It may well be that ic 2008 is a component BU 2008 a four pin bridge rectifier rather than the typical in line integrated circuit.
As for 8403 - again that might be the component type rather than the circuit designation - PAM 8403 is a stereo audio amplifier and will have its number printed on it rather than on the circuit board - the circuit board will identify it with a different number.
Each of these may have a heat sink on top preventing you from seeing the component type number.
All of this is pure guesswork - no warranty expressed or implied.
Good Luck..., December 2016
