Back in 1985, I was born.
But that’s beside the point; that same year, the Roland Corporation also manufactured my TR-707 Drum Machine! I received it as a birthday present in 2004 (or thereabouts), and after playing with it a few months, me being the hacker that I like to think of myself as, I proceeded to modify it in many different ways. Among them, I wired a TON of toggle switches to the panel, forming a matrix of connections between various sound effect data lines.
These are fairly well-documented circuit bends, and most of the connections create some very unique sounds and effects that I can instantly recognize when I hear in a track (I say that like it happens a lot, but it doesn’t and all I can really think of right now is Last Step (aka Venetian Snares) – “Last Step”). I used it to make some videos recently (before the mod I made this post to discuss was performed):
I have yet to find any articles on the backlighting of a TR-707 or similar device (or perhaps this is just me being too lazy to figure out just what similar machines might exist and searching for “
So I knew what I needed finally, which was another polarizing film like that found on the outside of the LCD. Long story short: I had an old broken TI-89 graphing calculator which is conveniently based on the same technology, and the film is just slightly smaller than the TR-707 LCD; in fact, it is the same size as the silk-screened grid on the thing, which is all that needs to be backlit anyway! Excellent!
Now for the important, non-ranting bits of information! My backlight consists of a 1/8″ thick piece of mirrored acrylic cut to fit behind the LCD.
I then took some white LEDs, and ground them down to fit flush against the edge of the acrylic; in total, two sets of three, powered by the -10V regulated supply I had to make with an LM317 because I burned out the transformer on board many years ago (that’s another story to tell altogether, but suffice to say that I didn’t know what was messed up for 3 years and only fixed it last year at some point, finally).
I also went ahead and put another transformer in from a wall-wart so that the whole thing can be powered from a normal computer-style power cord. There’s also a small fan to keep the whole thing cool.
The other edges of the acrylic are covered with foil tape to keep light inside, the surface was roughed up a bit to improve diffusion of the light, and the TI-89 polarizer is stuck there. The whole thing is then stuck behind the LCD and everything put back together. Fairly simple idea, but I’m the only one I know of who has documented this process. To do it to other machines, it may not require more broken TI-89s, because the polarizing film can be purchased online in a few places, such as this one.
It is wired with the backlight on all the time because the LCD is readable in both normal conditions and the dark so I didn’t care about setting up a separate switch for it. I find it works nicely, despite some swirls of distortion in various parts (due to the polarizing film not being meant to be removed and placed elsewhere). Finally, I used GIMP to mock up some new labels for the panel (that was a lot of fun, I swear), and printed out on white adhesive label sheets.