How to add RGB on TI99/4A?
A working TI99/4A Computer
TMS-RGB Mod Board (Assembled)
8 Pin Mini Din Female connector
8 Pin Mini Din Connector Board from OSHPark (Optional)
8 Pin Mini Din Scart RGB Cable
3x 560 Ohm Resistors
1x TMS9928A Chip
A Phillips Head Screwdriver
A decent Soldering Iron
Some Soldering Wires
Desoldering Braid, Pump, or Hakko Desoldering Gun (If you want to do no-cut method)
An OSSC, a Framemeister, a PVM RGB Monitor, or any Scart adapter (Required for RGB)
Step 1: Unscrew all of the screws from the bottom of the TI99/4A and then carefully open it.
Step 2: Unplug the power supply from the motherboard and unscrew all of the screws from the motherboard. And don't forget to take off the cartridge connector and take out the RF Shield, as well as the keyboard connector!
Step 3: After you open the RF shield from the motherboard, you will see the TMS9918A Chip, so you need to remove it. If it is socketed, it is very easy to remove it. Then, replace it with the TMS9928A Chip.
Step 4: You need to solder the TMS RGB Board onto the bottom of the VDP Chip like this:
And solder the wires to the chip:
And don't forget to feed the wire for the audio which is Pin 3 of the TI's Video connector.
Step 5: Solder the three 560 Ohm resistors to those places like those:
Step 6: If you want to do no-cut method, simply desolder the original video connector off from the board and feed all of the wires to the 8 pin mini din connector.
Step 7: Test is to make sure it works before putting the TI back together. (If it works, then move on. But, if it doesn't work, check your work and try again.) Make sure you mount the RGB connector!
Step 8: Carefully put the console back together, and then enjoy!