Lot #285
Lee Felsenstein's Expander User's Manual

This lot has closed

Estimate: $600+


Expander user's manual from the collection of personal computer pioneer Lee Felsenstein, an original member of the Homebrew Computer Club who designed multiple important early computers: the Intel 8080-based Sol-20, the first fully assembled microcomputer with a built-in keyboard and television output; and the Osborne 1, the first mass-produced portable computer. This manual derives from his work on the Expander, built by Micro-Expander Inc., a 'slimline' computer with a built-in keyboard and number pad, measuring about 18 inches square and 4 inches thick. The system ran on a Z80A (3.58 MHz) processor, with 64K of RAM, color video output, and S-100 expansion bus (hence the name 'Expander').

Felsenstein was originally recruited to the Expander project by Micro-Expander's president, Mats Ingemanson, a young Swedish gentleman who wished to develop a personal computer to be sold in Europe. Felsenstein was able to build a working prototype of the Expander before his responsibilities as a founding member of the Osborne Computer Corporation became his chief priority. He turned over the Expander work to Robert Marsh, former VP of Processor Technology, to bring the design to a manufacturable level. Although some 200 Expander computers were built by Manu-Tronics Corporation of Kenosha, WI, Ingemanson was able to pay for only 10 and the rest had to be scrapped. Thus, only ten Expander computers got into buyers’ hands—the computers and their associated documentation are therefore extremely rare.

In fine condition, with light general wear.

Auction Info

  • Auction Title: Science and Technology
  • Dates: #650 - Ended December 15, 2022