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6. Open the LCD half-way, then stand the computer on
its front edges so that the suspend switch is not
activated.
7. Power-on the computer.
8. Check the voltages of the voltage converter on the
system board. See the following figure.
Notes:
a. Make sure the suspend switch (located to the left
above the keyboard) is not activated during
measurement of the voltage.
b. Only PG is marked on the system board. Use
the following figure to locate the VA, VG, VB,
VA3, and VB3 signal names.
PG
Ground
VG
VB3
VA3
VA
VB
If any voltage is not correct, go to step 9.
If all voltages are correct, the voltage converter
is operating correctly. If the power problem did
no reoccur, reconnect the devices removed in
step 2 to isolate a device problem.
If all the voltages are correct and the power
problem still exists, replace the following FRUs
one by one.
– System board
– Processor card
9. Power-off the computer and unplug the AC adapter
cable from the computer.
10. Check for a short circuit between Ground and VA,
VG, VB, VA3 or VB3. The following table shows
which FRUs can cause a short at each signal.
Signal V dc Min. V dc Max.
VA +4.75 +5.25
VG +4.75 +5.25
VB +4.75 +5.25
VA3 +3.42 +3.78
VB3 +3.42 +3.78
PG +4.00 +5.25
ThinkPad 700, 700C, 720, 720C (9552) 79