Panasonic KX-G8300 Service Manual And Technical Manual page 64

KX-G8300
Troubleshooting Step 6:| Noise appears but no echoes.
Possible Causes
ooooo0o°o
Processor Board failure
Thyristor D802 failure
Magnetron failure or it has reached the end of its service life
Thyristor trigger circuit Q801, Q802 circuit failure
Pulse transformer T801 failure
MIC failure
Checks and Repairs
1)
2)
3)
4)
Set the radar to the transmit mode, and use a multimeter to monitor the voltage at the
magnetron current monitor point on the preset board in the display unit and at pin 2 of connector
CN803 on the modulator board.
Monitor voltage
If the voltage is between 1.5 and 2.5 VDC (at 3NM range) the problem may lie with MIC which
should be replaced.
Heater voltage: 5.7 to 6.9 VDC
| | | | 8V
a4 L- Approx. 10 psec
Fig. 65
If the trigger pulse is generated by the processor board, check the modulator board as
follows.
i) Confirm that the D803 anode voltage is approx. 300VDC in standly (transmit OFF)
condition.
ii) Set the unit to transmit mode, and confirm the trigger pulse at below points.
1
Approx. 10 V
Q802 Emitter 7] L
|
|
Approx. 3 psec
I
s
!
CN802-Pin =a es = ae —5V
OV
Fig. 66