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What's Your EQ?
February 1962 Radio-Electronics

February 1962 Radio-Electronics

February 1962 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.

Here we are with another set of three "What's Your EQ?" circuit challenges, these from the February 1962 issue of Radio-Electronics magazine. As usual, those challenges provided by Jack Darr are the purview of television servicemen of the era. The photo shown of the problematic CRT display looks like a chest x-ray or maybe hieroglyphics in the dark corner of a cave, but evidently the artifacts are readily identifiable to an initiated few. The Forbidden Current Path circuit answer is not what I thought it would be. I maintain that whether my answer or the designer's answer is correct depends on the physical configuration of the solenoids, clapper, and contacts, as well as the material type used in the clapper arm (see my guess below). "Simple (?) AC Problem" shouldn't provide too much effort, especially for the Point A - Point B part (hint: add or subtract in terms of complex voltages, i.e, Real ± j Imaginary).

What's Your EQ?

What's Your EQ?, February 1962 Radio-Electronics - RF CafeIt's stumper time again. Here are three little beauties that will give you a run for the money. They may look simple. but double-check your answers before you say you've solved them. For those that get stuck, or think that it just can't be done, see the answers next month. If you've got an interesting or unusual answer send it to us. We are getting so many letters we can't answer individual ones, but we'll print the more interesting solutions (the ones the original authors never thought of). Also, we're in the market for puzzlers and will pay $10 and up for each one accepted. Write to EQ Editor, Radio-Electronics, 154 West 14th St .• New York, N. Y.

For answers to last month's puzzle see page 58.

Forbidden Current Path - RF CafeForbidden Current Path

In this hookup, a standard ac ringer is so hooked up that the clapper makes a good contact with a pair of contacts at each end of its swing, putting the lamp across the line. Why doesn't the lamp light when the bell is ringing and the clapper is making contact?

  - I. S. Kerstetter

 

Simple (?) AC Problem - RF CafeSimple (?) AC Problem

In the circuit shown two ac generators furnish the two voltages E1 and E2.  E1 and E2 are both 100 volts (rms)

60 cycles, but E1 leads E2 by 90°. (In other words, the potential of point A with respect to ground G reaches its maximum or peak value one quarter-cycle earlier than the potential of point B with respect to G does.)

a. What will be the voltage between points A and B, and what will be the voltage between points D and G?

b. Will it make any difference, as far as these two voltages are concerned, if the resistor and capacitor are interchanged (that is, the capacitor is placed between points A and D, and the resistor between points D and B)?

(To save calculation, the capacitive reactance of a 1-μf capacitor at 60 cycles is 2653 ohms.)

  - Walther Richier

 

Service Stinker No.3 - RF CafeService Stinker No.3

Look at the picture. What is the trouble? Horizontal phase diode out? Bad horizontal oscillator?

  - Jack Darr

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

Solutions

Forbidden Current Path Answer

When the clapper is at the end of its swing and completing the contact through the lamp, the voltage and current in the line are at zero and about to reverse direction. Therefore, both terminals of the lamp are at approximately the same voltage and the lamp does not light. (My guess was that the clapper was not in connecting with the circuit contacts long enough to light the filament long enough to be visible)

 

Simple(?) AC Problem

This looks like a deceptively simple ac circuit problem, and it is, provided one keeps very strict account of the signs or polarities of the four voltages (voltages E1, E2 and the voltage drops across R and XC). The voltage between points A and B is of course 100 x √2 = 141.42 volts. This voltage drives a current through the series connection of the resistor and the capacitor. Interchanging the two will, of course, not change the voltage between points A and B, and therefore the current will also be the same. But the voltage between points D and G will be 141.42 for the connection shown, and will be zero after the interchange!

 

Service Stinker No.3 Solution - RF CafeService Stinker No.3

Neither horizontal phase diode nor horizontal oscillator is at fault! Look at the picture. This is what a scope will show you on the B-plus line! The output electrolytic capacitor is open!

The horizontal hash feeding back into the power supply is upsetting the horizontal hold action.

Rigol DHO1000 Oscilloscope - 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

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