Back in the late 1980's, I was in a vocational electronics program at my high school and I was also an avid electronics hobbyist. One of the first projects I built was an audio frequency generator from plans published in the now defunct Radio-Electronics magazine.
Hello, this is the 1980's, we want our Audio Frequency Generator back!
The audio frequency generator was a simple circuit that consisted of a single LM386 integrated circuit. It's output was a triangle wave from 0 to 25Khz. A three position switch was used to put the circuit in standby (no output), low, or high frequency output. It also had a volume control to control the amplitude. The power switch was integrated into the volume control. This circuit used a small incandescent light bulb pointed at a cadmium sulfide light sensor as feedback for frequency stabilization. As you can see, my craftsmanship on this first project leaves much to be desired. I didn't even bother to install a knob for the variable frequency control!
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The inside of my Audio Frequency Generator Project
I made the printed circuit board myself using a printed circuit board making kit I purchased from Olson's electronics. We had a local Radio Shack but I found that our local Olson's store was a little cheaper to purchase discrete parts and the printed circuit board making kit. As you can see, I had to modify the printed circuit board dimensions to fit in the project case. The project case was recycled from a high voltage tester I built in vocation electronics class. I fried the components of the high voltage tester by setting the front switch to the wrong voltage range. Most of the components (resistors, capacitors, potentiometers) were recycled from other electronic projects or salvaged televisions and radios I trash picked. Even the 9 Volt battery clip was recycled. I tore apart a dead 9 Volt battery and salvaged the terminals. Looks like something from MacGyver would build! Time for a Ty Pennington style "Extreme Makeover" of my Audio Frequency Generator project!
Step 1 Disassemble my Audio Frequency Generator Project
Remove audio output connection points from the front panel. See areas circled in red.
Here is the back side of the printed circuit board I made using the Olsen's Printed Circuit Board kit.
All of the electronics components removed from the old project case.
Here is a picture of the "sad" old project case.
Picture of my home made 9 Volt battery clip.
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Step 2 Replace Resistors
The original resistors were salvaged from an old AM radio. They took a beating during the "recycle" process so I decided to replace them.
Picture of the old removed resistors.
Picture of the printed circuit board with brand new resistors installed.
Step 3 Replace Capacitors
Many of the original capacitors were salvaged from a TV and had high voltage ratings which is why they are physically large.
I replaced the capacitors with low voltage ones that have a working voltage or only 15 Volts. This is why they are much smaller.
Step 4 Install Integrated Circuit Socket
To aid in troubleshooting and replacement, I unsoldered the LM386 Integrated Circuit and installed a DIP (Dual Inline Pin) socket in its place (see area circled in red). I then re-installed the LM386 Integrated Circuit in the DIP socket.
Step 5 Prepare the New Project Case
I used a wooden craft box purchased from Amazon as a project case. I simply removed all hinges, clasps, and other hardware.
I turned the craft box base upside down to use as a chassis. I use the top or the craft box as the front panel. I did a "dry" of of all parts then I treated the craft box to two coats of water-based Polyurethane lightly sanding between coats.
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I used a Darice wooden craft box for my Audio Frequency Generator Makeover project.
Step 6 Final Assembly and Testing
A much neater wiring of the printed circuit board. Notice I installed a "real" 9 Volt battery clip!
Back view of my updated Audio Generator Project.
Front view of my updated Audio Generator Project.
Picture of all of the parts I replaced in the Audio Generator Project.
With tips from this blog, you too can breath new life in an old project and give it a Ty Pennington style "Extreme Makeover".
Who Writes This Blog?
John is an IT professional from Cleveland, OH who enjoys amateur radio, ham radio, metal detecting,
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