It steps down the 12V from the lighter socket to 9V which is used by the CD player. Different CD players may require different voltages, so just use the correct regulator. All the 78xx series regulators have the same pin out, so the circuit is universal.
Part Total Qty. Description Substitutions
C1 1 1000uF 25V Electrolytic Capacitor
C2 1 10uF 25V Electrolytic Capacitor
C3 1 1uF 15V Elextrolytic Capacitor
C4 1 0.1uF 15V Electrolytic Capacitor
U1 1 7809 Or Other Regulator (See “Notes”) See Notes
MISC 1 Cigarette Lighter Plug, Plug For CD Player (See “Notes”), Heat Sink For U1, Wire, Case.
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