Panasonic KX-TG7851UAB / KX-TG7851UAH / KX-TG7861UAB / KX-TGA785RUB / KX-TGA785RUH Service Manual ▷ View online
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KX-TG7851UAB/KX-TG7851UAH/KX-TG7861UAB/KX-TGA785RUB/KX-TGA785RUH
9 Troubleshooting Guide
9.1.
Troubleshooting Flowchart
Flow Chart
*1 KX-TG7861 only
Cross Reference:
Check Power (P.26)
Bell Reception (P.35)
Check Battery Charge (P.27)
Check Link (P.28)
Check the RF part (P.31)
Check Handset Transmission (P.34)
Check Handset Reception (P.34)
Signal Route (P.16)
Check Caller ID (P.34)
Check TAM Operation (for KX-TG7861 only) (P.35)
Bell Reception (P.35)
Check Battery Charge (P.27)
Check Link (P.28)
Check the RF part (P.31)
Check Handset Transmission (P.34)
Check Handset Reception (P.34)
Signal Route (P.16)
Check Caller ID (P.34)
Check TAM Operation (for KX-TG7861 only) (P.35)
Power ON Base Unit
Bell
Link
Battery Charge
Handset Voice Transmission
Handset Voice Reception
DTMF dial
OK
OK
No Link
OK
OK
OK
OK
OK
Not working
No bell
No voice
No charge
No voice
No signal
Check Handset Transmission
Check Handset Reception
Signal Route
Check Battery Charge
Bell Reception
Check Power
Check Link
Range
NG
Check the RF part
Caller ID Reception
OK
No signal
Check Caller ID
TAM Operation
*1
OK
Not working
Check TAM Operation
*1
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KX-TG7851UAB/KX-TG7851UAH/KX-TG7861UAB/KX-TGA785RUB/KX-TGA785RUH
9.1.1.
Check Power
9.1.1.1.
Base Unit
Is the AC Adaptor inserted into AC outlet? (*1)
Cross Reference:
Power Supply Circuit (P.12)
Note:
(*1) Refer to Specifications (P.7) for part number and supply voltage of AC Adaptor.
Is input of IC302 about 5.5 V?
Check C321, C341 are not shorted.
Check AC Adaptor.
Check Power Supply Circuit.
Is the output voltage of IC302 about 3V?
Does BBIC (IC501: XTAL1) oscillate at 10.368 MHz?
Check X501.
Check BBIC (IC501).
Is the Collector of Q301 about 1.8 V?
Is BBIC (IC501: RSTn) High?
Check BBIC (IC501).
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
Is the Collector of Q302 about 2.5 V?
YES
Is the output voltage of BBIC (IC501:CP_VOUT2)
about 3.0V?
about 3.0V?
Is the output voltage of BBIC (IC501:CP_VOUT1)
about 3.0V?
about 3.0V?
YES
YES
NO
NO
NO
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KX-TG7851UAB/KX-TG7851UAH/KX-TG7861UAB/KX-TGA785RUB/KX-TGA785RUH
9.1.1.2.
Handset
Cross Reference:
Power Supply Circuit/Reset Circuit (P.15)
9.1.2.
Check Battery Charge
9.1.2.1.
Base Unit
Cross Reference:
Charge Circuit (P.15)
9.1.2.2.
Handset
Cross Reference:
Check Power (P.26)
Charge Circuit (P.15)
Charge Circuit (P.15)
Check Power Supply Circuit/Reset Circuit .
Check BBIC (IC1).
Check F1 is not open.
Check X1.
Is the voltage of BATT+ 2.3 V more?
Check the battery and around BATT+ and
BATT- are not shorted.
BATT- are not shorted.
Is the battery inserted BATT+ and BATT-?
Does BBIC (IC1: 7) oscillate at 10.368 MHz?
YES
YES
YES
YES
NO
NO
YES
YES
Is the voltage of +1.8V about 1.8 V?
Is the voltage of CP3V about 3.0 V?
Check BBIC (IC1).
YES
Is the voltage of CP4.0 about 4.0 V?
(When LED is On)
(When LED is On)
YES
Is the voltage of CP2.8V about 2.8 V?
NO
NO
NO
Check Charge Circuit of Base Unit.
Check Handset.
Plug in the AC Power source.
Charge Handset on Base Unit.
Charge Handset on Base Unit.
Is the voltage of two charge contacts about
3 V or more?
3 V or more?
OK
NO
Check Charge Contacts at
Base Unit from mechanical point of view.
Base Unit from mechanical point of view.
YES
Is BBIC (IC1: 34) high at charge state?
Check Charge Circuit.
Check Power of Handset.
Is Check Power OK?
NO
NO
YES
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KX-TG7851UAB/KX-TG7851UAH/KX-TG7861UAB/KX-TGA785RUB/KX-TGA785RUH
9.1.3.
Check Link
9.1.3.1.
Base Unit
Note:
(*1) Refer to Troubleshooting by Symptom (Base Unit and Charger Unit) (P.36)
Cross Reference:
Check Point (Base Unit) (P.36)
Power Supply Circuit (P.12)
Power Supply Circuit (P.12)
Check around Power Supply Circuit.
Adjust +3.0V voltage to 3.0 V.
Refer to Check Point...(B).
Refer to Check Point...(B).
Does Base Unit make link with normal working
Handset?
Handset?
Check around X501 and adjust clock frequency.
Refer to Check Point...(G).
Refer to Check Point...(G).
NO
NO
NO (*1)
NO
YES
YES
YES
YES
YES
NO
NO
NO
Replace with a new Circuit Board.
Is the modulation OK?
Refer to Check Point...(K).
Refer to Check Point...(K).
Is the voltage of VBAT about 3.0 V?
Refer to Check Point...(A).
Refer to Check Point...(A).
Is there CMD60 (: DECT Tester)?
Does the RF clock (CLK) oscillate at 10.368 MHz in
Base Unit Test Mode?
Refer to Check Point...(G).
Base Unit Test Mode?
Refer to Check Point...(G).
Is the voltage of +3.0V about 3.0 V?
YES
Is the NTP value OK?
Refer to Check Point...(J).
Refer to Check Point...(J).
Does Base Unit make link with CMD60 in Base Unit
Test Mode?
Refer to Check Point...(J).
Test Mode?
Refer to Check Point...(J).
NO
YES
Base Unit is OK. Check Handset.
YES
YES
Is the Frequency Offset OK?
Refer to Check Point...(L).
Refer to Check Point...(L).
NO
OK
NO
NO
Is the Sensitivity Receiver OK?
Refer to Check Point...(M).
Refer to Check Point...(M).
YES
Is the Power RAMP OK?
Refer to Check Point...(N) .
Refer to Check Point...(N) .
Replace with a new Circuit Board.
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