Modern Replacement Power Supply for a TI-99/4A

Description

The computer was pretty mint. But did it work? I had no way to tell, because the external power brick was missing from the lot.

Some investigations later, I ran across some work by a fellow named Jonn Blanchard, hosted on OSHW. The link I had is here:
https://oshwlab.com/jonn.blanchard/ti99-4a-replacement-power-oard_copy_copy_copy_copy
but it seems to be deleted now.

Using his basic concept, a series of buck converters on a protoboard with an external power brick to get the necessary voltages, I ran a test, and sure enough the machine would boot.

Though I kept my eyes open for an orphaned power brick, I had to assume I would never find one. So, the rest of the story is about creating a drop-in replacement for the internal TI power supply board.

Files

Artwork.png Portable Network Graphics (PNG) - 107.27 kB - 09/20/2026 at 20:53		Preview

pcb final 4.svg svg+xml - 46.77 kB - 09/20/2026 at 20:52		Preview

pcb edit 3.svg svg+xml - 100.37 kB - 09/20/2026 at 20:52		Preview

pcb edit 1.svg svg+xml - 79.68 kB - 09/20/2026 at 20:51		Preview

v78xx-1000.pdf 7812-1000 Datasheet Adobe Portable Document Format - 1.68 MB - 09/20/2026 at 20:50		Preview

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Modern Replacement Power Supply for a TI-99/4A

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Just one more thing

Description

Files

Artwork.png

pcb final 4.svg

pcb edit 3.svg

pcb edit 1.svg

v78xx-1000.pdf

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