Didn't find your amplifier listed in Sam's Photofact index. Might try Paul's UK forum?
http://www.vintage-radio.net/forum/index.php
Norm
:I have a philips AH 5781 amplifier. I have been looking for any source of information, schematics, books or any information on how to find parts and schematics for this model. Any information will be very much appreciated. My thanks in advance.