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Don't feel too bad if you bomb out on any of these three "What's Your EQ?" challenges. The first one with the tornado waveform on the oscilloscope is something only a person very familiar with television circuit troubleshooting would be able to figure out. In 1961 when it appeared in Radio-Electronics magazine, the readership included many such savvy guys, but not so much now, especially since almost nobody deals with CRT deflection circuits. With the "Simple Impedance Problem," the first thing I did was re-draw the circuit to reflect the four parallel branches in an easier-to-conceptualize format. I admit to not observing the component value relationship pointed out in the answer. I'm a bit dubious of the creator's claim regarding what makes it simple to analyze. If I had the time, I'd plug the circuit into a simulator and see if he's right (which he probably is right). Any comments? The only one I wasn't sure about was number 2. Maybe you'll do better.

The EQ's are now the most popular department in the magazine. Our mail is reaching an all-time high! We just can't answer individual letters, but will continue to print the more interesting solutions (the ones the original authors never thought of!).

Here are a few more we hope our readers will find challenging. And if you can develop an original EQ that will stump our readers, send it to us. We pay \$10 and up for each one accepted. Write to EQ editor, Radio-Electronics 154 West 14th St., New York 11, N.Y.

An Electronic Ground?

This Zenith chassis 15Z31 came into the shop with what appeared to be a folded-over ground symbol. The shop technician took one look and pointed out the trouble, not by deduction, but because he had had the same trouble before. Could you have done as well?

- Wayne Lemons

Simple Impedance Problem

At 1,000 cycles, what is the impedance of this circuit (to the nearest ohm) between points A and B, and what is its phase angle (to the nearest degree)?

- Charles Erwin Cohn

Electronic Photogram Puzzle

This novel, puzzle can provide many minutes of fun for the electronic technician and hobbyist. The object is to see hew many of the radio-electronic components you can identify correctly in the photo-diagram. Watch out - a couple foreign (nonelectronic) parts are thrown in just to mislead you!

- John A. Comstock

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.

## Solutions

Electronic Photogram

1. Nailclipper (a foreign part!)

2. Fuse holder

3. Drill chuck key (a foreign part! )

4. Rubber grommet

5. Trimmer capacitor

7. Control (potentiometer)

8. Dual-clip (Mueller No. 22)

Simple Impedance Problem

The gimmick here is that the resistors on the inner ends of the four arms radiating from the center are each 1/17 of the resistances on the outer ends of the corresponding arms. Hence the various inductors and capacitors are connected between points of equal potential, and have no effect. Therefore the phase angle is exactly zero, and the impedance is merely the resistances of the four arms taken in parallel, which comes to 231 ohms.

An Electronic Ground?

The shop technician didn't agree with the home technician that the trouble was "probably the yoke." Instead he pointed to the three-section electrolytic shown in the photo. "This electrolytic has developed an open common connection internally," he said, "I'll bet money on it. When that happens all the waveforms of the power supply and the horizontal and vertical sweep systems get all mixed up together and what you see on the screen is the result of it. Since the entire can is defective, you can't find the trouble by just bypassing one section with another capacitor, although you will probably note a little improvement or at least change if you shunt-test any section.

Posted July 30, 2024