Terrors; Derrors - HP 7936 Support Manual

Troubleshooting and Diagnostics
7936 and 7937
NOTE
It is very important to note that when
HDA A3 is called out as one of the
most likely failing components in the
drive, care should be taken to prove that
the actua I media, electronics, or
mechanics is defective in the HDA. The
HDA is the most expensive assembly in
the drive and the most difficult assemb-
ly to replace. Be sure it requires
replacement before doing so. In many
cases, simple magnetic recording
problems on the disc surface
rna
y be the
problem. For example, a defective
read/write PCA may have caused data
destruction on the surface of the disc,
which appears as a hard fault when
reading. Simply replacing the R/W PCA
and rewriting the suspect sectors will
correct the problem. Refer to para-
graph 8-19 for more details regarding
da ta error related faults.
The drive errors are divided into two classifica-
tions: Test Errors (TERROR) and Drive Errors
(DERROR). The classification of each error is
determined by when the error occurred.
8-16.
TERRORS
A TERROR is defined as an error that occurred
during execution of the drive's self-test diagnostics,
regardless of whether the diagnostics were invoked
at power-on or by the host. When retrieving drive
status following a diagnostic failure, each
TERROR will be accompanied by a Field
Replaceable Unit (FRU) code. The FRU identifies
the most likely cause of the failure. In the
DESCRIPTION column of table 8-2, the failing as-
sembly is identified for those error codes which
may be returned as TERRORS. If no assembly is
indicated, the drive is unable to accurately isolate
the malfunctioning hardware (FR U code =
0).
TERRORs are also logged in the fault log;
however, the accompanying FRU code is not
recorded.
It should be understood that the FRU numbers do
not necessarily correspond to the drive assembly
8-6
numbers documented in this manual. The
following matrix shows the relationship of the
FRU numbers to the assembly numbers and the as-
sembly names. Note that four of the drive as-
semblies, including head-disc assembly A3, do not
have FRU numbers.
FRU
o
2
3
4
S
DRIVE ASSEMBLY
None - unable to isolate
malfunctioning hardware
Controller PCA-A6
Read/Write PCA-A2
Servo PCA-A1
Power Supply PCA-A4
Spindle Motor B1
Head-Disc Assembly A3
Power Distribution PCA-AS
LED PCA-A?
Primary Power PCA-A8
8-17. DERRORS
Errors that occur during any drive activity other
than self-test diagnostics are classified as
DERRORs. The DERRORs, which are logged in
both the drive status and the fault log, can be ac-
cessed using the appropriate external exerciser
command.
The DERROR codes define a specific drive mal-
function that occurred during routine drive opera-
tion. If the same malfunction occurred during self-
test diagnostics, it would classified as a TERROR;
therefore, certain error codes may fall into either
category.
8-18. SERVO CONTROLLER ERROR
CODES
Errors that are generated by the servo controller
(see the servo flowcharts in chapter 5) are mapped
into different error codes by controller PCA-A6
before being logged in the fault log. The following
matrix allows the servo controller error codes to
be converted to their corresponding
TERROR/DERROR codes.