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 lef 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.

Ground

PG

VA3

VB3

VB

VA

VG

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

 

 

 

 

 

 

 

 

Ÿ

If

any

voltage is

not

correct, go to step 9.

Ÿ

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.

ŸIf 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.

 

ThinkPad

700,

700C,

720,

720C

(9552)79