Full drop in TI99/4a Power supply replacement. No soldering.
This board is a drop in replacement for the internal TI99/4a power board that uses the pin headers to connect to the motherboard. There is a header to install the pigtail that some early units used.
It uses a regulated +12V DC external power supply, 48 watt or greater. (4amp)
Use a good quality supply, as this is the actual +12v for the computer.
This uses a DFR0831 5v buck converter, that's rated for +5v@4a, but I recommned no more than 3.5a draw.
There's a error on the schematics, the 220ohm resistor isn't enough for modern leds, so I recommend a 560ohm for bright or 2.2k for dull.
You should also use a 2.5mm thermal pad underneath the DFR8031 to help cool it.
-5v is provided with a P78E05-1000 switching regulator...This is rated for 1amp compared to the originals .5 amp. -5v is basically there for the 4116 ram.
The SUP53P06-20-E3 mosfet is there for reverse voltage input, but you can leave it out by connecting pins d & s ( the two close to the edge of the board)
This is a remix of the TI99-4A-dc-power-board by jonn-reenthused
https://github.com/jonn-reenthused/TI99-4A-dc-power-board
I wanted more than a 2a 5v supply, so I spun this up.
This project was made using EasyEDA, because the original version I forked this from was. I'll eventually move it to kicad.