IBM Thinkpad T20 T21 T22 T23 Manual

Intermittent problems
Intermittent system hang problems can be due to a variety
of causes that have nothing to do with a hardware defect,
such as cosmic radiation, electrostatic discharge, or
software errors. FRU replacement should be considered
only when a problem recurs.
When analyzing an intermittent problem, do the following:
1. Run the diagnostic test for the system board in loop
modeat least 10 times.
2. If no error is detected, donotreplace any FRUs.
3. If any error is detected, replace the FRU...

FRU replacement notices
This section contains notices related to removing and
replacing parts. Read this section carefully before replacing
any FRU.
Screw notices
Loose screws can cause a reliability problem. In IBM
ThinkPad computer, this problem is addressed with special
nylon-coated screws that have the following characteristics:
vThey maintain tight connections.
vThey do not easily come loose, even with shock or
vibration.
vThey are harder to tighten.
vThey should be used only once.
Do the following...

vMake sure you use the correct screw. If you have a
torque screwdriver, tighten all screws firmly to the torque
shown in the table.Never use a screw that you
removed. Use a new one. Make sure the screws are
tightened firmly.
Retaining serial numbers
This section includes the following descriptions:
v“Restoring the serial number of the system unit”
v“Retaining the UUID”
Restoring the serial number of the system
unit
When the computer was manufactured, the EEPROM on
the system board was loaded with the...

and stored in the EEPROM of your system board. The
algorithm that generates the number is designed to provide
unique IDs until the year A.D. 3400. No two computers in
the world have the same number.
When you replace the system board, you must set the
UUID on the new system board as follows:
1. Install the ThinkPad hardware maintenance diskette
version 1.62, and restart the computer.
2. From the main menu, select4. Assign UUID.
A new UUID is created and written. If a valid UUID
already exists, it is not...

Removing and replacing a FRU
This section presents directions and drawings for use in
removing and replacing a FRU. Be sure to observe the
following general rules:
1. Do not try to service any computer unless you have
been trained and certified. An untrained person runs
the risk of damaging parts.
2. Before replacing any FRU, review“FRU replacement
notices”on page 56.
3. Begin by removing any FRUs that have to be removed
before the failing FRU. Any such FRUs are listed at the
top of the page. Remove them...

1010 Battery pack
DANGER
1
2
Use only the battery in the parts listing for your
computer. Use of an incorrect battery can result in
ignition or explosion of the battery.
Removing and replacing a FRU
60ThinkPad T20, T21, T22, T23 (MT 2647/2648) 

1020 Backup battery
DANGER
For access, remove this FRU:
v“1010 Battery pack”on page 60
1
2
Step Screw (quantity) Torque

1M2.5×3.5 mm, (1) 0.392 Nm
(4 kgfcm)
(continued)Use only the battery in the parts listing for your
computer. Use of an incorrect battery can result in
ignition or explosion of the battery.
Removing and replacing a FRU
ThinkPad T20, T21, T22 and T23 series61 

Cable routing:When attaching the backup battery to the
holder, route the battery cable as in the
following figure.
Removing and replacing a FRU
62ThinkPad T20, T21, T22, T23 (MT 2647/2648) 

1030 Hard-disk drive
AttentionDo not drop or apply any shock to the hard-disk
drive.The hard-disk drive is sensitive to physical
shock. Incorrect handling can cause damage and
permanent loss of data.
Before removing the drive, have the user make a
backup copy of all the information on the drive if
possible.
Never remove the drive while the system is
operating or is in suspend mode.
For access, remove this FRU:
v“1010 Battery pack”on page 60
1
Note:The hard disk is attached to the cover.
Step Screw...

When removing the hard-disk drive, open the LCD a little
as shown in the figure.
2
3
3
4
When installing:Make sure that the HDD connector is
firmly connected.
Removing and replacing a FRU
64ThinkPad T20, T21, T22, T23 (MT 2647/2648)