Pins Bu, BH and BL select the band you are listening on. The plus side is these things use I2C, which is a standard. Notice how the volume and input jacks were recycled. In the end I was able to pick up all of the local FM stations, along with several unidentified signals in the other bands. However interface is much more difficult, because you need to communicate with PLL and synthesizer chips to set the receiving frequency.
The final demodulated signal exits the chip at pin 11 and is sent through some audio filters before being amplified. The discriminator on pin 10 is used to extract the audio signal. This eliminated noise problems altogether, and the tuner is now run from a mains powered supply.Digital TV tuner RadioI found a digital tv tuner of the type UV1316, which is I2C compatible. It requires a +33 and +5 volt supply, but is otherwise quite easy to use. Every analog tuner will have equivalent pins so it’s just to find out which are which. The android app and microcontroller firmware can be downloaded here. The TDA2822 is just wired up like they show in the datasheet with an AF filter on the input.
The intermediate frequency output can be plugged into the circuit above. To control the tuner, I constructed a simple circuit consisting of a microcontroller which received control signals over bluetooth. The stepper motors are easy to extract from the drives, and are ideal for many applications. Most tuners use 0-30V however, so keep this in mind. The circuit would then decode the bluetooth data, and write data to the appropriate registers in the tuner via the I2C interface. An Android app was written which would translate the desired listening frequency into the correct register values, which are then sent to a connected bluetooth unit. Now obsolete, such disk drives are often available on the surplus market for a small fraction of the motor’s original cost.