RF Cafe Homepage
Copper Mountain Technologies (VNA) - RF Cafe

What's Your EQ?
July 1966 Radio-Electronics

July 1966 Radio-Electronics

July 1966 Radio-Electronics Cover - RF Cafe[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.
What's Your EQ?, July 1966 Radio-Electronics - RF Cafe

Conducted by E. D. Clark

Three puzzlers for the student, theoretician and practical man. Simple? Double-check your answers before you say you've solved them. If you have an interesting or unusual puzzle (with an answer) send it to us. We will pay $10 for each one accepted. We're especially interested in service stinkers or engineering stumpers on actual electronic equipment. We get so many letters we can't answer individual ones, but we'll print the more interesting solutions - ones the original authors never thought of.

Answers to this month's puzzles are on page 89.

Write EQ Editor, Radio-Electronics, 154 West 14th Street, New York, N. Y. 10011.

Current-Valve Circuits - RF CafeCurrent-Valve Circuits

Circuits A and B appear to be quite different. However, they have something in common. Can you determine what ?

- Kendall Collins

 

Deflection-Coil Puzzler - RF CafeDeflection-Coil Puzzler

With a TV set operating normally, the letters shown in A appear on its screen.

(1) If the leads to the vertical-deflection coils in the yoke are reversed while the horizontal-deflection coils are correctly connected, which picture (B, C or D) appears on the screen? (2) If the leads to the horizontal - deflection coils in the yoke are reversed while vertical-deflection coils are correctly connected, which picture appears on the screen? (3) If the leads to both the vertical and horizontal deflection coils are reversed, which picture appears on the screen?

- Robert P. Balín

 

Switch-Pulse Circuit - RF CafeSwitch-Pulse Circuit

Can you determine the voltage levels and waveshape of the pulse that is produced between terminals A and B when switch S is closed for one second and then opened? The sources' internal resistances are negligible.

- Kendall Collins

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 Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Answers to What's Your Eq?

These are the answers. Puzzles are on page 43.

Current-Valve Circuits

Both circuits serve as ripple filters.

Circuit A is used in two RCA 12-inch transistor TV receivers to eliminate a large iron-core filter choke in the dc power supply.

In operation, reduced ripple applied to the base of Q1 by a network composed of R1, R2, C1 and R3. The output of Q1 is applied through R4 to the base of Q2. As a result, the base current of Q2 varies with changes in the collector current of Q1. This produces a variable voltage drop between the emitter and collector of Q2 which tends to counteract variations in the input voltage at the ripple rate. Consequently, the output voltage remains nearly constant at 30 volts.

In circuit B, a power pentode electronically regulates the output voltage as follows: A portion of the input ripple voltage is developed between the tap on the 50-ohm resistor and the tube's cathode. The reduced ripple voltage acts as a variable negative bias that is applied to the control grid through the 470K resistor. Another portion of the ripple voltage, which increases the effect of the variable negative bias, is applied to the control grid through the 0.05-μF capacitor.

The variable negative bias automatically increases and decreases the voltage drop between the tube's cathode and plate. Within certain limits, this tends to counteract changes in the input voltage and, as a result, the output voltage remains nearly constant.

 

Switch-Pulse Circuit Solution - RF CafeDeflection-Coil Puzzler

(1) C; (2) B; (3) D.

 

Switch-Pulse Circuit

Terminal A is at ground potential (zero) and terminal B varies from -9 to +9 volts. When switch is open, B is -9 volts. Closing the switch for one second changes the potential of B to +9 volts. This produces a 1-second pulse that is +9 volts above ground.  
Copper Mountain Technologies (VNA) - RF Cafe

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2025
Webmaster: Kirt Blattenberger,
   BSEE - KB3UON - AMA92498

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...

Copyright  1996 - 2026

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website: AirplanesAndRockets.com

My Daughter's Website: EquineKingdom