4.14 Change of Transmission HV setting: HV-9017
4-71
Transmission HV Protection Circuit
For instance, if the transmission high voltage 500 V for 25 kW type is used with 12 kW TR
unit, the protection circuit is activated to stop transmission.
High voltage is detected in TX high voltage input circuit on the MD board by dividing the
resistnace. The transmission high voltage detected in this way is compared with U22. If the
TX high voltage is higher than the specified value, TX triggers are stopped.
Fig. 4.14.2 Transmission HV Protection Circuit
Note:
1. TX pulse waveform differs depending on the setting of [Menu] -> 0 -> 4 -> 6:MODEL.
Though this is not related to the operation of protection circuit, be sure to check the
MODEL setting.
2. To check TX high voltage on the TR unit side, set [MENU] -> 0 -> 3-> 5:ANT SW to
OFF and stop antenna rotaion. Then, execute a check.
3. The detected TX high voltage is inputted to U19 (CPU) and this value is used for “HV”
indication on the self-test display. The self-test is executed by [Menu] -> 9 -> 8 -> 2 ->
2.
Tx-HV
MD p.c.b
(03P9244)
RFC p.c.b
(03P9346)
Mag.
TX-HV PROTCT
REF 2P5
-
+
TX-HV INHBIT N
U19
(CPU)
U17
(GATE ARRY)
TRIG 1-4
TRIG 1-4
TRIG 1-4
RF TXD/RXD
DATA/ADD.
U22
Compareter
To MD p.c.b
U4, 5
Q1-4
From RFC p.c.b
R1, 2
R40
R75
R76
R74
R77
R3, 4
Including HV
monitor signal
R40
X-band 12 kW TR unit: 39 kohm
X-band 25 kW TR unit: 18 kohm
S-band 30 kW TR unit: 18 kohm
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