Hi All
Many thanks for all the replies. I have de soldered the regulators and they are not the source of the problem. On a positive note this is the first time I have managed to remove anything with more than 2 connections without destroying the board, so a new skill using hot air has been acquired...... Removal and replacement of the amp is just beyond what I can muster, so I guess I am the proud owner of an undersized boat anchor/small project case.
As it's xmas time I guess a further spend is in order.........choice between another similar or upgrade to a decent headphone amp/dac and separate power amp.
Hope you all have a good new year