Motorola 880, Service Manual

Page: 47 / 171

12/9/97 68P09403A50 39
Troubleshooting
1. Unit Doesn’t
Turn On or
Stay On c) Defective RF/Audio-Logic
Board assembly. 1. Gain access to Keypad/Display / main
board as described in “Disassembly” on
page 29.
2. Remove the Logic/RF Assembly. Substitute
a known good assembly.
3. Temporarily connect a +6 V dc supply to the
battery connectors as shown below.
4. Depress the PWR button; if unit turns on
and stays on, disconnect the dc power
source and reassemble the telephone with
the new Logic/RF Board assembly and
refer to “GSMTesting After Repair” on
page 35.
5. If Logic/RF Board Assembly is not at fault,
re-install original Logic/RF Board Assembly
and proceed to d.
d) Keypad/Display circuit
board failure. 1. Replace the Keypad/Display board.
2. Temporarily connect a +6 V dc supply to the
battery connectors as shown above.
3. Depress the PWR button; if unit turns on
and stays on, disconnect the dc power
source and reassemble the telephone with
the new Keypad/Display board.
2. Display is
erratic, or
provides
partial or no
display. a) Mating connections to/from
Keypad/Display board
faulty. 1. Gain access to Keypad/Display / main
board as described in “Disassembly” on
page 29. If connections are faulty then
replace the connector(s) as necessary.
2. If connections are not at fault proceed to b.
b) Keypad/Display board
defective. 1. Substitute a known good Keypad/Display
circuit board. If known board works, the
original is faulty and should be examined for
improper solder and/or connections. Likely
fail components: J500.
Table 8: GSM Logic/Processing Troubleshooting and Repair Chart
Logic/Processing
Symptom
Probable Cause Verification and Remedy
J600
LOGIC/RF BOARD
(PARTIAL VIEW)
+6V
GND
Battery
Connectors
Accessory
Connector