Some PIcmicro MCUs require a "reduced" High Voltage during programming. This PDF provides step by step instructions with photos to modify QuickWriter for Dual-VPP operation.

All Hardware versions from 1.0 to 2.1 can be user-modified to support Dual-VPP operation. Versions 3-0 to 3-E already support Dual VPP when used with software 2.6.7 or above.