Preselector Fault Isolation Chart - Watkins-Johnson Company WJ-8718-19/FE Instruction Manual

MAINTENANCE
WJ-8718-19/FE HF RECEIVER
Table 4-7. Preselector Fault Isolation Chart
Test Point
Normal Signal
Key Components
Comments
E5
+5 Vdc Dig. Control
Tune rcvr to 42 MHz
E3
+3 V
" ii Tune voltage
U3-3
0 Vdc
U3
CR10 anode 200 Mv
CR2
Tune gen to 42 MHz
CR15 anode 100 Mv
CR10-CR16
Check all diodes
ohmmeter.
wi th
El
100 mV
CR18
E4
+5 Dig. Control
Tune rcvr to 76.5 MHz
E3
+3 Vdc
it ii
Tune voltage
U3-5
0 Vdc
U3
CR3 anode
200 mV
CR1
Tune gen to 76.5 MHz
CR8 anode
100 mV
CR3-CR9
Check all diodes
ohmmeter.
with
El
100 Mv
CR17
"•
4'3-4-7 2nd LO Synthesizer, FE-A1A2A1, (794270) Testing and Troubleshooting
2nd LO Synthesizer Testing and Troubleshooting includes a checkout
procedure and fault isolation information. An oscilloscope, frequency counter and an
RF Voltmeter (see Table 4-1) are required to perform the tests outlined below
Perform the following procedure in the sequence given. If anv soecified
result is not obtained, refer to Table 4-8 for fault isolation. specitied
4-22
1.
2.
3.
Deenergize the receiver.
Connect the frequency counter to FE-A1A2-J5.
Energize the receiver. Set the receiver front panel
controls as follows:
a. Gain Mode- Manual
b. RF Gain - Maximum Clockwise
4. The frequency counter should indicate 189.0000 MHz.