Tube Testers and Classic Electronic Test Gear
By Alan Douglas
REVIEWED BY RAY BINTLIFF
The title says it all. Tube testers are the major topic of Alan Douglas' new book. But, he covers other types of test equipment as well. The book contains a total of 166 pages, and Part I, with just over 100 pages, is devoted to tube testers. Other test equipment is covered in Parts II and III.
Douglas makes a convincing case for acquiring old vacuum tube test equipment, either from a pure collecting standpoint or on the basis of its utility. With the advent of smaller and lighter solid-state test equipment, commercial users of test equipment disposed of their vacuum tube equipment. And as a visit to a Ham or old-radio flea market will attest, there is a lot of good functional test equipment for sale at reasonable prices. If you are a test equipment freak -- and I confess that I am a member of that tribe you may want to preserve some of these classic items just as you would an old radio.
Part I Tube Testers
The stated purpose of Alan's book is "to give an overview of the [test equipment] field." He does that and more in his coverage of tube testers. As in his Radio Manufacturers of the 1920's series, he utilizes illustrations and advertisements taken from old radio publications to portray the history of tube testers.
To this historical coverage he has added useful information about tube tester basics. He describes the differences between emission type testers and mutual-conductance models. He also offers some helpful hints regarding the purchase of a tube tester that can be useful, especially to the first-time buyer.
Tube Testers and Classic Electronic Test Gear cover
The section dealing with the Hickok circuit and calibration should be of interest to the technically inclined reader, but may be challenging to the less experienced technician. The same is true of the coverage of curve tracers instruments used to display the operating characteristics of vacuum tubes. The point is that this part of the book is more than just a tube tester primer.
Thirty manufacturers of tube testers are included. Some will be familiar, such as B&K, EICO, Heathkit, Hickok and Supreme. Others, with less than household names, include AVO, an English manufacturer; Bettorf & Funke, makers of a German military model; and the Anko Manufacturing Co. of Milwaukee that produced the "Teletest" model in 1952. The Teletest used 30-plus tube sockets to test TV tubes, including picture tubes, and thus did not require a tube chart or switches.
Early tube testers from Hoyt, Jewel and Sterling are covered. A.R.C. readers may recall that the Hoyt Electrical Instrument Works was the subject of an article in the July 1997 issue. Jewel and Sterling are well known names from the early days of radio. In addition to the commercial tube testers, Douglas provides excellent coverage of testers built for the military.
The complexity level of the described tube testers runs from the low-end filament testers through the low-cost emission testers and up to the multi-featured mutual-conductance testers.
No matter what your degree of technical skill may be, you will find something of interest in this part of the book. Likewise, readers contemplating the purchase of a tube tester will find useful guidance and advice.
Part II Component Measurement
Part II covers those instruments used for testing components and circuits: Volt-Ohmmeters (VOMs), Vacuum tube voltmeters (VTVMs), Q-meters, grid- dip meters and bridges.
VOMs have been around for a long time, but the model that usually springs to mind when we think of VOMs is the famous Simpson 260. The history of its maker, Simpson Electric, is covered nicely. Representative VOMs from other manufacturers are illustrated.
As part of the VOM section, Alan covers a few of the once-popular set analyzers. While these analyzers are of historical interest, they have little practical value today. In a historical vein, he describes the origins of the D'Arsonval meter and supplements it with some early drawings and photographs.
Alan relates some of the VTVM's history and notes that John F. Rider is to be credited with producing the first "modern" VTVM, the "Voltohmyst." After Rider sold his test equipment line to RCA, the voltohmyst was heavily marketed by RCA. There were many knock-offs based on the Rider/RCA design including the popular Heathkit versions.
Ballantine, Hewlett-Packard and General Radio laboratory-quality VTVMs are included in the book.
Q-meters are laboratory instruments used mainly for design and development work, and not commonly used as radio service instruments. But their history and that of the Boonton Radio Corporation make good reading. Alan's book includes some interesting photographs of the Boonton operation, circa 1935. A picture of the more affordable Heathkit QM-1 Q-meter is shown in the book.
Like Q-meters, grid-dip meters are not commonly used in radio servicing, but find greater use in the Ham Radio field. Douglas describes a number of GDMs including the much sought after Millen version. It might have been helpful to the uninitiated if Alan had explained the GDM's principle of operation. However, the reproduced advertisement for the Heathkit "dipper" does list some uses for the instrument.
The book covers a host of capacitance and inductance bridges, many of them of laboratory quality. For the typical radio collector, the capacitance bridge is probably of the greatest interest. Just about every manufacturer of capacitors also produced capacitor testers that used the bridge-circuit principle. But the Sprague "Tel-Ohmike" models seem to be the most versatile. These Sprague testers utilize both a tuning eye tube and an analog meter. Alan describes these models along with others.
This section of the book also provides practical information regarding the measurement of capacitor leakage and the reforming of electrolytic capacitors. Also mentioned is the equivalent series resistance (ESR) test to determine the condition of electrolytic capacitors. This test method was described in greater detail by Alan in the May 1998 issue of A.R.C.
For the hard core test equipment junkies, there are photographs and descriptions of several laboratory grade bridges.
Substitution boxes are also included in this section. Although these handy devices are not truly measuring devices, they are certainly worthy of mention.
Part III Signal Measurement
Part III covers signal generators, signal tracers and oscilloscopes. Along with VOMs and tube testers, these test instruments are the work horses of radio servicing.
Vacuum tube type, radio frequency, signal generators came on the scene in the early 1920s. For example, RCA Victor Service Notes from that period include a schematic diagram for constructing a modulated oscillator capable of covering the broadcast band. A Radio Marine Corporation of America unit, circa 1929, is shown in Alan's book.
A short tutorial and history of RF signal generators appears at the start of this section and is followed by several pages of illustrations. The RF signal generators included in Part III extend from bare bones units to some elegant models made by Hewlett Packard, General Radio and other manufacturers. Good coverage of military units is included with special attention to the URM-25.
Douglas notes that while most RF signal generators also provide an audio signal in some form, dedicated AF signal generators provide a number of features that are indispensable for audio work. He also describes how Hewlett Packard outgunned General Radio with its R-C type audio signal generators. In addition, the book touches briefly on RF and AF sweep generators.
The merits of signal injection versus signal tracing for radio troubleshooting have been debated over the years. Alan expresses the belief that signal generators won the battle. In any event, a signal tracer is still a handy instrument to have on the bench. The book contains photographs of two representative units from EICO. The book describes the Rider "Chanalyst," the first multi-channel signal tracer, as well as similar units from Meissner, Hickok and Superior. Also covered is a related test instrument the field strength meter.
The book closes with a section dedicated to the oscilloscope. Alan provides a brief history of the development of the oscilloscope. And we learn that General Radio did much of the pioneering work that produced a practical oscilloscope but later lost its market share to DuMont. Included is a reproduction of a page from a General Radio catalog supplement dated May 1931 that shows an early 'scope.
Alan goes on to explain how Tektronix revolutionized the oscilloscope field in the mid-1950s. Tektronix and DuMont models are covered in detail and lists of models, along with prices and model years, are included. Other scopes included in this section are a Heathkit "Professional," an RCA TMV-122B, circa 1935, and a Waterman "Pocketscope." I wish he had included the National unit with the one-inch CRT.
How would you write a book about vacuum tube test equipment? Think about the number of basic instruments and then multiply that by the number of manufacturers and models. The result is overwhelming. No wonder Douglas' goal was to provide "an overview."
Readers may question why a particular piece of equipment was included, or not included. Alan does state that he has favored some laboratory-grade equipment over commercial grade testers. But authors must make these choices. Overall, Alan's selections and his degree of coverage for each test equipment type seem well done.
The book has some production problems. A few blank pages make it difficult to tell whether the printer failed to print both sides of the page or if the page was left blank intentionally. If the blank pages are meant to be filler pages, then the inclusion of a page number or some logo would make the publisher's intent clear.
Another nice touch would have been to key some of the illustrations to the text.
Overlooking these problems and considering content, collectors should find this book informative and useful. It contains many illustrations to supplement the text, and the quality of these black and white illustrations is good, except for the schematic of a B&K tube tester. Obviously, the original blueprint was equally illegible. The book's cover is printed in color, but has a lackluster quality.
Tube Testers and Classic Electronic Test Gear is published by Sonoran Publishing, LLC, Chandler, AZ. Priced at $25.95, it is softbound in an 81/2" x 11" format. Copies may be ordered from A.R.C. and other A.R.C. advertisers. Be sure to check suppliers for shipping information.
(Ray Bintliff, 2 Powder Horn Lane, Acton, MA 01720)