Drv Board: Pa Transistor (Q4-Q5) Bias Adjustment (Fs-2575, -5075) - Furuno FS-1575 Service Manual

TP4-5: PA BIAS
CHECK (BIAS=4mV)
R79: PA BIAS ADJ.

1. DRV Board: PA transistor (Q4-Q5) BIAS adjustment (FS-2575, -5075)

Procedure-1) Making measurement with ammeter
1. Turn OFF the power supply, and then connect a 1A/DC ammeter to the 24V line
between #1 and #3 of J6 of the PA Vcc connector.
DRV
(05P0866A, B)
Fig. 5.7.12 DRV Board: Q4-Q5 BIAS Measurement Circuit
2. Disconnect the [J1: TX OUT] connector from the TX board.
3. Turn ON the power supply, and then press the PTT on the handset to put the system
into a TX state.
CONFIDENTIAL (internal use only)
This confidential document is used only by FURUNO authorized persons.
It is strictly prohibited to reproduce the document in whole or in part without prior written permission of FURUNO.
Q4, Q5
Fig. 5.7.11 DRV Board (05P0866A, B)
-
Ampere
Meter
[J6]
#1-3: 24V
#4-6: 0V
5-41
Q1
Q2, Q3
TP2-3: DRV BIAS
CHECK (BIAS=100mV)
+
[J1]
#1-3: 24V
P-SW
(05P0871)
#4-6: 0V
5.7 Board Adjustment
R77: Q1
PRE-DRIV BIAS ADJ.
R78: Q2-Q3
DRIV BIAS ADJ.
TP2-1:
PRE-DRIV
BIAS CHECK
(BIAS=75mV)