Several years ago, I picked up this device to transmit audio from various devices to my stereo equipment via an FM signal. While this worked well enough, interference aside, one thing that always annoyed me with this device was the rather bulky limitation of its auto style cigarette lighter power adapter.
Initially I bought a compact AC to auto auxiliary power adapter. Although this worked and I was able to use the device fairly well, it lacked a certain finesse. So this past weekend, in less than an hour, I decided to hack the device and remove the bulky auto auxiliary power connection.
This was relatively simple to do, but I cracked it open first to ensure that I wasn’t trekking down a fruitless path. A hammer and a paint chisel later, I removed the power connector’s lid and was able to examine the internal circuitry. I found a yellow wire connected to the positive 5 volt source and an unlabeled black wire which logic dictates would be the negative 5 volt connection. This is fortunate because USB connections are based on 5VDC, so this cut my crafting time and parts list in half. In my book, the less soldering the better. Not that I mind soldering at all since I happen to be quite good at it, however; it’s just strenuous and somewhat time consuming.
Then I cut a USB extension cable and used the knowledge of USB pin out wiring pin 1 is the +5vdc and pin 4 is the -5vdc. The only trick was determining which of the four wires inside the extension cable went to the appropriate pins. Using my handy multimeter and a modified test lead, I was able to determine that the red wire was the +5 and the black wire was the -5.
Armed with my wire mappings from both components, I soldered the red and yellow wires together, as well as the two black ones to each other. Then I covered them in some nice black heat shrink tubing. Now I have a compact device that p0wers off of the 5VDC USB port on my laptop.
However, don’t think I wasted the auto power adapter. As an added bonus, I ended up connecting the female end of the USB extension cable to the cigarette lighter adapter so I can still use this device like it was originally intended. I’d say all in all, it’s not bad for a spare hour on a Sunday afternoon.