DESCRIPTION:
This modification can be performed on the NEC Turbografx TurboDuo or Turbo
Express hand-held system. I must caution you that this is "not" a task for the
novice and I shall not be responsible for any damage(s) that may occur to your
system. The most difficult part of this project is to fit so many added
components and wire connections inside such a small unit like the Turbo
Express. I will leave that challenge to you. The only difference between the
Turbo Duo (US) and PC-Engine (JAP) HU-Card is the fact that the 8 Data Bit
signals (D0,D1,D2,D3,D4,D5,D6 & D7) are reversed. So depending on the
chosen Mode, we must direct these eight signals coming from the HU-Card in the
appropriate order (D0-D7 or D7-D0) to the system data bus. The above schematic
will allow you to do just that. Carefully study the two figures below of the HU
connector pinout. Use a small and sharp hand wire cutter to cut out the blue
sections of the eight data lines-the purpose is to isolate these signals from
the HU-Card and the system. Follow the schematic above to make all wire
connections. Verify your work and cross your fingers. Good Luck.
PARTS NEEDED:
- (4) 74HC4066 ICs - DIP or SMT
- (1) Solder and 30-gauge wires
- (2) 1/4W 10K resistors
- (1) Miniature Slide Switch
- (1) Phillips screwdriver
- (1) Soldering iron with a small tip
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