These instructions apply to the Vox V847 (US reissue) and Rev.D Dunlop Crybaby pedals. The circuit boards and wiring are very similar, the only difference being the Dunlop has a DC jack.
Rev.D Crybaby diagram
1. Desolder the wiring from the existing switch.
2. Remove the switch and replace with the new one.
3. Solder a new length of wire to the upper right lug on the switch.
4. Cut the brown wire where it enters the white connector.
5. Solder the free ends of the brown wire and the new wire to the lower left lug on the switch.
6. Solder the white wire to the lower middle lug on the switch.
7. Solder the short blue wire to the lower right lug on the switch.
8. Solder the green wire to the upper middle lug on the switch.
9. Solder a new wire between the upper left lug on the switch and the grounded lug of the pot.