I love my HP9815A and take a good care of it but recently it got into problems and needs repair. Please let me know where to buy manual and schematics (and service manual if any available).
Agoo
A DVD with the manuals you asked about is available here.
The HP9815 service manual does not include full schematics (I think you get scheamtics of the low-voltage PSU, but nothing more).
There is an unofficial reverse-engineered schematic on the HPCC CD-ROM, it's also available to download (along with the HP user and service manuals) from the Australian museum site.
I am not sure if I can mention the URLs of those sites here, if you can't find them, contact me.