Booming

I have a problem with collecting things. Some might call it hoarding, I call it electronic adoption. One of the items I am constantly on the lookout for is a boombox. You know, those huge clunky 8+ D-cell battery monsters from the 80s. Awkward to lug around, audibly intrusive into other's bubbles, and built around a physical form of media that is all but extinct in the present day. I find it interesting that the image of a boombox is still an icon in today's graphics, and recognizable to those kids who have never even used a cassette tape. Kind of like the floppy disk icon still being used as the universal "Save". But anyway, on to the point of this post.

Some of these boomboxes were built with TVs inside of them. The model I find most often like this is the Emerson XLC-450.

In actual boombox levels, it's a pretty weak contender. One thing going for it is a line-in option, but this guy pretty much just sat on my shelf gathering dust until I started to read up on possible ways to utilize the TV screen for some cool visual stuff. There are plenty of tutorials around the net on how to turn an old TV into somewhat of an oscilloscope, so I figured why the hell not. This will be the third of these models that I've modded this way, so I decided to document the process.

DISCLAIMER: I am not any sort of electronics expert, and honestly am surprised that I didn't blow something/someone up in this process. Attempt at your own risk.

So a CRT display basically works with two coils. One coil moves the electron beam horizontally, the other coil moves it vertically. Looking inside this boombox we can see these coils, with four wires leading up to them.

Two of these wires control the horizontal coil, two control the vertical. By trial and error you can find the pair that controls the vertical coil (disconnecting the vertical coil will result in a horizontal line on the screen, and vice-versa).

What we're after are the pair of wires that control the vertical coil, which are then resoldered onto the horizontal coil. This is because of the vertical frequency 60Hz, as opposed to the horizontal of 31500Hz, gives us the output that we're after. Switching the wires around the other way (horizontal coil wires stay put, input on the vertical coil) gives a horizontal line that just moves up and down with the input signal. At this point we're ready for some input! I simply split the right channel into the vertical coil. Feeding in a square wave gave me this as output:

Not very impressive so far. If you look around the board itself, you'll see several potentiometers that control the various properties of the screen. (SERIOUSLY: Be careful about poking around in there). 

I'm sure these vary from TV to TV, but by twiddling around with different positions of the pots I eventually got a nice solid horizontal line across the screen. The only thing left to do: dim the lights and play some tunes!