This was a "hobby" project by Gordon Anderson, that attracted a fair sized following of radio builders who used his main board design to upgrade their old Ace Micropro 8000 transmitters, as well as many other brands. It was "freeware", although the software was not "open source". The capabilities are still on a par (and sometimes better) than the current line of OpenTX transmitters (Taranis, etc.). Mr. Anderson sold the unpopulated boards at cost, and it was up to the purchaser to find all the components and assemble via his excellent instructions. There were at least two major versions of main boards, using different "processors". More information can be found here:
MicroStar 2000 Note that some of the information has become a bit dated, as some of the contacts are no longer with us. But Gordon's e-mail (listed) should still work. There is also a Microstar Yahoo! users group that still has some activity. I wrote a supplemental "how to use" manual for it, for one of the earlier versions. For "debugging" the hardware, the first order would be to determine which version you have. If the most recent, then there should be full schematics available, likely on the web site. Gordon will have the same for the earlier version. Radio South (Tony Stillman) has done some repairs in the past on these radios, so may be a source of information, also.