In the Tandy forum there is a thread that is searching for how to resurrect a Tandy 1400HD, once the PSU has failed. One of the chief issues is that there is no schematic or service manual for the Tandy 1400HD and that these have little to no similarity with the Tandy 1400FD or 1400LT.

While perusing old copies of Portable 100 (Oct 1989, p19) the writer mentioned that the Tandy 1400 HD appears to be related to the Grid 140XT and that it was from Sanyo. Are there any Grid 140XT owners out there? Are these two similar on the inside? Is there any schematics/service manual/ other information for the Grid 140 XT, since it might also be applicable to the Tandy 1400HD?