| Home | “If your boom box already has auxiliary inputs, then the procedure that we are describing is completely unnecessary, but, unfortunately, boomboxes with this feature are rare.” |
How-to Tip: Turn Your Broken Boom Box into a Set of Amplified Speakers
By Howard Charles Best, November 9, 2001
(LLBest.com)
Two things which tend to go bad relatively quickly are cassette boomboxes and inexpensive stereo headphones. The most common difficulty with cassette boomboxes is that the cassette player starts to “eat” cassettes. The most common problem with stereo headphones is that one channel becomes intermittent or completely stops working.
Quite often these two defective pieces of equipment can be combined to produce something very useful: amplified stereo speakers. Such speakers can then be used with a computer or a “Walkman” type cassette player, CD player or MP3 player. In addition, they may be used as remote speakers in a multiple room sound distribution system.
If your boom box already has auxiliary inputs, then the procedure that we are describing is completely unnecessary, but, unfortunately, boomboxes with this feature are rare.
1. Cut the cord of the stereo headphones so as to make the cord as long as possible. Strip the ends, and use a continuity tester or ohm meter to make sure that both the right (red wire) and the left (white or black wire) channels are good. If one of them is not good, cut the cord a little shorter, and strip and test again. Repeat until both wires are good.
2. After taking the back off of the boombox’s case, drill a small hole through it near the boombox’s volume controls, and run the headphone cable through the hole. Tie a knot in the cable on the inside for strain relief, allowing enough “slack” for the wire to reach to the volume controls after the back is put back on, and the knot in the cable is pulled snug against the hole.
The next 3 steps refer to the following schematic diagram which represents a portion of the boombox’s circuitry:
The left and right channel circuits are identical.
3. Identify the three connections (#1, #2 and #3) of the boombox’s left and right channel volume controls. The easiest way to do this is to use an ohm meter. First connect the ohm meter’s black lead to ground. The connection which remains at zero resistance as the volume control is changed is connection #1. The connection which varies in resistance as the volume control is changed is #2. The one which remains at the same resistance as the volume control is changed is #3. As an additional check, measure the resistance between #2 and #3, which should also change when the volume control is changed. When the resistance between #2 and #3 is at it’s maximum, then the resistance between #2 and ground should be zero. When the resistance between #2 and #3 is zero, then the resistance between #2 and ground should be at it’s maximum.
4. Cut the boombox’s two conductors which go to the two connection #3s (right and left channels). These are usually printed circuit board traces. The best way to cut through them is to (very carefully) use a sharp Exacto knife or utility knife.
5. Solder the ground wires of the headphone cable to connection #1. Solder the left channel wire to the left channel volume control’s connection #3 and the right channel wire to the right channel volume control’s connection #3.
6. Before putting the boombox’s case back together, it’s a good idea to test your handiwork. With the boombox’s volume control turned down, plug it into the AC, turn it on by switching it to “radio,” and then plug the newly installed miniphone plug into something which is putting out a continuous signal such as a portable radio. Slowly turn up the volume and make sure that both channels are working.
7. If both channels are working, then make sure that they are not reversed. In order to test this, unplug the miniplug and turn the volume of the boombox up all the way. Touch the tip of the miniplug, and a hum should come out of the left channel. If the hum comes out of the right channel, then the channels are reversed, and the two wires connected to the two #3 connectors should be reversed in order to correct the problem.
Questions, comments and suggestions are welcome.
Howard Charles Best ()
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