I recently changed the rifa cap on my old Apple IIe and after putting everything back together my duodisk drive is constantly spinning and has a red light on at all times.
I am pretty new to this, so I am not sure what the issue could be. Before changing the rifa everything worked fine.
Could be either the controller card (most likely) or the drive unit. Check the LS259, LS132, or NE566 in that order.
The devil is often in the details of just how you went about "changing the RIFA capacitor ...and putting everything back together."
Sounds like your description may have left out some details. The RIFA, for several reasons, should not have any noticable effect on what you described. You got any pictures of your board after you did you rifa replacement? Top and bottomr and or installed in the supply enclosure?
What type of drive is this? is it a Disk II or the plastic 5.25 disk? My guess would be the Disk II and when reworking you may have disconnected the disk drive ribbon cable from the controller card. If that's correct there's a chance you may have reassembled the ribbon cable to card wrong. If that happened there's a very lkely suspect or two on the control board inside the drive itself.
If you have the plastic drive with the DB-19 connector there's likely something else....