Hi all, have tried changing out the 5150 chip and still no joy (tried 2 of them) - any other ides would be greatly appreciated, thankyou.

The socket itself might be bad.  You can test it with your DMM on continuity/resistance setting.

Follow the traces from each socket pad to a nearby pad on the baord and see if they have continuity.

Edit - Any chance you could post a picture of the socket with no chip inserted ?