I can't find A schematics at the moment either, but here's a link to a document that tells you how to convert your A to a B ... I posted this on one of the first pages of this thread, but the original link has gone stale:


And this technical manual http://www.os2site.com/sw/DEC/rainbow/doc2/pc100tm1.pdf also seems to talk about the "A" model.

NCR DMV- DEC Rainbow- Siemens PCD- ITT 3030-Oly People- Acorn A5000- Olivetti M20