C1 on the 1984 Mac 128k's analog board is different than what you will find on an SE/30's analog board. As such, you need to replace C1 on older 128k and 512k Macs but you do not on the SE/30.
As to your drive, you probably just need to clean the heads. If that doesn't work, it could be in need of lubrication. If that doesn't work, check the cable -- a lot of drive problems result from the cable either being bad or not plugged in well. If that doesn't work, then be sure that the logic board and all internal parts are clean. Gunk on electronics causes crazy things to happen. If that doesn't work, then you are likely in need of a new drive. I've purchased one such drive from WeLoveMacs in the past, but they do cost more than EBAY:
http://www.welovemacs.com/6610345.html
As to your drive, you probably just need to clean the heads. If that doesn't work, it could be in need of lubrication. If that doesn't work, check the cable -- a lot of drive problems result from the cable either being bad or not plugged in well. If that doesn't work, then be sure that the logic board and all internal parts are clean. Gunk on electronics causes crazy things to happen. If that doesn't work, then you are likely in need of a new drive. I've purchased one such drive from WeLoveMacs in the past, but they do cost more than EBAY:
http://www.welovemacs.com/6610345.html