IBM 7940, Problem Determination And Service Manual

Page: 111 / 160

v Follow the suggested actions in the order in which they are listed in the Action column until the problem
is solved.
v
See Chapter 3, “Parts listing, Type 7940 and 7941 servers,” on page 19 to determine which components
are customer replaceable units (CRU) and which components are field replaceable units (FRU).
v If an action step is preceded by “(Trained service technician only),” that step must be performed only by a
trained service technician.
Symptom Action
The monitor has screen jitter, or
the screen image is wavy,
unreadable, rolling, or distorted.
1. If the monitor self-tests show the that monitor is working correctly, consider the
location of the monitor. Magnetic fields around other devices (such as
transformers, appliances, fluorescent lights, and other monitors) can cause
screen jitter or wavy, unreadable, rolling, or distorted screen images. If this
happens, turn off the monitor.
Attention: Moving a color monitor while it is turned on might cause screen
discoloration.
Move the device and the monitor at least 305 mm (12 in.) apart, and turn on
the monitor.
Notes:
a. To prevent diskette drive read/write errors, make sure that the distance
between the monitor and any external diskette drive is at least 76 mm (3
in.).
b. Non-IBM monitor cables might cause unpredictable problems.
2. Reseat the monitor cable.
3. Replace the following components one at a time, in the order shown, restarting
the server each time:
a. Monitor cable
b. Monitor
c. (Trained service technician only) System board
Wrong characters appear on the
screen.
1. If the wrong language is displayed, update the BIOS code (see “Updating the
firmware” on page 15) with the correct language.
2. Reseat the monitor cable.
3. Replace the following components one at a time, in the order shown, restarting
the server each time:
a. Monitor
b. (Trained service technician only) System board
Chapter 5. Diagnostics
93