December 1961 Radio-Electronics
[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.
In May of 1961, Radio-Electronics
magazine began running a monthly quiz type feature called "What's Your EQ?" "EQ"
stands for Electronics Quotient (a play on "IQ," obviously). For the first year
or so, solutions were provided in the next month's issue, but, probably at the request
of readers, solutions were printed in the same month's issue. The EQ challenges
were provided by readers who were paid $10 when published. $10 in 1961 was the equivalent
of about $93* in 2021 money per the
BLS Inflation Calculator, so it wasn't chump change. "Black Box" problems
were very popular, and arriving at a workable solution (sometimes there was more
than one) often took some creative thinking. The box might contain relays, vacuum
tubes, semiconductors, resistors, capacitors, inductors, transformers, incandescent
or neon bulbs, motors, or just about any other kind of component. My approach is
to say there is an elf inside who has an ample supply of items to manipulate the
output(s) as required based on the input(s). Of course he also needs a copy of that
month's Radio-Electronics in order to know what to do ;-)
* At the current rate of inflation, the purchasing power will be far less before
What's Your EQ?
It'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.
What's The Sync Trouble?
The Emerson TV had no sync. Using
his scope, the technician found no sync on the plate of 5U8 (see schematic). Video
to the grid was normal. Using a vtvm, he found a negative 12 volts on the grid,
due to grid rectification, when the set was tuned to a station. Off-station the
grid voltage dropped to -3. Next he measured the plate voltage and found it to be
60 - on station or off! The tube was good and the socket was OK.
You have the facts - what's the trouble? - Wayne Lemons
The life of the high-intensity lamp shown
below is reduced to 30 seconds if external air cooling is not provided. It is therefore
necessary to assure that the blower is always the first to be turned on and the
last to be turned off.
2 stdp switches
1 blower with step-down transformer
1 high-intensity lamp with step-down transformer
1 117-vac power cord
Wire the five basic components so that no matter which of the two switches is
activated first, the blower will be turned on first and also, no matter which of
the two switches is deactivated first, the blower will be the last to be turned
off. - Max J. Fuchs
The Infinite Black Box
With the Black Box and external resistors
shown in the drawing, an ohmmeter connected between terminals A and B reads infinite
resistance. What active circuit is in the box? - Richard L. Koelker
What's Your EQ Solutions (from the
January 1962 issue)
What's the Sync
The technician first thought that the trouble must be due to an open cathode
but, since there was obviously grid rectification and the cathode would have to
be in circuit to produce it, he discarded this idea.
The trouble was finally found to be an open 2.2-meg grid resistor. This made
the tube block since there was no grid return. Measuring with the vtvm provided
an 11-megohm resistance to ground and the tube operated almost normally, but of
course it blocked again when the vtvm was moved to measure the plate voltage!
The circuit below is so arranged that no
matter which switch is thrown first, the blower will be turned on first and off
last, thus assuring air cooling at any time the lamp is burning.
Infinite Black Box
Terminals 1 and 3 are the input to a DC amplifier with a voltage gain of 1 and no phase inversion. The output of the amplifier
is between terminals 2 and 3. Thus for any input between terminals 1 and 3, the
same voltage will appear at terminal 2. Both ends of R1 are then at the same voltage,
no current can flow in the resistor and the input resistance is infinite. This is
a good example of feedback increasing the input impedance of a voltage amplifier.
Posted December 6, 2021