From having a quick look at the datasheet for the MC34063A, it looks like that's doing all the regulation for the 15V supply rails, if it goes up in smoke again, you can buy an LM7815 (+15V 3-Terminal Regulator), and an LM7915 (-15V 3-Terminal Regulator) and use them to build a replacement +/- 15V power supply for the PV6 mixer, if you want I can draw up a circuit diagram for the replacement power supply and post it here.