May 1961 Radio-Electronics
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Electronics,
published 1930-1988. All copyrights hereby acknowledged.
magazine folks who thought up the May 1961 issue's "What's you EQ?" (Electronics
were in rare form; they called it "a department of mental calisthenics." The
first two of three were real posers, both with multiple correct answers. Readers
obliged the challenge with many proposed solutions, so many that the June and
July issues were required for providing enough print space. The third, while
fundamentally simple, can throw you for a loop if you overthink the problem.
I didn't come up with their solution. Going with the not overthinking approach,
mine suggested that there is nothing in the black box (i.e., open circuit) and
that the internal resistance of the voltmeter was 10 Ω, which would cause
1 A to be drawn from the 10 V source while registering 0 W on the wattmeter.
That's the solution with an absolute minimum of thought. None of the readers -
at least those who wrote in - came up with that.
What's Your EQ?
We are starting this month a department of mental calisthenics - an opportunity
for you to see just how fast your brain can turn corners. So that everybody can
have a chance, the exercises are graded into three groups. The first will be practically
on the engineering level, the second something for the good practicing TV technician
and the third for the beginner.
Next month we will publish possible solutions to the first two questions, plus
the answer to the third.
Since the first two problems will probably have more than one good solution -
there are more ways than one to lick a design problem, and a single set of symptoms
in a TV set may have more than one cause - we are asking our readers to send in
what they consider the best solutions for the first two. Mail your answer to Puzzle
Editor, Radio-Electronics, 154 W. 14th St., New York 11, N.Y.
Radio-Electronics invites its readers to send in their own original brain-teasers.
We will pay $10 for each one used.
Two photo-relay circuits are to be used to maintain the temperature of an oven
between the limits of 450° and 500°. The phototubes are illuminated through two
openings in the temperature-indicating meter of the oven as shown in the drawing.
The oven is heated by a 117-volt heating element which should turn off when the
meter pointer blocks the opening at 500°, and turn on again when the pointer
drops back to 450° The 50° dead zone is used to limit the number of relay
operations per hour (which would be much higher in a single phototube system). What
circuit arrangement will provide the desired temperature regulation without requiring
any manual controls except an on-off switch in the power line? The circuit must
work from a "cold" start when the pointer of the meter is still below the 450°
level. - Ed Bukstein
Service Stinker No.1
Symptoms: No picture. Slight hum in sound, resistor R1 burns out immediately.
1/2-watt size is correct; other sets work with this value. Dc voltages normal.
No shorts to ground. Tubes all replaced.
Question: What is burning R1 out in such a hurry? - Jack Darr
This is one of the classics among the simple problems. It requires knowledge
of only the most fundamental laws, and can have but one answer. Yet it is very tricky
for the person who is not looking for that one answer.
A black box is connected to a power source that supplies it with 10 volts and
1 ampere, as indicated by a conventional voltmeter and ammeter. Yet an equally conventional
wattmeter also connected across the input of the black box shows that no power is
being supplied to the load. What is in the black box?
Quizzes from vintage electronics magazines such as Popular
Electronics, Electronics-World, QST, and Radio News
were published over the years - some really simple and others not so simple. Robert P. Balin
created most of the quizzes for Popular Electronics. This is a listing
of all I have posted thus far.
- RF Cafe Quiz #71:
Tech Headlines for Week of 3/13/2023
- RF Cafe Quiz #70:
RF Filter Basics
- RF Cafe Quiz #69:
- RF Cafe Quiz #68:
RF & Analog Company Mergers & Acquisitions in 2017
- RF Cafe Quiz #67:
RF & Microwave Company Name Change History
- RF Cafe Quiz #66:
Spectrum and Network Measurements
- RF Cafe Quiz #65:
Troubleshooting & Repairing Commercial Electrical Equipment
- RF Cafe Quiz #64:
Space-Time Adaptive Processing for Radar
- RF Cafe Quiz #63:
Envelope Tracking Power Amplifiers
- RF Cafe Quiz #62:
Stimson's Introduction to Airborne Radar
- RF Cafe Quiz #61:
Practical Microwave Circuits
- RF Cafe Quiz #60:
Ten Essential Skills for Electrical Engineers
- RF Cafe Quiz #59:
Microwave Circulator Design
- RF Cafe Quiz #58:
Microwave and Millimeter-Wave Electronic Packaging
- RF Cafe Quiz #57:
Frequency-Agile Antennas for Wireless Communications
- RF Cafe Quiz #56:
and Electron Tube Equipment
- RF Cafe Quiz #55:
- RF Cafe Quiz #54:
Microwave Mixer Technology and Applications
- RF Cafe Quiz #53:
Chipless RFID Reader Architecture
- RF Cafe Quiz #52:
RF and Microwave Power Amplifiers
- RF Cafe Quiz #51:
Antennas and Site Engineering for Mobile Radio Networks
- RF Cafe Quiz #50:
Microstrip Lines and Slotlines
- RF Cafe Quiz #49:
High-Frequency Integrated Circuits
- RF Cafe Quiz #48:
Introduction to Infrared and Electro-Optical Systems
- RF Cafe Quiz #47:
LCP for Microwave Packages and Modules
- RF Cafe Quiz #46:
RF, Microwave, and Millimeter-Wave Components
- RF Cafe Quiz #45:
Dielectric and Thermal Properties of Materials at Microwave Frequencies
- RF Cafe Quiz #44:
Monopulse Principles and Techniques
- RF Cafe Quiz #43:
- RF Cafe Quiz #42: The Micro-Doppler
Effect in Radar
- RF Cafe Quiz #41: Introduction
to RF Design Using EM Simulators
- RF Cafe Quiz #40: Introduction
to Antenna Analysis Using EM Simulation
- RF Cafe Quiz #39: Emerging
Wireless Technologies and the Future Mobile Internet
- RF Cafe Quiz #38: Klystrons,
Traveling Wave Tubes, Magnetrons, Crossed-Field Amplifiers, and Gyrotrons
- RF Cafe Quiz #37: Component
Reliability for Electronic Systems
- RF Cafe Quiz #36: Advanced
- RF Cafe Quiz #35: Frequency
Synthesizers: Concept to Product
- RF Cafe Quiz #34: Multi-Gigabit
Microwave and Millimeter-Wave Wireless Communications
- RF Cafe Quiz #33: Battlespace
Technologies: Network-Enabled Information Dominance
- RF Cafe Quiz #32: Modern Communications
Receiver Design and Technology
- RF Cafe Quiz #31: Quantum
Mechanics of Nanostructures
- RF Cafe Quiz #30: OFDMA System
Analysis and Design
- RF Cafe Quiz #29: Cognitive
- RF Cafe Quiz #28: Human-Centered
- RF Cafe Quiz #27: Remarkable
- RF Cafe Quiz #26: Substrate
Noise Coupling in Analog/RF Circuits
- RF Cafe Quiz #25: Component
Reliability for Electronic Systems
- RF Cafe Quiz #24: Ultra Low
- RF Cafe Quiz #23: Digital
- RF Cafe Quiz #22: Remember
- RF Cafe Quiz #21: Wireless
- RF Cafe Quiz #20: Famous First
- RF Cafe Quiz #19: Basic Circuit
- RF Cafe Quiz #18: Archaic
Scientific Words & Definitions
- RF Cafe Quiz #17: Inventors &
- RF Cafe Quiz #16: Antennas
- RF Cafe Quiz #15: Numerical
- RF Cafe Quiz #14: Oscillators
- RF Cafe Quiz #13: General
- RF Cafe Quiz #12: Electronics
- RF Cafe Quiz #11: Famous Inventors &
- RF Cafe Quiz #10: A Sampling
of RF & Wireless Topics
- RF Cafe Quiz #9: A Smorgasbord
of RF Topics
- RF Cafe Quiz #8: Hallmark Decades
- RF Cafe Quiz #7: Radar Fundamentals
- RF Cafe Quiz #6: Wireless Communications
- RF Cafe Quiz #5: Company Logo
- RF Cafe Quiz #4: General RF
- RF Cafe Quiz #3: General RF/Microwave
- RF Cafe Quiz #2: General RF
- RF Cafe Quiz #1: General RF
- Vacuum Tube Quiz,
February 1961 Popular Electronics
- Kool-Keeping Kwiz, June
1970 Popular Electronics
- Find the Brightest
Bulb Quiz, April 1960 Popular Electronics
Where Do the Scientists Belong? - Feb 19, 1949 Saturday Evening Post
Mathematical Bafflers - March 1965 Mechanix Illustrated
- Op Amp Quiz -
October 1968 Popular Electronics
- Electronic "A"
Quiz - April 1968 Popular Electronics
What's Your EQ? - May 1961 Radio-Electronics
Popular Science Question Bee - February 1939 Popular Science
What is It? - A Question Bee in Photographs - June 1941 Popular Science
What's Your EQ? - June 1961 Radio-Electronics
What's Your EQ? - June 1964 Radio-Electronics
What's Your EQ? - May 1964 Radio-Electronics
What's Your EQ? - August 1963 Radio-Electronics
What's Your EQ? - May 1963 Radio-Electronics
Function Quiz - September 1969 Radio-Electronics
What's Your EQ? - March 1963 Radio-Electronics
What's Your EQ? - February 1967 Radio-Electronics
Circuit Quiz - June 1966 Radio-Electronics
What's Your EQ? - June 1966 Radio-Electronics
Mathematics Quiz - June 1969 Popular Electronics
Light Quiz - April 1964 Popular Electronics
What's Your EQ? - April 1963 Radio-Electronics
- Electronics "B" Quiz
- July 1969 Popular Electronics
- Ohm's Law Quiz
- March 1969 Popular Electronics
Antenna Quiz - November 1962 Electronics World
- Color Code Quiz
- November 1967 Popular Electronics
- August 1961 Popular Electronics
Winding Quiz - December 1964 Popular Electronics
Audiophile Quiz - November 1957 Radio-electronics
Function Quiz - March 1962 Popular Electronics
- Greek Alphabet
Quiz - December 1963 Popular Electronics
Designer's Name Quiz - July 19680 Popular Electronics
Sawtooth Sticklers Quiz - November 1960 Radio-Electronics
Radio Quiz - December 1947 Radio-Craft
Quiz - October 1955 Radio & Television News
- Electronics Physics
Quiz - March 1974 Popular Electronics
- A Baffling Quiz
- January 1968 Popular Electronics
- Electronics IQ
Quiz - May 1967 Popular Electronics
- Plug and Jack
Quiz - December 1967 Popular Electronics
Switching Quiz - October 1967 Popular Electronics
Angle Quiz - September 1967 Popular Electronics
Electronics Quiz - July 1967 Popular Electronics
- FM Radio
Quiz - April 1950 Radio & Television News
- Bridge Circuit
Quiz -December 1966 Popular Electronics
- Diode Function
Quiz - August 1965 Popular Electronics
- Diagram Quiz,
August 1966 Popular Electronics
- Quist Quiz - November
- TV Trouble Quiz,
July 1966 Popular Electronics
- Electronics History Quiz,
December 1965 Popular Electronics
- Scope-Trace Quiz,
March 1965 Popular Electronics
Circuit Analogy Quiz, April 1973
Test Your Knowledge of Semiconductors, August 1972 Popular Electronics
- Ganged Switching
Quiz, April 1972 Popular Electronics
- Lamp Brightness
Quiz, January 1969 Popular Electronics
Pattern Quiz, September 1963 Popular Electronics
Quizoo, October 1962 Popular Electronics
Photo Album Quiz, March 1963 Popular Electronics
Alphabet Quiz, May 1963 Popular Electronics
- Quiz: Resistive?
Inductive? or Capacitive?, October 1960 Popular Electronics
Matching Quiz, June 1970 Popular Electronics
Quiz, September 1961 Popular Electronics
- RC Circuit Quiz,
June 1963 Popular Electronics
- Diode Quiz, July
1961 Popular Electronics
Curves Quiz, February 1963 Popular Electronics
Numbers Quiz, December 1962 Popular Electronics
- Energy Conversion
Quiz, April 1963 Popular Electronics
- Coil Function
Quiz, June 1962 Popular Electronics
Co-Inventors Quiz - January 1965 Electronics World
"-Tron" Teasers Quiz - October 1963 Electronics World
- Polarity Quiz
- March 1968 Popular Electronics
I.Q. Quiz - October 1948 Radio & Television News
- Amplifier Quiz
Part I - February 1964 Popular Electronics
Quiz - February 1967 Popular Electronics
Frequency Quiz - September 1965 Popular Electronics
Metals Quiz - October 1964 Popular Electronics
Measurement Quiz - August 1967 Popular Electronics
Quiz, June 1966 Popular Electronics
Geometry Quiz, January 1965 Popular Electronics
Factor Quiz, November 1966 Popular Electronics
Math Quiz, November 1965 Popular Electronics
- Series Circuit
Quiz, May 1966 Popular Electronics
Quiz, March 1966 Popular Electronics
Quiz: Test Your Sales Ability - April 1947 Radio News
Analogy Quiz, November 1961 Popular Electronics
Coupling Quiz, August 1973 Popular Electronics
Analogy Quiz, August 1960 Popular Electronics
- Audio Quiz, April
1955 Popular Electronics
- Electronic Unit
Quiz, May 1962 Popular Electronics
Circuit Quiz, June 1968 Popular Electronics
on AC Circuit Theory, December 1970 Popular Electronics
Phenomena Quiz, February 1962 Popular Electronics
Geography Quiz, April 1970 Popular Electronics
Menu Quiz, August 1963 Popular Electronics
Noise Quiz, August 1962 Popular Electronics
Current Quiz, October 1963 Popular Electronics
Inventors Quiz, November 1963 Popular Electronics
- Resistor Function
Quiz, January 1962 Popular Electronics
Measurement Quiz, January 1963 Popular Electronics
Answers to What's Your EQ? (from June 1961)
Here are the answers to last month's questions. We have not been able to print
any answers from readers due to time squeeze, but, if any outstanding solutions
come in, we will run them next month.
Note: Additional responses from July 1961 at are the bottom.
1. Both relays are actuated by a decrease in light.
2. RY1 - in 500° circuit - has normally closed contacts.
3. RY2 - in 450° circuit-has normally open contacts.
4. When RY1 opens, voltage is removed from the heater and from LM1.
5. When RY2 closes, voltage is applied to the heater and to LM1.
Assume temperature is between 450° and 500°.
1. The heater and LM1 are on.
2. Light falls on both phototubes.
3. When the temperature reaches 500°, light to the phototube controlling
RY1 is blocked. RY1 opens, removing voltage from the heater and LM1.
4. The heater and LM1 remain off because RY1 is operated by a decrease in
5. As the temperature reaches 450°, the hole is blocked, RY2 pulls in
and the normally open contacts close, applying power to the heater and LM1.
Service Stinker No. 1
Although voltage measurements and current measurements show everything to be
lovely as far as dc is concerned, a scope reading taken across R1 shows something
like 300 volts peak-to-peak ripple! The exceedingly low-impedance path to ground
provided by the 10-μf capacitor causes a tremendous pulse current to flow through
the little resister, burning it out very rapidly. Cause: completely open input filter
capacitor in the power supply! Both in fact. The negative connection had opened.
This would have been cleared quickly had a scope been used on the B-plus, instead
of relying solely on dc voltage measurements.
The black box must obviously contain an intermittent contact - a chopper or vibrator,
represented in this case by an ordinary buzzer operated from its own dry-cell power
supply. In such a circuit, voltage is that of the supply when the contacts are open
and zero when it is closed. Current is, of course, zero when the contacts are open
and rises to a value limited only by the resistance of the meters in series and
the internal impedance of the source when the contacts close.
But the contacts open and close in such rapid sequence that conventional meters
cannot follow the voltage and current patterns, so take up positions between zero
and the peak values. Since the wattmeter needs both voltage and current to show
any indication, and since there is no voltage when there is current and no current
when there is voltage, it remains at zero.
More on May (from July 1961)
The Photo-Relay Circuit Problem, published on page 56 of the May issue, was to
maintain, with photo-relays, the temperature of an oven between 450 and 500°.
The pointer of a meter would block off light to the phototubes at those points.
The equipment was to work from a cold start. Fig. 1 shows the setup and the circuit
used by Ed Bukstein, who proposed the problem.
Interestingly enough, none of the solutions received at the time of writing duplicate
Bukstein's circuit exactly. The closest thing is a sort of complementary circuit
(the relays are activated by light, not by its interruption) sent by 1. S. Kerstetter
of Lansford, Pa, (Fig. 2). It depends, however, on relay B operating faster than
relay A. The heating element is connected in circuit and B locks in through its
contacts 1 and 2. Then A operates, opening the original circuit through B. The heater
circuit will now remain closed till the current through B is cut off when the phototube
is blocked at 500°. The pointer falls back to 450°, interrupts A, closes the circuit
to B through its back contacts, and the cycle starts again.
A circuit differing only in detail was proposed by electronic technician and
TV repairman J. E. Michaud of Notre-Dame-du-Lac, Quebec. Mr. Michaud also proposed
a one-relay circuit. It would, however, have required a special modification of
the meter, with a thin metal plate instead of a pointer, so that the 450° hole
would remain closed till the pointer reached the 500° point.
Kenneth A. Piletic of La Salle, Ill., uses a different approach. Both photo-tubes
are connected to the coil of relay 2 (Fig. 3). When the line switch is closed, the
element is heated through normally closed contact 1 of relay 1. At 450°, V1
goes into action, drawing current and closing circuits 1 and 2 of relay 2. The heater
is now supplied through normally open contact 1 of relay 1. Relay 2's coil is locked
in through contact 3, and relay 1's coil is locked in through its contact 1 till
ac power is turned off.
When the pointer reaches 500°, V2 draws current, dropping the voltage across
the load resistor enough to de-energize relay 2. Since relay 1 is locked in, the
heater circuit remains open till the 450° point, when relay 2 closes again.
Relay 1 is merely the cold-start device; relay 2 does all the work.
A proposal to use one relay and tube, which looks as though it should work, was
submitted by Leonard Kasday of Flushing, N. Y. The phototubes (V1, V2) (Fig. 4)
form a voltage divider across the grid of the thyratron. Resistors R1 and R4 are
so selected that V3's grid is negative enough to keep the tube from firing. When
the temperature reaches 500° V2 is cut off, its resistance rises to practically
open circuit, and V3's grid goes positive through R1, R3 and V1. The relay is pulled
in, opening the heater circuit and applying a positive bias to V3's grid on positive
half-cycles. The relay remains energized till, at 450°, V1 is cut off and V3's
control grid again goes negative, releasing the relay and turning the heater on.
Two other 1-relay circuits were proposed. They might well have operated, with
proper selection of components, but were not as clearly worked out as the one just
described. A few circuits included latching relays. (This might be the simplest
and most efficient approach.) One ingenious circuit, by John Jarvis, University
of Florida, used an ac and a dc relay for on-off control. But the great majority
of circuits included three or more relays. A few went beyond three, and one used
Fig. 1 -Mr. Bukstein's original circuit. Relays are actuated by decrease in light.
Fig. 2 - One of the simplest circuits.
Fig. 3 - Another effective solution.
Fig. 4 - This circuit uses one relay.
Most striking feature of the solutions to the photo-relay problem was the sophisticated
nature of some of the entries. At least two were presented as finished engineering
drawings, with all constants including ohm age of relay coils. One even named model
numbers and tube types - included all the information necessary to buy the parts
and construct the device. Unfortunately, some of the best prepared solutions were
not entirely clear - the author expected to be read by another relay engineer. Possibly
more than one good solution was not understood, due to unfortunate drawing and incomplete
Service Stinker No. 1
In spite of the statement: no shorts to ground, most readers decided that the
cathode capacitor was shorted. A small number - less than half a dozen - pointed
out the correct answer, an open filter capacitor, and one reader pointed out that
a shorted voice-coil winding or too-low output impedance might cause the tube to
draw enough excess current to burn out the 470-ohm resistor.
Strangely enough, the simplest puzzle produced the fewest correct answers and
the largest number of wild guesses. Readers did point out, though, that there are
two correct answers. If the power supply is dc, a chopper or vibrator can make the
meters indicate voltage and current, but no power. A perfect reactance, such as
a good capacitor, will of course produce the same result if the supply is ac.
Posted September 18, 2023