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What's Your EQ?
March 1966 Radio-Electronics

March 1966 Radio-Electronics

March 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?, March-1966 Radio-Electronics - RF CafeTwo puzzlers for the students, 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.

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

Answers to this month's puzzles are on page 99.

Conducted by E. D. Clark

Connections

The diagram shows a recent hi-fi annual answer to a reader's query about how to connect eight 4-ohm speakers so they could be driven properly from the 8-ohm output of an amplifier. What's wrong with it? -P. E. Sutheim

What Is It?

This is a color TV set showing a crosshatch pattern. It is? Who ever saw one looking like that? This pattern is firmly locked - no wiggle or jitter. What causes it? The set? The generator? Can you figure it out? -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

What's Your EQ? Solutions

These are the answers. Puzzles are on page 58.

Connections

Nothing is wrong, exactly, except that the cross-connections between the vertical groups of speakers are absolutely unnecessary. They affect nothing for good or for bad. Assuming speakers of identical characteristics, the potential at both ends of each cross-connection at any instant is the same. Therefore there can be no current through the wires and it matters not a whit whether they are present or absent.

Actually there are two ways of accomplishing the same thing; they differ only in a practical way. One is to have two paralleled strings of four speakers each (like the hi-fi annual's answer but without the cross-connections) . The other is shown here - four groups of paired, parallel speakers, connected in series.

The magazine's answer may have resulted from some editor seeing this diagram and deciding to save space by eliminating the vertical links.

What Is It?

There's nothing wrong with the set. I got the patterns (see next column, too) after a "friend" borrowed my bar-dot generator, and used a little screwdriver on the frequency-divider adjustments. While trying to fiddle it back into alignment without a scope, I hit these perfectly locked, but odd, patterns and photographed them.

They are caused by a very bad mis-adjustment on the frequency-divider (countdown) stages of the crystal-controlled bar-dot generator. The mis-triggering of the multivibrators apparently caused a complete cutoff of the mixer at some point in the cycle by clipping a pulse at the wrong place. That gives us the blacked-out parts of the signal, making the "vertical bar."

The stability of this whole pattern is due to the crystal oscillator, which controls all of the bar and dot frequencies, starting at 189 kc. Some of the lower frequencies are way off here, but the fundamental is still OK.

This is more proof of the fact that you cannot readjust one of these instruments "by hand." Read the instruction book and follow the correct setup procedure, using the scope and the correct coupling to get the right patterns.

 

 
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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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