I have a Sider external disk drive that I can run in slot 7 if I remove the disk II control card from the expansion slot 6. I know I used to be able to leave the card in the computer and everything ran fine. Now I can't even leave the card in the slot with the sider cable connection disconnected. The disk drives stop working.
Any ideas?
The most common failure on Sider drives is the power supply in the drive unit itself. Can you try the controller in slot 5, boot from floppy in 6 and try running the Sider utility software?
You didn't mention it was a IIgs. What is your control panel settings for the card slots? Make sure you have whatever slot the Sider controller card in set to "your card".