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

MAINTENANCE
6.
7.
9.
WJ-8718-19/FE HF RECEIVER
Set the receiver front panel controls as follows:
a. Gain Mode-
b. RF Gain -
Manual
Maximum Clockwise
Connect the RF Voltmeter to connector A3A2J2 using a
short coaxial cable (a "TEE" connector should be used
to maintain 50 ohm termination).
Connect the Signal Generator to connector A3A1J1 using
a short coaxial cable. Set the Generator output
frequency to 15.00500 MHz and output level to -7 dBm.
Energize the receiver and tune to 15.00500 MHz.
The RF Voltmeter should display a level of 350 mV.
IF the signal in step is incorrect, check the Test
Points given in Table 4-11 with an RF Voltmeter and
high impedance probe. When a faulty signal is
encountered, replace the key components indicated and
repeat the Checkout Procedure. Figure 6-13, Input
Converter Schematic Diagram should be referred to if
additional signal tracing/fault isolation is necessary.
When the Input Converter has been repaired and is
operating satisfactorily, deenergize the receiver and
disconnect test equipment, if no further tests are to be
performed.
Table 4-11. Input Converter Fault Isolation Chart
Test Point
Normal
Signal
Key Components
Comments
A1J2
1.8 V
at 57.91 MHz
Check 1st LO
1st LO Signal
Ul-8
74 mV
at
42.905 MHz
Ul
1st IF
FL1-IN
200 mV
at
42.905 MHz
U2
FL1-OUT
80 mV
at
42.905 MHz
FL1
A2Q2-S
40 mV
at
42.905 MHz Input Matching Network
A2Q2-D
500 mV
at 42.905 MHz
A2Q2, TI, C16, CR2
A2J1
260 mV
at
32.205 MHz
Check 2nd LO
2nd LO Signal
A2Q6-B
500 mV
at 32.205 MHz
A2Q5
A2Q6-C
1.3 V
at 32.205 MHz
A2Q6
A201-3
130 mV
at 10.7 MHz
A2U1
2nd IF
A2Q3-C
1.3 V
at 10.7 MHz
Q3, Q4, T2
A252
350 mV
at
10.7 MHz
FL1
L
4-28