To locate the clock resistor:
- Remove the circuit from the housing of toy
- Continuously make sound with the toy.
- During audio playback, run fingers over the components and listen to any variations in playback rate.
- Narrow down this change to one component (or the connection between two point on the board).
Once the clock resistor has been found, a number of different modifications can be made:
- A physical pot can be added to the circuit at the two points where a change of pitch was detected. The physical pot will only change the playback rate up (and not down).
- The clock resistor can be removed by desoldering carefully. The clock resistor can then be replaced with a physical pot - the middle leg and one outside legs are connected to the two points where a change of pitch was detected.
- Instead of using a physical pot, a light dependent resistor can be used.
- Instead of using a physical pot, a flex sensor can be used.
- Instead of using a physical pot, a digital potentiometer can be used.
- Instead of using a physical pot, a series of pots wired as a sequencer can be used.
In the example shown below:
- The circuit board of the toy is removed from the housing
- The clock resistor is located
- The clock resistor is removed via desoldering
- Two new connections are soldered on in place of the clock resistor. This is achieved by added some solder to each point on the circuit board, and the inserting a small wire per connection.
- Note how much of a playback rate change can take place when the clock resistor has been removed
- A light dependent resistor is added, and now controls the playback rate