HP 7925D Service Manual page 78

TroUbleshooting
Table 4-1. Visual Indication of Drive Status (Continued)
7925
ACTIVE STATE
INDICATOR!
FUNCTIONAL
INDICATION
DIAGRAM
LOGIC EQUATION CIRCUIT DESCRIPTION
DRIVE FAULT f.
Non-destructive write fault, caused by one of the
Indicator
following:
(Continued)
1. Heads not settled on a cylinder [ACRY (Access
Ready) signal inactive] while in write mode. (W •
AR LED indicator is lit.)
2. Drive in both read and write mode at the same
time. (R • W LED indicator is lit.)
IL LED Indicator
- - -
Indicator is lit when one of the following conditions is met: Fault Detection
Any PCA (with the exception of PCA-A11 and PCA-
System, figure 4-29.
a.
A12) not firmly seated or correctly positioned in the
drive.
b. Pack loading assembly disconnected.
c. +36 Vdc, +12 Vdc, +5 Vdc, -12 Vdc, -24 Vdc, or
-36 Vdc power source out of tolerance or missing.
d. Temperature of heat sink on PCA-A9 rises above a
specified limit.
e. A spindle fault is detected.
AGC LED
AG~
DRDY
=
AGC Indicator is lit when the following conditions are met: Fault Detection
Indicator • SKH • DRDY
Heads are out of cylinder area between inner and
System, figure 4-29.
a.
outer guard bands. [DRDY (Drive Ready) signal
active.]
b. AGC (Automatic Gain Control) and DRDY (Drive
Ready) signals active.
CB LED CRB. DRDY
Indicator is lit when the following conditions are met:
Fault Detection
Indicator
CRB (Carriage Back) signal active.
System, figure 4-29.
a.
b. DRDY (Drive Ready) signal active.
MH LED Indicator MHS + WRITE. DCW Indicator is lit when more than one head is selected for
Fault Detection
reading or writing. System, figure 4-29.
W. AC and MH WRITE. DCW Both indicators are lit when the following conditions are
Fault Detection
LED Indicators met:
System, figure 4-29.
a. DC current supplied to head drivers.
b. Drive not in write mode.
T LED Indicator TOFL
Indicator is lit when one of the following conditions is met: Fault Detection
Heads not settled on specified cylinder within 120
System, figure 4-29.
a.
milliseconds after SK (Seek) signal is activated.
b. Heads not settled on cylinder 0 within 1667 millisec-
onds after SKH (Seek Home) signal becomes active.
c. Heads do not reach fully retracted position within 1667
milliseconds after RET (Retrack) signal becomes
active.
d. Heads not settled on cylinder 0 within 1667 milli-
seconds after RH (Restore Home) signal becomes
active.
4-4