Zenith Z-100 PC series Service Manual page 290

Page
4.4
Troubleshooting
Floppy Disk Controller
Floppy disk systems can exhibit a number of symptoms that can be traced
to poor or bad disks, dirty or misaligned disk drive heads, or improper
user operation. As a result of any of these problems, several different
error messages can be generated by either the computer firmware (ROM)
or operating system software. You should be familiar with normal disk
operation in computers before attempting to service this section of the
floppy disk controller card.
The following quick checks should isolate the problem to the card, disk
drive, or other parts of the computer system.
1. On normal power up, check the CPU diagnostic lights (LEOs) for
proper sequencing.
• With autoboot switched off (see CPU card switch settings), the
OSK light on the CPU card should be the last light to go out
(except for the ROY light, which will remain lit until a disk has
been successfully booted).
• With autoboot switched on (floppy disk boot), the OSK light will
remain on until a disk is inserted. Otherwise, an error message
will be generated, which reads:
+ + +
DISK ERROR: DRIVE NOT READY!
+ + +
This is a normal error message and indicates that a bootable disk
has not been placed in the disk drive. Timing of the timeout is con­
trolled by the ROMs on the CPU card. Therefore, if you get this
error message immediately after resetting the computer by pressing
the CTRL, AL T, and DEL keys at the same time, you should check
the ROM on the CPU card.
Other conditions that can cause this error message include disk
improperly placed in the drive and drive door (latch) not closed.
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