+/-15.7V does not sound right for the supply rails, unless you are talking about the low voltage supply. The power amp should be running on higher voltages than that.
Without a schematic there is not much anyone can suggest.
The schematic does not seem to be available online unless you buy it here:
http://www.majelectronic.co.uk/
Without a schematic there is not much anyone can suggest.
The schematic does not seem to be available online unless you buy it here:
http://www.majelectronic.co.uk/