July 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.
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Here we go with three new
"What's Your EQ?" challenges from the July 1961 issue of Radio-Electronics
magazine. Readers submit the problems, which typically involve creating a
circuit to perform a specified function, or determining how a given circuit
works. The first of these is more of a puzzle, since the author shows
you how to go about arriving at the answer. Since incandescent light bulbs are
not overly familiar to a lot of people these days, it might be to the advantage
of pre-Millennials who grew up using them and are acquainted with their
properties. The second is an old-fashioned Black Box challenge that some readers will solve without
much trouble. The last is a service TV troubleshooting problem that almost
nobody will get, although I know a least three RF Cafe visitors who can probably
figure it out.What's Your EQ?

Answers to last month's puzzles, with comments on the May quiz, are on page 72.
We can still use brain-teasers on the engineering level - are swamped with simple
ones and TV problems. $10 will be paid for each one accepted. Address Puzzle Editor,
Radio-Electronics, 154 W. 14 St. New York 11, N.Y.
Parallel Bulb Puzzler
This is a game. It is intended, not only to mystify those of your friends familiar
with straightforward parallel circuitry, but to confound them to a point of sheer
frustration. They have before them five ordinary light bulbs of varying wattages
connected in parallel. Merely by turning each bulb into its socket, one at a time,
they are to light all four bulbs but the middle one - the 75-watter. According to
all laws this should be easy; but they find that by turning in the first bulb nothing
happens. Turn in the second bulb, all others turned out, and it glows. Now turn
in the first bulb again, and the second one goes out. Or, turn in bulbs two and
five, and both glow. Now turn in any remaining bulb and they will all go out. This
mystification will prevail until the bewildered one discovers that bulb three responds
rather peculiarly in respect to the others. Presto - with a little logic he has
it and all the bulbs but the middle one are glowing with about the same intensity.
What adds to the confusion is that the first bulb, a 40-watter, will not glow when
turned in, and this discourages the puzzler from trying the larger 75-watter which,
after all, is not to be lit. But turn it in, and there it is glowing. This, only
if all the others are turned out.
The circuitry is very simple (see figure) and need not be concealed from your
victim. It is better, in fact, to build it in a plastic box, and wire the sockets
so he can see the parallel connections.
Two questions:
1. Why does the circuit act as it does?
2. What are the values of C and L? (We can tell you that is a filter choke and
that C should be non electrolytic. )
C - ?
L - ?
R1, 2, 3, 4, 5 - Ordinary 120-volt electric light bulbs. Suggested values: R1
-40 watts; R2-15 watts; R3-75 watts; R4-25 watts; R5-15 watts.
- Martin. H. Patrick
Resistor Black-Box Puzzler
The ingenious little brain twister below is reprinted from the April 1961, issue
of Electron Bulletin, Cleveland Institute of Electronics:
Three leads, marked A, Band C, feed into a box containing three resistors. Measuring
with an ohmmeter, the resistance between A and B is 30 ohms, between Band C 40 ohms,
and between A and C 50 ohms. Draw a diagram showing how the resistors are connected,
and the resistance of each of them.
There are at least two solutions for this problem. You will find the easy one
fairly soon. Now find another hookup that will give you the same ohmages between
terminals.
What's the Trouble?
This Westinghouse V2411 chassis was lugged into the shop by the outside technician
for the condition shown in the picture: a bright horizontal bar about an inch wide
across the upper center of the raster. The technician had changed the 6EM7 vertical
oscillator output tube in the home but it had no effect. Moving the height and linearity
controls widened or narrowed the bar but did not remove it. The shop technician
made a couple of exploratory checks and announced that the trouble was a fairly
simple, though unusual, one that could have been repaired by the technician in the
home. What's the trouble?
- Wayne Lemons
Quizzes from vintage electronics magazines such as Popular
Electronics, Electronics-World, QST, Radio-Electronics,
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:
Analog &
RF Filter Basics
- RF Cafe Quiz #69:
RF
Electronics Basics
- 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:
Tube Testers
and Electron Tube Equipment
- RF Cafe Quiz #55:
Conquer
Radio Frequency
- 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:
Plasma Antennas
- 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 MEMS
- 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
Radar
- RF Cafe Quiz #28: Human-Centered
Information Fusion
- RF Cafe Quiz #27: Remarkable
Engineers
- 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
Power Bioelectronics
- RF Cafe Quiz #23: Digital
Communications Basics
- RF Cafe Quiz #22: Remember
the Basics?
- RF Cafe Quiz #21: Wireless
Standards Knowledge
- RF Cafe Quiz #20: Famous First
Names
- RF Cafe Quiz #19: Basic Circuit
Theory
- RF Cafe Quiz #18: Archaic
Scientific Words & Definitions
- RF Cafe Quiz #17: Inventors &
Their Inventions
- RF Cafe Quiz #16: Antennas
- RF Cafe Quiz #15: Numerical
Constants
- RF Cafe Quiz #14: Oscillators
- RF Cafe Quiz #13: General
Knowledge
- RF Cafe Quiz #12: Electronics
Corporations Headquarters
- RF Cafe Quiz #11: Famous Inventors &
Scientists
- 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
in Electronics
- RF Cafe Quiz #7: Radar Fundamentals
- RF Cafe Quiz #6: Wireless Communications
Fundamentals
- RF Cafe Quiz #5: Company Logo
Recognition
- RF Cafe Quiz #4: General RF
Topics
- RF Cafe Quiz #3: General RF/Microwave
Topics
- RF Cafe Quiz #2: General RF
Topics
- RF Cafe Quiz #1: General RF
Knowledge
- Vacuum Tube Quiz,
February 1961 Popular Electronics
- Kool-Keeping Kwiz, June
1970 Popular Electronics
- Find the Brightest
Bulb Quiz, April 1960 Popular Electronics
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Where Do the Scientists Belong? - Feb 19, 1949 Saturday Evening Post
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What's Your EQ? - July 1967 Radio-Electronics
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What's Your EQ? - December 1962 Radio-Electronics
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What's Your EQ? - April 1966 Radio-Electronics
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What's Your EQ? - October 1963 Radio-Electronics
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What's Your EQ? - July 1964 Radio-Electronics
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What's Your EQ? - May 1967 Radio-Electronics
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What's Your EQ? - July 1962 Radio-Electronics
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What's Your EQ? - January 1962 Radio-Electronics
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What's Your EQ? - February 1962 Radio-Electronics
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What's Your EQ? - March 1962 Radio-Electronics
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What's Your EQ? - July 1961 Radio-Electronics
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What's Your EQ? - August 1961 Radio-Electronics
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Can You Name These Strange Electronic Effects? - August 1962 Radio-Electronics
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What's Your EQ? - September 1961 Radio-Electronics
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What's Your EQ? - September 1962 Radio-Electronics
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What's Your EQ? - October 1961 Radio-Electronics
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What's Your EQ? - November 1961 Radio-Electronics
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What's Your EQ? - March 1964 Radio-Electronics
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What's Your EQ? - April 1962 Radio-Electronics
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What's Your EQ? - May 1962 Radio-Electronics
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What's Your EQ? - June 1962 Radio-Electronics
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What's Your EQ? - April 1967 Radio-Electronics
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What's Your EQ? - March 1967 Radio-Electronics
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What's Your EQ? - December 1964 Radio-Electronics
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What's Your EQ? - January 1967 Radio-Electronics
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Wanted: 50,000 Engineers - January 1953 Popular Mechanics
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What's Your EQ? - August 1964 Radio-Electronics
- Voltage Quiz
- December 1961 Popular Electronics
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What is It? - June 1941 Popular Science
- What Do You Know
About Resistors? - April 1974 Popular Electronics
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What's Your EQ? - September 1963 Radio-Electronics
- Potentiometer Quiz - September
1962 Popular Electronics
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Mathematical Bafflers - March 1965 Mechanix Illustrated
- Op Amp Quiz -
October 1968 Popular Electronics
- Electronic "A"
Quiz - April 1968 Popular Electronics
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What's Your EQ? - May 1961 Radio-Electronics
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Popular Science Question Bee - February 1939 Popular Science
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What is It? - A Question Bee in Photographs - June 1941 Popular Science
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What's Your EQ? - June 1961 Radio-Electronics
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What's Your EQ? - June 1964 Radio-Electronics
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What's Your EQ? - May 1964 Radio-Electronics
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What's Your EQ? - August 1963 Radio-Electronics
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What's Your EQ? - May 1963 Radio-Electronics
- Bridge
Function Quiz - September 1969 Radio-Electronics
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What's Your EQ? - March 1963 Radio-Electronics
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What's Your EQ? - February 1967 Radio-Electronics
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Circuit Quiz - June 1966 Radio-Electronics
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What's Your EQ? - June 1966 Radio-Electronics
- Electronics
Mathematics Quiz - June 1969 Popular Electronics
- Brightest
Light Quiz - April 1964 Popular Electronics
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What's Your EQ? - April 1963 Radio-Electronics
- Electronics "B" Quiz
- July 1969 Popular Electronics
- Ohm's Law Quiz
- March 1969 Popular Electronics
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Antenna Quiz - November 1962 Electronics World
- Color Code Quiz
- November 1967 Popular Electronics
- CapaciQuiz
- August 1961 Popular Electronics
- Transformer
Winding Quiz - December 1964 Popular Electronics
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Audiophile Quiz - November 1957 Radio-electronics
- Capacitor
Function Quiz - March 1962 Popular Electronics
- Greek Alphabet
Quiz - December 1963 Popular Electronics
- Circuit
Designer's Name Quiz - July 1968 Popular Electronics
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Sawtooth Sticklers Quiz - November 1960 Radio-Electronics
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Elementary
Radio Quiz - December 1947 Radio-Craft
- Hi-Fi
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
- Electronic
Switching Quiz - October 1967 Popular Electronics
- Electronic
Angle Quiz - September 1967 Popular Electronics
- International
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
1953 QST
- TV Trouble Quiz,
July 1966 Popular Electronics
- Electronics History Quiz,
December 1965 Popular Electronics
- Scope-Trace Quiz,
March 1965 Popular Electronics
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Electronic
Circuit Analogy Quiz, April 1973
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Test Your Knowledge of Semiconductors, August 1972 Popular Electronics
- Ganged Switching
Quiz, April 1972 Popular Electronics
- Lamp Brightness
Quiz, January 1969 Popular Electronics
- Lissajous
Pattern Quiz, September 1963 Popular Electronics
- Electronic
Quizoo, October 1962 Popular Electronics
- Electronic
Photo Album Quiz, March 1963 Popular Electronics
- Electronic
Alphabet Quiz, May 1963 Popular Electronics
- Quiz: Resistive?
Inductive? or Capacitive?, October 1960 Popular Electronics
- Vector-Circuit
Matching Quiz, June 1970 Popular Electronics
- Inductance
Quiz, September 1961 Popular Electronics
- RC Circuit Quiz,
June 1963 Popular Electronics
- Diode Quiz, July
1961 Popular Electronics
- Electronic
Curves Quiz, February 1963 Popular Electronics
- Electronic
Numbers Quiz, December 1962 Popular Electronics
- Energy Conversion
Quiz, April 1963 Popular Electronics
- Coil Function
Quiz, June 1962 Popular Electronics
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Co-Inventors Quiz - January 1965 Electronics World
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"-Tron" Teasers Quiz - October 1963 Electronics World
- Polarity Quiz
- March 1968 Popular Electronics
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Television
I.Q. Quiz - October 1948 Radio & Television News
- Amplifier Quiz
Part I - February 1964 Popular Electronics
- Semiconductor
Quiz - February 1967 Popular Electronics
- Unknown
Frequency Quiz - September 1965 Popular Electronics
- Electronics
Metals Quiz - October 1964 Popular Electronics
- Electronics
Measurement Quiz - August 1967 Popular Electronics
- Meter-Reading
Quiz, June 1966 Popular Electronics
- Electronic
Geometry Quiz, January 1965 Popular Electronics
- Electronic
Factor Quiz, November 1966 Popular Electronics
- Electronics
Math Quiz, November 1965 Popular Electronics
- Series Circuit
Quiz, May 1966 Popular Electronics
- Electrochemistry
Quiz, March 1966 Popular Electronics
- Biz
Quiz: Test Your Sales Ability - April 1947 Radio News
- Electronic
Analogy Quiz, November 1961 Popular Electronics
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Solutions
Parallel-Bulb Puzzler
The theory of operation is based on the fact that a series-resonant circuit will
pass a maximum current when it is in resonance with the frequency of the supply
source. In this case it is 60 cycles. Included in the circuit is also a resistor
in the form of a 75-watt bulb. By changing anyone of the three values - inductance,
capacitance, resistance - we upset the balance of the resonant circuit, and thereby
decrease the current.
To make this puzzler, select a filter choke of about 0.5-henry inductance and
about 60 ohms dc resistance. Set up the experiment as shown in the figure, using
any available filter choke handy. Start with a 1-μf nonelectrolytic capacitor.
Turn the 40-watt bulb into the socket. If it lights, turn it out again and add another
1-μf capacitor in parallel with the first. Continue this in small steps, adding
preferably 0.5-μf capacitors until the 40-watt bulb fails to light. Now turn
in the 75-watt bulb, and it should glow. All that remains is to connect three similar
sockets and insert in them bulbs of smaller wattages, such as a 25, 15 and another
15.
A word of caution when working on your experimental hookup: You are leading line
voltage out onto your bench - be careful! Also the capacitors store up a considerable
charge - don't think the circuit is "dead" when you pull the plug. Screw in a lamp
and discharge the capacitor. And, be sure you have only one bulb turned into its
socket when you are experimenting for the proper value of capacitance.
When you get the proper value, a single capacitor (or two if necessary to get
the correct value) may be substituted and the unit built into a box for demonstration
purposes. It is a good idea, as stated before, to make the top panel plastic and
keep the wiring in plain sight so the parallel connections can be seen plainly.
This adds greatly to the mystification.
Observe that, by taking resistance out of the resonated circuit (turning the
bulbs in decreases the resistance in the parallel bulb circuit), we do not unbalance
the resonant period greatly. On the other hand, by increasing resistance (turning
the bulbs out), we reach a definite point where the circuit suddenly drops out of
resonance.
Resistor Black-Box Puzzler
Resistance between A and B is 30 ohms; between B and C 40, and between A and
C, 50 ohms. The easy answer is at the left. But, where resistors can be hooked up
in Y-formation, they can also be hooked up in delta with the same results, as shown
at the right.
What's the Trouble
Since the set was nearly new, the shop technician decided to make a couple of
localizing checks before pulling the chassis (always a good idea). He replaced the
6EM7 vertical oscillator output again, but, as the outside technician had noted,
it did not cure the fault. Looking at the circuit, he saw that the sync separator
might be introducing the bar, or that perhaps the video amplifier was in some way
superimposing the bright bar. The shop technician localized the trouble to these
stages by pulling one tube, the 6EB8, which was both the video amplifier and the
sync separator. With the 6EB8 out, the bright bar disappeared. A new 6EB8 cured
the trouble. The original tube was checked and found to have a slight leakage from
heater to grid and heater to cathode of the triode section.
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