IBM 5140 - Documentation Pointers
"An Introduction to the PC Convertible"
Pages 1110-1115 (PDF pages 1142-1147) of Upgrading and Repairing PCs - Tenth Anniversary Edition
IBM manual - 'Technical Reference'
There is a link to the technical reference here.
There is a lot of good technical information on the IBM 5140 page at ohlandl.ipv7.net; a link to that page is here.