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What's Your EQ?
January 1962 Radio-Electronics

January 1962 Radio-Electronics

January 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.

As I write this, it is the day before Thanksgiving. While awaiting the 5:00 whistle to blow so you can go home for a four-day weekend, take a shot at these three circuit puzzlers from a 1962 issue of Radio-Electronics magazine. Due to the published era, the first problem is probably unsolvable today by all but two or three people on Earth. Jack Darr was the TV troubleshooter guy for the publication, and his contributions were always the hardest to solve. The composite analog signal format which comprised a standard color television signal was utterly amazing. Receiver circuits which parsed and processed those signals were more amazing, particularly given the opportunity between the broadcast antenna and the TV to confound the signal. Ambient noise and multipath were the two most prominent offenders. "A Puzzle in Fours" is a relatively simple matter of writing equations to solve multiple unknowns. "High-Output Black Box" requires a bit more cogitation, but count on other than just resistors inside, with accompanying phase shifts. Gobble, gobble.

What's Your EQ?

What's Your EQ (Electronics Quotient) ?, January 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 14 St., New York, N. Y.

Zenith 17 B20 Garbled Display - RF CafeZenith 17 B20

The picture looked like the photo. This is the best that could be done. The horizontal hold would get the picture up this far; then it would flip rapidly over to the same thing, leaning the other way! This picture would be quite stable like this, holding very well. It would not come up and lock in at all.

Horizontal afc? A check of the tube showed it OK. Horizontal oscillator, afc and horizontal control tubes, OK. All parts in afc circuit good. All dc voltages OK.

Is this trouble in the horizontal afc/oscillator circuit or not?

  - Jack Darr

Hint: Check pulses on plates of afc.

 

A Puzzle in Fours - RF CafeA Puzzle in Fours

Find the values of R1 and R2 from the information given on the schematic.

  - Don J. Ponce, Jr.

 

High-Output Black Box

This Black Box has four terminals. It contains a number of resistors and capacitors so connected that, for a specified frequency or band of frequencies, the output voltage exceeds the input voltage. The box contains nothing but resistors and capacitors and the necessary wire to connect them. How do you figure this is possible?

  - Richard L. Koelker

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

Fig. 2 - Blurry mess found on pin 3, cathode, of 6CN7. After repair, these looked like Fig. 2, but 180° out of phase, of course.

Fig. 1 - Horizontal pulses from flyback, found on plate, pin 2 of 6CN7 horizontal afc.

Zenith 17B20

The Fringe-Lock control, a 5-meg unit in first and second grids of 6BD8 noise-clipper/ agc, open. This allowed the sync clipper section of this tube to run wild. Figs. 1 and 2 show the pulses found on the plate (pin 2) and cathode (pin 3) of the 6CN7 afc. The pulses from the horizontal discharge tube on pin 2 are OK, but the pulses from the 6BU8 are quite a mess. Replace control.

 

Puzzle in Fours

High Output Black Box - RF cafeSince the sum of the power dissipated by all three resistors must equal the total power supplied:

IE1 + P2 + R3I2 = PT

Since E1 is equal to 4, as is R3, we substitute and rearrange:

4I2 + 4I + 4 = 7

or: 4I2 + 4I - 3 = 0

Solving the quadratic:

(2I + 3) (2I - 1) = 0

Equating each factor to zero, we have 2I + 3 = 0 and 2I - 1 = 0

then: 2I = -3, so 2I = 1, and I =-3/2, finally I = 1/2 amp.

The negative current has no meaning to us in this problem, so we use 1/2 ampere, and find that it gives correct results. R1 equals 8 ohms and R2 equals 16 ohms.

 

sum of the power dissipated by all three resistors - RF CafeHigh Output Black Box

The gain through a simple, unloaded R - C integrator or differentiator (Fig. 1) varies with the phase shift through the network. It varies with the cosine of the phase angle, being 1 at 0°, 0.866 at 30°,0.500 at 60° and 0 at 90°. If two or more units with the same phase shift are cascaded, and the impedance of connected networks so chosen that they do not load one another, the phase shift through the cascaded networks is the sum of the individual phase shifts and the network gain is the product of the gains of the individual networks. Therefore, a "Black Box" can be connected as in Fig. 2 to obtain a voltage approximately 1.3 times the input volt-age at the frequency for which it is de-signed. The three 30° sections cascaded have a total phase shift of 90° and an overall gain of 0.8663, or approximately 0.65. (The theoretical maximum gain of such a network is 2.) Such "amplifying" R - C networks may be used to construct cathode-follower oscillators."

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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.

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