32 Mhz Loop Fault Isolation Chart; Programmable Loop Fault Isolation Chart - Watkins-Johnson Company WJ-8718-19/FE Instruction Manual

MAINTENANCE
WJ-8718-19/FE HF RECEIVER
Disconnect the Frequency Counter and connect the RF
Volt meter and 50 ohm probe to W4P4. The Voltmeter
should indicate 0 dBm +/- 2 dBm,
If the signal in step 5 is incorrect, check the test
points given in Tables 4-22 through 4-24 with an RF
Voltmeter and oscilloscope. When a faulty signal is
encountered, replace the key components indicated and
repeat the Checkout Procedure. Figure 6-26, 2nd LO
Schematic Diagram should be referred to if additional
signal tracing/fault isolation is necessary.
When the 2nd LO has been repaired and is operating
satisfactorily, deenergize the receiver and disconnect
test equipment, if no further tests are to be performed.
Table 4-22. 32 MHz Loop Fault Isolation Chart.
Test Point
Normal Signal
Q5-B 2 Vpp
Ql-E
2 Vpp
Ul-1
1 MHz
Ul-3 1 MHz
U3-3
32 MHz
Ul-8 +3 Vdc
Key Components
Q5, CR3
Ql
Time Base
U2, U3
VCO circuits
Ul
Comments
VCO circuit
Reference Signal
Divide by 32
Phase Detector
Table 4-23. Programmable Loop Fault Isolation Chart.
Test Point
Normal Signal
Key Components
Comments
U16-15
3 Vpp @ 210 MHz Ql, CR5
VCO circuit
U14-11
3 V peak @ 2.09 MHz
U14, U15 Prescaler output
U12-3 3 V peak @ 10 kHz
U7-U11, U20
Counter output
U12-1 3 V peak @ 10 kHz
Time Base
U12-8
+6.2 Vdc
U12
Phase Detector
4-42