Amazing find for the #zxspectrum community. Design documents for the ULAs of several Sinclair products have been found and archived. As well as schematics for some Spectrum models and more technical documentation and communication:
https://www.youtube.com/watch?v=jiW3P1rJRMc
EDIT: Would be nice if someone mirrored this on archive.org or somewhere other than Google Drive. :)
