Kenwood ud-100 Hi-Fi System Faulty 8-922 Pre Amplifier?

Hi,
I have a Kenwood ud-100 Hi-Fi System. When the 8-922 Pre Amplifier is plugged in and the System is turned on, does for a second then turns off again. When the pre-amp is disconnected, the system will turn on ok.
Does anyone know what components maybe causing this fault? The only thing I can see is that little transformer gets very hot.
Thank you.