Ian Johnston purchased a used Pioneer amplifier that was slightly defective. The amplifier would not function when the tone controls are switched in (this amp has a bypass switch which allows these controls to be bypassed). Turns out that the amplifier was fine, the issue was missing RCA Jumper Links , you can see what these jumpers normally look like in the picture below.
This amplifier doesn’t have a remote control so the next task Ian tackled was to install a motorized volume potentiometer which is controlled from an Arduino Nano microcontroller. An IR receiver will be interfaced to the Arduino so that the system can be controlled by a standard remote control. There was no 5 volt power rail on this amplifier and the lowest usable voltage that could be tapped off was 44 volts so a normal LM7805 could not be used, a LM2575HV-5 (PDF) was used instead since it can handle the higher input voltage. The result is great other than a piezo buzzer that beeps each time the volume is pressed, Ian notes that this has been reduced in volume but I am thinking a flashing LED might be a better indication. You can see the full build details including the Arduino code here.