Visual Indication Of Drive Status - HP 7925D Service Manual

PART IV - TROUBLESHOOTING
The troubleshooting information provided in section IV of
the main manual requires a number of changes and addi-
tions to make it applicable to the HP 7925H. Changes are
required for the following:
• Diagnostic Test Programs (paragraph 4-1)
• Troubleshooting Flowcharts (paragraph 4-2)
• Power Sources (paragraph 4-3)
• Visual Indication of Drive Status (paragraph 4-4)
• Disc Service Unit (paragraph 4-5)
• System Functional Diagrams (paragraph 4-6)
• Wiring Connections (paragraph 4-7)
• Power Distribution (paragraph 4-8)
Details of the required changes are provided in para-
graphs A-76 through A-88.
WARNING
Troubleshooting instructions are in-
tended for service-trained personnel
only. To avoid potentially serious
electrical shock, do not proceed
further in this part unless qualified
to do so.
A-76. DIAGNOSTIC TEST
PROGRAMS
In addition to employing the diagnostic test programs de-
scribed in the main manual, the HP 7925H also includes a
self-test capability that assists in isolating certain mal-
functions to the printed-circuit assemblies (PCA's) and
other components of the disc drive. Details of this self-test
feature are provided in the following paragraphs.
A-77. SELF TEST
Self test thoroughly tests controller PCA's Al and A2 to a
functional block level (110 logic, microprocessor,
formatter/separator, etc.) and is intended as an aid to
board-level repair of the controller. Certain functions of
the disc drive are also tested on a go/no-go basis. The
self-test feature includes the following components:
• Test firmware in ROM.
• A test panel with operating controls and indicators,
located at the rear of the disc drive (see figure A-12).
• A SELF TEST FAILED indicator on the operator
panel of the disc drive.
The self-test routine is divided into 13 separate tests with
two additional tests reserved for equipment adjustments.
Most of the tests are subdivided into sections (up to 15).
The tests are executed in a "bottom up" progression, first
testing the controller microprocessor, extending to the
remainder of the controller logic, and finally testing the
functioning of the disc drive (with the exception of write).
The tests are executed in reverse order, from test 17 (octal)
to test 3. The first test turns on all of the rear panel TEST
RESULT LED's (octal 17). If self test passes, all of the
LED's are turned off.
Self test can be invoked in the following three ways:
• Automatically via a power-on or by setting the disc
drive RUN/STOP switch to RUN.
• Using the secondary HP-IB INITIATE SELF-TEST
command.
• Manually by activating the START switch on the rear
self-test panel (assuming that the controller is in Idle
State 2 or 3).
Note: The LED in the upper left-hand corner of
the disc drive Unit Select Indicator is
unlighted when the controller is in Idle
State 2, Idle State 3, or when self test is
running. When the LED is lighted, the
controller will not respond to the test
START switch.
A-78. MODES OF OPERATION
The OP/SERVICE switch on the self-test panel (figure
A-12) places the controller self-test feature in either an
operating mode or a service mode. The switch must be in
the OP (operating) position for the disc drive to operate
normally. In the SERVICE position, the self-test circuit
will loop continuously in self-test until a failure occurs.
Details of the two modes of operation are provided in the
following paragraphs. Refer to table A-7 for a summary of
self-test control operation and to table A-8 for a detailed
description of the tests.
A-37