I created a Factory Set of all sounds for the Roland D-20. I'm no longer a D-20 owner, but I had one for quite a long time, and have learned a lot about keeping one working and functioning as you can see in the archived posts related to it.
The downloadable SysEx file is the original factory sounds and settings for the D-20 from Roland. A lot of users lose these when they reinstall batteries or have a freeze or any problem. Sometimes people also tweak the sounds so much they lost the originals and are unable to get them back to where they used to be. Please note that you will need some sort of SysEx libary/MIDI library program to get the files from your computer to the synthesizer.
I've also got a PDF of the E-Mu Proteus 2500 Command Station manual. This is my current synthesizer that I use, in addition to the synths in Logic. It's not impossible to find, but it isn't out in plain sight on the web, either. I figure I'll put a link to it here on the site to make it a little easier to find out there on the interwebs.