Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 203

MAINTENANCE
WJ-8718-19/FE HF RECEIVER
4.3.4.26
IF Interface, A6A2, (796032) Testing and Troubleshooting
IF Interface Testing and Troubleshooting includes a checkout procedure
and fault isolation information. A Digital Voltmeter and a wideband Oscilloscope
(Table 4-1) are required to perform the tests outlined below.
The testing and troubleshooting information in this paragraph is keyed to
several fault isolation tables. These tables are used to isolate the module fault to a
defective integrated circuit or functional group of integrated circuits. Perform the
following procedure in the sequence given. When a faulty signal is encountered,
replace the key components indicated in the table.
1. Deenergize the receiver.
2. Remove the receiver top cover.
3. Place module A6A2 on an extender card.
4. Set the receiver to the following parameters:
~
a. Tuned Frequency
b. Bandwidth
c. Gain Mode
d. Detection Mode
e. Tuning Rate
15.00500 MHz
50 kHz
AGC FAST
AM
10 Hz
Using the oscilloscope, verify control signal/data
activity indicated in the following table.
Table 4-32
. IF Interface Control Signal/Data Activity
Check
Test Point
Normal Signal
Key Components
Comments
XU1 Pins 12-19 Pulse train,
U9,U14
Addr/Data Bus
l e s s than
794275 PCB
1 us prr.
U13 Q0-Q2,
Square wave,
U13,u4
Address Latch
Q4,Q5
1 msec PW.
U7 Y0-Y6
Pulse train,
less than
1 msec PW.
U4,U21,U13
Address Decoder
U17-10
+ 5 Vdc
U19,U17 RF Gain Voltage
RF Gain Control
a t max cw.
4-50