I found a little keyboard attached to a book. I tore it off of the book, threw the book away and started in on the keyboard.
The construction of the keyboard was very simple. Not too many points for bends. That doesn’t stop me though.
The first thing I do on any project is find the timing resistor that manages the timing for the primary circuit. I found it with no problem at all and replaced it with a potentiometer and about 1M more resistance. I love the low end synth sounds more than the high end. That’s just me.
The next thing I did was to created a square wave generator to act as an LFO using half of a 556 chip. The output goes through two capacitors placed + to +. It gives the oscillator a better rise and fall off. A sort of envelope if you will.
I was playing around with this for a while. The problem I was having was that the keyboard runs off of 3 volts (two AA bats) and the square wave was running off of a 9v battery. I really wanted to have it all run off the same power source. I decided to try to hook up a 9v adapter input. That way I could just run it off of wall power and use the battery compartment for other things.
After much research and plauging questions on http://www.electro-tech-online.com/ I got most of the information I needed to feel confident that I could just hook it up without a problem.
The batteries were substituted with the wall adapter. Everything was working fine (there was definitely and audible difference. Most likely the cause was much more current.). I was trying to create a voltage divider to give me the 3V I needed to power the keyboard.
I couldn’t seem to get a good balance between the resistors heating up (around 100 ohms) and not enough current to power the keyboard (anything over about 400 ohms). In the proscess of experimenting with the different values I fried both the keybaord circuit and the 556 ic.
This really pissed me off. Now, I’m out of 556’s (until I get my order in) and I just fried 15-20 hours of fiddling around. Thankfully I had made my usual run of the thrift shops and found another keyboard that was almost identical. Not as pretty though. Not that that matters because I was going to paint it anyway.
Another one bites the dust. I did however get a lot of useful information (for the most part) about wall adapters and using them instead of batteries.
You can read the conversations here.