hifi engine

pioneer sx 690

Could anyone explain why I AM GETTING AROUND 7 TO 12 VOLT DC AT THE AUX AND TAPE RECORD SOCKET WHEN THE INPUT I S SELECTED .THE FAULT IS ALSO PRESENT ON THE OTHER SOCKETS WHEN OTHER INPUT ARE FUNCTION ARE SELECTED.I HAVE CHANGE THE STK BUT SITL 7 TO 12 VOLT DC ARE ON BOT ITS INPUT AND OUPUT PINS EVEN WHEN BOTH ARE ISOLATED FROM THE CIRCUIT.