these sometime exploded, earning the nick-name "Baby Eliminator" within Raytheon, due to a miscarriage that supposedly resulted from an explosion. (see pages 44-45 of The Creative Ordeal by Otto J. Scott for more details). (558K pdf)
What Is the Best Loud Speaker, and Why? - an article by H. Winfield Secor in the March 1927 Radio News about speaker theory for the radio listener. Check out the 20 foot Orthophonic phonograph on the first page! (908K pdf)
A Simple Roll-Type Loud Speaker - an article by E.M. Yarbrough in the July 1927 Radio News. Remember the lineanum tweeter? This looks like the same thing. (215K pdf)
A Three-Foot Roll-Type Loudspeaker - an article by Clyde J. Fitch in the February 1927 Radio News on another lineanum-type speaker (252K pdf)
Chemical Condensers of Large Capacity - an article by Clyde J. Fitch in the August 1926 Radio News. How to build your own electrolytic capacitors. (394K pdf)
Vacuum Tubes and Their Uses - an article by M.L. Muhleman in the August 1926 Radio News. Good survey of American receiving tubes circa 1926. (1.3Meg pdf)
Tubes Within Tubes - an article by G.C.B. Rowe from the July 1926 Radio News on Dr. Siegmund Loewe's multi-section tubes, from Germany. These were truly the first integrated circuits, since not only triodes, but passive components were enclosed in the vacuum tube. (558K pdf)
New Radio Devices of Fixed Precision - an article from the July 1926 Radio News on some more of Dr. Loewe's inventions: metal-film resistors and visually-indicating quartz crystals. These crystal indicators were used by the Germans in WW2 to calibrate their field and aircraft radios. (463K pdf)
The following series of articles written by Sylvan Harris give a good overview of 1920's amplifier design. Unfortunately, not all sections of this series are available.
"MotorBoating," What It Is and Why - an article by O.D. Westcott in the August 1927 Radio News on the sporting proclivity of resistance-coupled amplifiers. (416K pdf)
Some Aspects of High Quality Reproduction - two articles by Paul Traugott on what contributes
to high quality reproduction in radios:
Part I - the RF and detector contributions - July 1927 Radio News (318K pdf)
Part II - the AF amplifier contribution - August 1927 Radio News (289K pdf)
Advancements in R.F. Stabilizing Systems - an article in the May 1927 Radio News about methods in stabilizing triode RF amplifiers in radios - a problem that would become moot within a few months with the introduction of the screen-grid tube. (314K pdf)
The Browning Drake Receiver - several articles on a popular radio receiver design of the 1920s - a neutralized triode RF amplifer followed by a triode regenerative detector, then two or three audio amplifier stages.
An A.C. Phonograph Amplifier - an article by James Millen in the Jan. 1928 Radio News about constructing a high-quality phonograph amplifer using push-pull '10s. (1.1Mb pdf)
Some high-end hi-fi schematics:
Evolution of Frequency Modulation - an article by Edwin H. Armstrong in the Dec. 1940 issue of Electrical Engineering, the journal of the American Institute of Electrical Engineers (A.I.E.E). A good overview of the growth of FM broadcasting by the inventor himself. 3.0 Mb pdf.
A Receiver for Frequency Modulation - an article by J.R. Day of the Marcellus Hartley Laboratories, Columbia University (where Armstrong developed FM) on "The first published data for the construction of an f-m receiver". From the June 1939 issue of Electronics. 871Kb pdf.
A High Efficiency - High Quality Audio Power Amplifier - a paper by Alexander B. Bereskin given at the 1954 IRE National Convention about class-B amplifier design. Lots of circuits and ideas. 559Kb pdf.
System Design Factors for Audio Amplifiers - a paper by M.V. Kiebert, Jr given at the 1954 IRE National Convention. Detailed analysis of push-pull amplifier design. 902Kb pdf.
Active Bandpass Filter has sharp cut-off - an article from the Aug. 15, 1958 Electronics magazine by J. Ross Macdonald about a tube-type 7th-order high and low pass filter. Offers ideas for active cross-overs as well as interesting techniques for reducing distortion by reducing heater voltgage. 611K pdf.
Acrosound Transformer catalog from 1955- has interesting push-pull amplifier circuits, too. 1.5 Mb pdf
A bunch of H.H. Scott "Service Bulletins". These contain alignment, diagnostic info and schematics:
Some more vintage Hi-Fi service info, schematics:
Early FM articles:
"The Williamson Amplifier", reprints from Wireless World magazine on the Williamson amplifier. The articles range from 1947 to 1952. This is the original British booklet, not the reprint by Old Colony, so the advertisements are the original British ones. 3.4Mbyte pdf
National HRO-5A1 reciever manual - This is the last of the traditional HRO receivers, built during 1945 and 1946. 2.1Mbyte pdf
Williamson Amplifier Heathkit manuals
- These are scans of the entire construction manuals of three classic
"Williamson Amplifiers", sold by Heathkit in the mid 1950s.
Heathkit set the standard for completeness of their manuals, and
you can see that here.
Newark Radio 1937 Ham Radio Flyer - This is an 8-page catalog from Newark Radio in Chicago geared for ham radio customers. It gives a nice snapshot of the radio art in 1937. 8.2Mb pdf
Note: If you have problems printing the large gif or jpeg files (can't fit the image on a page), a graphics editor that can automatically resize the image to the page should be used. IrfanView is a freeware program that does this very well. See http://www.irfanview.com