I have not done Apple II/II+ repairs in years but try the following Diags:
1) Like Jack stated, remove the Disk II card out the Apple and turn it on. It should Boot to BASIC with ']' and a flashing cursor.
2) Type. does the keyboard work? With the cover open feel the bottom rear of the keyboard, some of them have a switch on them, I believe this is for a Uppercase/lower case option, but not all Apples have them, just some. if the switch is there, slide it and try it.
2a) Check the keyboard ribbon cable. It should be a 16 flat wire cable with an IC Header on both sides. Make sure it is firmly seated in the sockets; one sock will be at the keyboard and hard to get too without unscrewing the case off the bottom panel... Check if the headers have all their pins. A loose or broken pin can create problems.
3) Assuming that the keyboard is fine or fixed, Look at the cable on the drive header on the drive card. Make sure all the pins are in the cable's socket. Off by a pin left or right or off by a row will cause problems and can even kill a drive! Look at the chips on the cards, are they OK looking (no cracks or bulges).
4) Assuming that the card is OK, open the drive. Take the cover off, and flip it over. See the motor spindle, drive belt and Disk Spindle (Large wheel with B/W pattern)? Does the motor spin with the Apple is turned on? Does the belt has some flex to it? Does the Spindle spin? There's a whole lot of other things to look at, and even adjust the speed of the hard drive from here but lets assume all this is fine and working...
5) Move the head to the spindle. and turn on the Apple. Does it move back? Inspect the arm above the head, does it have a cotton pad on it? Does it sit firmly on the head?
6) Check the chips on the controller board. They look OK? With the exception of 2, they are all 74LS series chips and easy to replace.
This is a simple diagnostics, everything else from here is just too detailed to list here. I could add more later.
At best, you may have to remove the boards and wiggle the chips on the sockets to clear the corrosion that has built up on them. At worst, you may need a new Disk ][ Card and Disk Drive. I forget which chip on the Disk ][ card that short out that kills disk drives, but that is fixable with replacing that chip on the Disk ][ card and all the 74LS chips on the Drive.
Edited by Elfen, 12 November 2017 - 07:08 AM.
Amassed a collection of various Macs and PCs that friends are calling my place a Mac museum: 512Ke, Plus, SE/30, IIcx, IIci, Q950, Q800, Q8100, 7100, Biege G3, PB 5300ce,190, 190c, 150, 180, (4) Duo 210, Duo 230, (2) 250, 280, 280c, 2300c, (3) G3 Wallstreet, iBook G3 (Orange), (3) iBook G3 (White), (3) iBook G4, PB G4 (all 12in)