The CT-64 was one in a line of video-display terminal kits produced by Southwest Technical Products in the mid-to-late 1970s, directed towards the then-new hobbyist/personal computer market. The CT-64 was a lower-cost alternative to commercial video terminals.

• Schematic (PDF)
• Unit Log

The CT-64 With a somewhat oversized monitor, and a screenshot showing the character set and display size of 16 rows by 64 columns.

The sync generation circuitry does not use a crystal, instead a phase-locked-loop is constructed from a 555 and some discrete JFETs, to lock the sync to the mains frequency and multiply it to get the horizontal sync. The discrete elements of the PLL can be a little finicky but if operating properly a quite stable display is produced.

Front and rear views. This front panel has some additional holes drilled for switches for the screen-read board. The rear panel has also been adapted for a BNC connector for the video and an IEC power connector.

Internal views. The memory, screen-read and communications boards have been removed in the right photo. The aluminum angle braces going across the keyboard are not original, they were added to improve the rigidity of the keyboard.

Keyboard removed for view of the complete main board.

The plug-in boards: memory board with 2 rows of 21L02 1024*1 RAM chips for two pages of memory, the serial communications board, and the optional screen-read board.