P7689 / P7789 Repair Chart Table 2. GSM P7689 Cellular Telephone: Troubleshooting and Repair Chart. (Assembly Replacement Level). SYMPTOM PROBABLE CAUSE VERIFICATION AND REMEDY SYMPTOM PROBABLE CAUSE VERIFICATION AND REMEDY of 59 GSM Field Service Support 43 Personal telephone will not turn on or stay on a) Battery pack either discharged or defective Measure battery. If the battery voltage is b) Battery connectors open or misaligned. Visually inspect the 4 battery connectors on both the battery assembly and the portable telephone. If necessary, replace the battery. If battery is not at fault, proceed to c c) Logic/RF Board Assembly Defective. Remove the Logic/RF Assembly.
Substitute a known good assembly and temporarily reassemble the unit. 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 (see personality transfer). Verify that the fault has been cleared. If the fault has not been cleared then proceed to d. d) Display circuit failure Disassemble unit and remove LCD module and insert known good module. Insert Battery and depress PWR button. Ensure unit stays on, if OK reassemble unit in new housing assembly 2. Personal telephone exhibits poor reception and/or erratic operation (such as calls frequently dropping, Weak and/or distorted audio, etc.).
a) Antenna is defective Check to make sure that the antenna pin is properly connected into the Logic/ RF assembly. If OK, substitute a known good antenna and test in a call. If the fault is still present, proceed to b. b) Logic/RF Board Assembly Defective. Replace Logic/RF Assembly (refer to symptom 1c). Verify that the fault has been cleared and Re-assemble the unit with the new PCB. 3. Display is erratic, or provides Partial or no display. a) Mating connections to / from LCD Module faulty. Dissasemble unit, check display module is correctly seated on PCB display pads, if necessary refit or realign. If OK proceed to b. b) LCD module is Defective.
Substitute a known good LCD module onto the suspect board and connect to DC Pwr supply. Depress PWR and ensure display is now correct, if Ok rebuild unit with new LCD module if LCD module is not at fault proceed to c. c) Logic/RF Board Assembly Defective. Replace Logic / RF Assembly (refer to symptom 1c). Verify that the fault has been cleared and Re-assemble the unit with the new PCB. 4. Incoming call alert transducer audio distorted or volume is too low. a) Faulty alert Transducer Remove suspect alert transducer from rear housing and replace with known good alert. If fault does not clear proceed to b) b) Main RF / Logic PCB defective Replace Logic/RF Board Assembly (refer to symptom 1c).
Verify that the fault has been cleared