K850
1203-2528 rev. 1
TROUBLESHOOTING
Key Problems
TROU
B
L
E
S
H
O
OTIN
G
Yes
Problem with
Phone On
Perform Diode
Measurement
Connect the
black probe to
MP PBA GND. More than
2.0 Volt DC at
MP 127 (S2400 A)
Press the On/Off
key S2400
Yes
0 Volt DC at
MP 127 (S2400 A)
Replace
S2400
No
SL 5 Replace
N2000
SL 4 Scrap
Yes
Remove
S2400
No
More than
2.0 Volt DC at
MP 127 (S2400 A)
No
Replace
S2400
Yes
Problem with
Phone Off
Replace
V2402
No
Yes
Problem with
Volume Down
key
No
More than
2.0 Volt DC between
MP 134 (S2402 A) and
MP 135 (S2402) C
Yes
Press the
Volume Down key
S2402
Yes
0 Volt DC
between
MP 134 (S2402 A) and
MP 135 (S2402 C)
SL 5 Replace
D2000
SL 4 Scrap
Yes
Replace
S2402
No
Short circuit
between
MP 135 (S2402 C) and
MP PBA GND
No
Remove
S2402
SL 5 Replace
V2478
SL 4 Scrap
Yes
No
More than
2.0 Volt DC between
MP 134 (S2402 A) and
MP 135 (S2402 C)
No
Yes
Problem with
Volume Up
key
No
More than
2.0 Volt DC between
MP 132 (S2403 A) and
MP 131 (S2403 C)
Yes
Short circuit
between
MP 131 (S2403 C) and
MP PBA GND
No
SL 5 Replace
V2477
SL 4 Scrap
Yes
Remove
S2403
More than
2.0 Volt DC between
MP 132 (S2403 A) and
MP 131 (S2403 C)
No
SL 5 Replace
D2000
SL 4 Scrap
No
Replace
S2403
Yes
Press the
Volume Up key
S2403
Yes
0 Volt DC
between
MP 132 (S2403 A) and
MP 131 (S2403 C)
Problem
With all other
keys
No
Replace
X2410
Yes
Problem
solved
SL 5 Replace
D2000
SL 4 Scrap
Yes
No
No
Claim
X2410
Yes
Replace
S2402
SL 5 Replace
D2000
SL 4 Scrap
START
Step 1:
Use TRS Fixture and connect Display and
Keypad. Connect: VBATT
Perform Keyboard Test in Service Tests
If All Keys working properly at the
TRS Fixture then replace Keypad. If not then
disconnect VBATT and continue with the
Key problems TRS guide
Key problems
START
Load ITP SW into the phone.
Use TRS Fixture
Connect: VBATT and DCIO/SEPI
Use Fault Trace SW
On Red LED
problems:
Use Fault Trace SW
MMI
LED and Backlight
Activate:
Red LED
More than
1.8 Volt DC at
MP 128 (C2427)
SL 5 Replace
N2000
SL 4 Scrap
No
Replace
V2428 Red LED
Yes
On Keypad LED
problems:
Connect Keypad
Use Fault trace SW
MMI
LED and Backlight
Activate:
Keypad Backlight
If Keypad LED works
properly at the
TRS Fixture then replace
Keypad
Problem with all
Keypad LED
rows
4.5 Volt DC
at
MP 18 (TP4112)
Yes
Replace
N4101
Yes
Replace
X2410
No
No
Replace
X2410
Connect Keyflex to
the PBA
Use Fault trace SW
MMI
LED and Backlight
Activate:
Camera Keypad LED
More than
0.8 Volt DC at
MP 162 (R4114)
MP 164 (R4115)
MP 163 (R4116)
Keypad LEDs
Ok
SL 5 Replace
N2000
SL 4 Scrap
No
Claim Component
X2410
Yes
Replace
N4101
Yes
Replace
X2410
No
Camera Light Ring
problems:
Connect Single
Flash Assembly to
PBA
Use Fault trace SW
MMI
LED and Backlight
Activate:
Camera Light Ring
1.8 Volt DC
at
MP 20 (TP4106
AF_LED)
Yes
No
Connect Single
Flash Assembly to
PBA
Use Fault trace SW
MMI
LED and Backlight
Activate:
Autofocus LED
Replace
X2511
Replace
N4101
Problem with any
of the Keypad LED
rows
Yes
No
Problem with
Camera Keypad
LED
Yes
Problem with
Autofocus LED
No
Yes
No
More than
1.2 Volt DC
at MP 30 (R2544
LED_BACK)
SL 5 Replace
N2000
SL 4 Scrap
Yes
No
Replace
X2511
LED problems
/ LED Problems
SEMC Troubleshooting Manual
11
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