Motorola 880 Service Manual page 48

Dual Band 880/890 (DCS/GSM)
Table 8: GSM Logic/Processing Troubleshooting and Repair Chart
Logic/Processing
Symptom
2. Display is
erratic, or
provides
partial or no
display.
3. Incoming call
alert trans-
ducer audio
distorted or
volume is too
low.
40
Probable Cause
c) Logic/RF Board Assembly
defective.
a) Connections to/from
Keypad/Display circuit
board faulty.
b) Alert transducer defective.
c) Keypad/Display board
assembly defective.
d) Logic/RF Board Assembly
defective.
68P09403A50
Verification and Remedy
1. Substitute a known
Assembly.
2. If known assembly works, the original is
faulty and should be examined for improper
solder and/or connections. Likely fail
components: J500, Q101, Q104, Q107, and
U701.
1. Gain access to Keypad/Display board as
described in "Disassembly" on page 29.
2. Check connection from alert transducer and
from the Keypad/Display board to the Logic/
RF assembly.
3. If connection not at fault, proceed to b.
1. Gain access to alert speaker as described
in "Disassembly" on page 29.
2. Disconnect the alert speaker.
3. Connect a known good alert speaker.
4. Place call to portable telephone from land-
line or other mobile/portable telephone and
verify alert signal volume and clarity. If
good, re-assemble portable with new alert
speaker.
5. If alert speaker not at fault, re-install original
alert speaker and proceed to c.
1. Replace Keypad/Display board.
2. If Keypad/Display board is not at fault, re-
install original Keypad/Display board and
proceed to d.
3. If Keypad/Display board is at fault, examine
it for improper solder and/or connections.
1. Replace Logic/RF Board Assembly.
2. If Logic/RF Board Assembly is at fault,
examine it for improper solder and/or
connections. Likely fail components: J2,
U703, and U900.
good Logic/RF
12/9/97