Introduction: Hack Digital Radio, Replace the Volume Control

Few moths ago, my mother come back from Italy and brought me a digital radio in the form of an car (Porsche Cayenne ?)

it is cool, no ?

But an issue is present, on every boot, the volume is set to 84% ... It's very loud !!

I don't understand why each FM frequence are saved into the memory but is not the case for the volume level ?

It is why i decide to try to control the volume from an external potentiometer

Step 1: Identifying the Amplifier Chip

After i have identified the amplifier chip : an MC4863 (Dual 2.2W Audio Amplifier) i downloaded the datasheet to understan how the gain is controled

I found the following text and image in the datasheet:

The first amplifier’s gain is externally configurable, while the second amplifier is internally fixed in a unity-gain

The datasheet talk about a resistor of 20Khom to control the external gain but on the PCB i found two resistors of 67Khom ... may be to have a satured gain ?

Step 2: Build a Dual Potentiometer From Two Traditional Potentiometer

The Chip MC4863 is a dual Audio Amplifier so that means it has two independent output signals ... which mean it require two different potentiometer in one package

I don't have one, so i build it one ...

Step 3: Fix the Dual Potentiometer

After the dual potentiometer is done, i fixed into the car

Step 4: Replace the 67Khom Resistors by the DIY Dual Potentiometer

I disoldered SMD resistor and connect my DIY dual potentiometer

Step 5: The Final Result in the Video