There's a full scan of my printed A3000 service manual freely available on my webserver
schematics page.
If you've already looked at that, get it again as I just replaced the PDF with my original scans. Cosmos offered to clean and compress them for me a couple of years ago, which in this case resulted in loss of detail and a compression from 3.8MB to 14.7MB (WTF?!). Must go through and compare the rest of my scans and Cosmos' cleaned versions and keep the better of the two.
If you're after a 'diagnostic manual', I've never seen such a thing for the A3000. There's an A500 service training guide
here which gives some insight, but realistically it's not easy or practical to produce a guide to magically diagnose every conceivable fault for such a relatively complex machine. Besides, it keeps electronics engineers such as myself employed
If you get stuck with it, contact me for a repair estimate. I have a collection of instruments and in circuit hardware debuggers for fault tracing and repair to more depth than the basic checks you can do yourself.
