Troubleshooting By Symptom (Handset) - Panasonic KX-TG8421HGN Service Manual

KX-TG8421HGN/KX-TGA840FXN
9.3.

Troubleshooting by Symptom (Handset)

If your unit has below symptoms, follow the instructions in remedy column. Remedies depend on whether you have DECT tester
(*1) or not.
Note:
(*1) A general repair is possible even if you don't have the DECT tester because it is for confirming the levels, such as Acoustic
level in detail.
(*2) Refer to Check Point (Handset) (P.52)
9.3.1. Check Point (Handset)
Please follow the items below when BBIC or EEPROM is replaced.
Note:
After the measuring, suck up the solder of TP.
*: The Setting Method of JIG (Handset) (P.65) is required beforehand.
The connections of adjustment equipments are as shown in Adjustment Standard (Handset) (P.67).
Items
(A)* 1.8 V Supply Adjustment
(B)* BBIC Confirmation
(C)* EEP-ROM Confirmation
(D) Charge Control Check &
Charge Current Monitor
Check
(E)* Charge Detection (OFF)
Check
Check
Point
VDD1 1. Confirm that the voltage between test point VDD1 and GND is 1.8 V ± 0.02 V.
2. Execute the command "VDD", then check the current value.
3. Adjust the 1.8V voltage of VDD1 executing command "VDD XX"(XX is the
value).
- 1. BBIC Confirmation (Execute the command "getchk").
2. Confirm the returned checksum value.
Connection of checksum value and program number is shown below.
- 1. EEP-ROM Confirmation (Execute the command "sendchar EPV").
2. Confirm the returned Value (Value for reference is written at "EEPROM C/
SUM" in Software_Version_Table.xls).
- 1. Apply 3.5 V between CHG(+) and CHG(-) with DC power supply and set cur-
rent limit to 250 mA.
Confirm the indication of "charging" on LCD.
2. Confirm that the current limit LED of DC power supply is ON/OFF.
Confirm it after waiting over 1 minute at least.
3. Decrease current limit of DC power supply to 100 mA.
4. Confirm that the current limit LED of DC power supply is stable. (Current limiter
is ON.)
(If charge control cannot be confirmed by this procedure, please use battery to hand-
set power supply and try again.)
- 1. Stop supplying 3.5 V to CHG (+) and CHG (-).
2. Confirm the indication of "charging" has been cleared.
Procedure
52
Check or
Replace Parts
IC1, Q2, C48,
D1, C1, C44,
R12, R45,
C40, C45, F1
IC1, X1, RA61,
R64, R66
IC1, IC3,
R40~R42,
C172
IC1, Q4 Q9,
D7, R6, R7,
F1, C1, R2,
R30, R31, R8,
R45
IC1, Q4 Q9,
D7, R6, R7,
F1, C1, R2,
R30, R31, R8,
R45