Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 198

WJ-8718-19/FE HF RECEIVER
MAINTENANCE
9. When the BFO has been repaired and is operating
satisfactorily, deenergize the receiver and disconnect
test equipment, if no further tests are to be performed.
Table 4-26. BFO Fault Isolation Chart.
BFO OFFSET = 0
Test Point
Normal Signal
Key Components
Comments
U9-8
Ql-C
U10-1
Ul-13
U2-13
U3-13
U4-13
U9-3
U9-1
+3 Vdc
2 Vpp @ 4.55 MHz
3 V peak @ 4.55 MHz
3 V peak @ 455 kHz
3 V peak @ 46 kHz
3 V peak @ 5 kHz
3 V peak @ 1 kHz
3 V peak @ 1 kHz
3 V peak @ 1 kHz
U9
Ql, CR1
Q2, Q3
Ul
U2
U3
U4
U5-1 U9
Time Base
Phase Detector
VCO Circuit
4.3.4.24 Time Base, p/o A5A1. (p/o 791630) Testing and Troubleshooting
Time Base Testing and Troubleshooting includes a checkout procedure and
fault isolation information. AFrequency Counter and a wideband Oscilloscope (Table
4-1) are required to perform the tests outlined below.
Perform the following procedure in the sequence given. If any specified
result is not obtained, refer to Table 4-27 for Fault Isolation.
1.
2.
3.
4.
Deenergize the receiver.
Connect the Frequency Counter input to A5XA1 pin A9
using a sh.ort coaxial cable with clip leads on one end.
Connect cable shield to Motherboard ground plane.
Energize the receiver. The Frequency Counter should
read 1.000000 MHz +/- 3 Hz.
Move the Frequency Counter clip lead to A5XA1 pin
A47. The Frequency Counter should read 10.000 kHz
+/- 1 Hz.
4-45