For all modifications, check the
high resolution image of the modified board
1) The d-sub connector is soldered to the ground plane of the PCB. Cut the metal that goes from the ground points to the screws that hold the d-sub connector.
2) Remove the 10 microfarad capacitors C25, C61, C45, C47, C51, C53, C59, C65, C73, C81, C57, C63, C71 and C79.
3) Remove the surface mount resistors R15 and R16.
4) Put the plus side of four 470 microfarad, 6V capacitors into the minus holes of C59, C65, C73 and C81. Bend the wires for the capacitors to lie on top of the ICs. Put a 2.2 k resistor to ground from each of the negative terminals of the new capacitors. Be careful to not place any of these resistors to close to C51 where 470 microfarads will be mounted. Put a 6.8 k resistor from each of the not grounded ends of the new 2.2 k resistors to the positive terminal of the corresponding input capacitor C57, C63, C71 and C79.
5) Mount 15 ohm resistors from C38 to R15 and R16. For C38, use the entire copper area of the via hole, C38 and pin 14 of U7. For R15 and R16, use the side connected to pin 23 of the AK4524.
6) Mount a 1N4001 diode from C38 to the output pin of U5 with the cathode towards U5. For C38 use the same area as for the new 15 ohm resistors.
7) Mount 470 microfarad 6V capacitors in the locations C25, C61, C45, C47, C51, C53 and C37.