Panasonic KX-G8300 Service Manual And Technical Manual page 67

KX-G8300 .
Troubleshooting step 11:| No change in echo or noise even when GAIN cotrol is adjusted.
Possible Causes
rs) Improper connection of GAIN control, VR155 on preset board
fe) IF amplifier failure
Checks
1) Check the voltage at rear panel connector pin 2 on the display unit. It should change to approx. 8
to 9.5 Vde when the GAIN control is turned. If there is no change, check the connections at the
GAIN control and of VR155 on the preset board.
2) Check the voltage at connector CN602 pin 6 of the IF amplifier. If there is the same change as in
1), the IF amplifier may have failed.
Troubleshooting step 12:| No alarm tone.
Causes
oO Failure of alarm amplifier circuit (Q11) on processor board
oO Failure of alarm amplifier circuit (Q4, Q22, Q24) on processor board
0) Failure of alarm circuit (IC29) on processor board
0 Improper connection of VR151 on preset board
fe) improper connection of external speaker
Checks
(Set the alarm zone and proceed in the alarm mode.)
1) If the built-in alarm is problem-free and no sound is heard through the external speaker (option),
check the external speaker connections.
2) Use an oscilloscope to check the signal of wire W1 #6 on the processor board. It should be pos
sible to observe a pulse train (approx. 2 kHz, 5Vp-p). If this signal is not present, the processor
board has failed.
3) If the signal in 2) is problem-free, check the wire W1 #7 signal. If a pulse train (approx. 2 kHz,
2Vp-p) is not observed even when VR151 on the preset board is turned clockwise, check the
VR151 connections on the preset board.
4) Check that the signal in 3) is problem-free and check the signal at connector CN7 pin 1 for the
external speaker. If a pulse train (2 kHz, 5Vp-p) is not observed, the amplifier circuit (Q4, Q22,
24) on the processor board has failed.
5) Use the oscilloscope to observe the signal of IC29 pin ?? on the processor board. A pulse train
(5Vp-p, 2 kHz) should appear. If not, the processor board has failed.
6) Use an oscilloscope to observe the signal of cable W2 #2 for connecting the buzzer element. A
signal (approx. 3Vp-p, 2 kHz) should be observed. If the signal is present, the element has failed;
If itis not present, Q11 on the processor board has failed.
Troubleshooting step 13:) No change in key backlight brightness or no lighting.
Possible causes
Open filament in lamps PL201-206
Control panel Q201 failure
Processor board TR85 failure
Processor board 1C27 failure
Key switch failure
oooo0o°o
Checks
1 When the backlight does not come on, connect the emitter of Q201 on the control board to GND.
An open filament in a lamp is to blame if the lamps do not light.
2) Monitor pin 3 of connector CN6 on the processor board. A pulse train (approx. 100 Hz, 5Vp-p)
should be observed while the PNL DIM key is kept pressed. If it is not observed, the control board
has failed.