I have my inch thick 3000T A4 Service Manual here dated July 91. It is obviously for a stock 3000T though expansions are discussed. Nothing appears to discuss your issue though I will have a further look.
Probably not related, but, I have two A3000Ts and have taken the battery off both. I don't use either though a comment was made when I did this that the battery did serve some functionality other than a clock. I have no idea to be honest, I was more worried about battery damage. Just a thought.... thinking about where data maybe stored to keep the system operational. Others would know better.
When I get some time I may scan the manual and stick it on the website.
Good luck.
