hi peeps , just bought a 2000 v plate gti 1.8t off a friend , the car has been sat for 6 months with no battery in it . got it running and have driven it home , bar the rusty brake discs all seems well except the stereo .. it wont turn on at all , i press the power knob and nothing happens . i have the code card with a 4 digit code 0718 which ive tried entering , but nothing .. infact the numbers on the stereo only go from 1-6 ... (im assuming the buttons to the left and right count for numbers too) any ideas

its a gamma stereo tape deck with a changer in the boot