1. Open up your machine. If you have chosen a Texas Instruments machine this might be your first stumbling point as the people at TI kindly chose to use star headed screws on a lot of their machines.
2. Repeatedly curse the name of Texas Instruments and add a socket set to the shopping list :)
3. While the machine is making a noise lick your finger tip and touch various parts of the circuit (do not try this on a high voltage circuit unless you want to die). If the pitch of the sound rises or drops or there is another interesting effect when you touch a certain solder point, narrow down exactly which solder joint it is by using a metal screwdriver and mark it or note it down. You've now found a body contact point or a potential pitch knob connection. (see common bends on page 3 for details).
4. Read the section on recognizing common bend points on page 3 and then get a piece of wire with both ends stripped.
5. While the machine is making a noise take your bit of wire and short circuit one solder point on the circuit to another point. At this point there are four options as to what might happen. If nothing happens then try another connection. If you get a massively loud distortion sound or a thumping hum then remove the connection quickly. If the machine crashes (see below) then start it up and try again. Best of all, if the machine produces a weird and unexpected sound then note down the connection and try it again. If the 'bend' you have found is reliable and repeatable then proceed to step 6.
6. When you have found a selection of decent connections you should solder switches or buttons across these points. You can also try soldering a potentiometer across the points to see if the effect is variable. At this point you might also want to consider where you are going to mount the controls on the casing.
7. And that's it for the absolute basics of circuitbending. We advise you now read page 3 of the bending tips and then rush out, buy yourself a Speak&Spell machine and get bending!
CRASHES & LOCK-UP'S:
DON'T PANIC, it's fairly inevitable that any machine you try to circuitbend will crash or lock up at some point during the bending process. You are attempting to do things to these machines that they were never designed to do. The most common symptoms of a crash are when the entire machine locks up and refuses to make any sound or operate in any way, although this state may also be accompanied by sad buzzing sounds or violent distortion noises.
If your machine crashes at any point you can usually start it up again simply by turning it off and back on again. You may find that you have to actually remove the power from the machine for a couple of seconds to get it working again. In these cases it is usually a good move to solder a 'push to break' button in line with the positive power connection. This means that when you press the button the power is disconnected and you should be able to restart the machine when you release the button. This is commonly called a Hard Reset button.
When bending programmable machines such as drum machines or some synths you may find that certain crashes will cause you to loose all the internal pattern memories. This is fairly common so be sure to back up any data you want to keep before attempting any circuitbending. It might also be a good idea to look up the factory reset procedure if your machine has one.
Sometime a crash is exactly what you wanted to happen so if the machine makes some bizarre noises as it gives up, try that connection again to see if it repeatable. Low number Casio SA keyboards are the kings of this bend (see voltage drop crashes on page 3)
In extreme circumstances when you can't get the machine started again you may need to discharge a capacitor or two. This is a last resort and if this doesn't work then you machine is probably dead. To do this simply remove the power from the machine and locate any capacitors on the circuitboard, especially ones near to the power input area. Discharge the capacitors by shorting one leg to the other with a piece of wire. This probably won't help but sometimes your machine will leap back to life. It is because of capacitors slowly discharging that you sometimes find that a machine you thought was dead leaps back to life after you leave it alone for a few days.