HP 16500A, Service Manual, Page: 76 / 144

Touchscreen Test
The Touchscreen Test checks for light pulses
between LED (light emitting diode) pairs and
returns a pass, fail or an impair message.
The impair message indicates that the
touchscreen is faulty, but the instrument can still
be operated. If two to four LED pairs of the
touchscreen system are defective, then the impair
message is displayed. The touchscreen can still
be used to operate the instrument, except for the
touch-sensitive areas controlled by the faulty LED
pairs.
The fail message indicates that the touchscreen is
faulty and cannot be used to operate the
instrument. The fail message is displayed if five or
more LED pairs of the touchscreen system are
defective. If the Touchscreen Test fails, you can
still operate the instrument by using a mouse.
If a mouse is connected and the Touchscreen
Test fails (meaning there are five or more
defective LED pairs), then the impair message is
displayed instead of the fail message and the
mouse can be used to operate the instrument. To
obtain true Touchscreen Test results, disconnect
the mouse before performing the test.
For Touchscreen Test failures, clean the screen
and the surrounding area and move any objects
blocking the screen at power-up. Verify the
continuity and connection of the cable from the
microprocessor board to the front-panel board.
If a problem is not found with the cable and the
Touchscreen Test still fails after cleaning the
instrument, suspect a faulty front-panel board.
Front and Rear Disk Tests
The Disk Tests read each disk to identify the
format. If the format cannot be identified, the test
is considered to have failed for that disk drive. If a
disk cannot be detected, the message "no disk" is
displayed instead of the pass or fail message.
This power-up disk test only checks a few tracks.
Possible problems causing a fail message include
the following:
A damaged or disconnected disk drive cable.
Wrong disk formatting or no disk formatting.
Incorrect position of the address switch on the
disk drive.
A faulty disk drive.
Faulty microprocessor interface circuitry to the
disk drive.
For Disk Test failures, verify the continuity and
connection of the disk drive cables and use
formatted disks. The address switch on each disk
drive is set to the correct position when the disk
drive is installed at Hewlett-Packard. A failure will
occur if the switch on a replacement disk drive
assembly is set to the incorrect position. For the
correct switch position, refer to section 6-16,
"Front Disk Drive Replacement," or to section
6-15, "Rear Disk Drive Replacement."
If the Disk Test still fails after verifying that the
previous items are not causing failures, refer to
section 6-7, "Troubleshooting."
HP 16500A/16501A - Service
6-7