Apple IIe I/O error Troubles

[classacom@ibm.net]

Having had my Apple IIe since 1983, it's really become a member of the
family...but unfortunately now it's sick.  

Long ago I upgraded the unit so it was the "enhanced" version.  It has 3
floppy drives... 2 - drives that are the 2 Disk ][ models(In slot 6) and
1 - which I use the most is the UniDisk 3.5 model -- in slot #5.

I also have a 8 Mghz "Zip" chip and a 1 Meg of ram via a Ramworks card.

I first thought my UniDisk 3.5 was suddenly malfunctioning, but on
trying to boot off the Disk ][ in slot six, I get the same message.  I/O
error.  All connections on drives have been checked

I am guessing I apparently have a chip that's bad, but have no idea
where to begin in order to resolve this problem. 

 Suggestions?  Any help would be most appreciated.

Thanks 

Jay F.