Watkins-Johnson Company WJ-8718A/MFP Instruction Supplement page 125

TABLE 4-6
6.
7.
WJ-8718A/MFP
If an IC in a particular location repeatedly requires replacement, the
conditions external to the IC should be checked: resistors, Vcc,
ground connections, solder joints, and connections to unused sections
of the ICs.
The information in paragraph 4.1.3.2, Symptoms of Integrated Circuit
Failure, can be referenced to aid in locating defective ICs.
4.1.4.2
IF Interface Modules (MFP-A3)
There are four IF Interface modules to support the microprocessor system.
Troubleshooting is indicated when a failure occurs in an area of operation within the functional
boundaries of one of the modules. Primarily, these modules serve to store data associated with
the IF bandwidth, gain mode, detection mode and AID conversion for monitoring receiver
operations. The data is utilized by the signal processing circuits in the receiver, and is used for
switching the RF gain voltage and audios. If the receiver is equipped for optional remote
operation, board functions include analog-to-digital conversion of signal strength voltage and
digital-to-analog conversion of remote RF GAIN voltage. The board also contains modules
which when used with a standard front panel, interface the microprocessor with front panel
components through J2, J3, and J4. In this application, front panel interface is accomplished
through the Front Panel Encode Board (MFP-A1A1). The front panel interface modules and
output jacks are unused.
Tables 4-6 and 4-7 list all information pertinent to the modular structure. The
tables are to be used in conjunction with the information in paragraph 4.1.4.2.1.
Table 4-6. IF Interface Modules
Data Module
1
2
3
4
Description
D/A:
RF gain Programmable IF register (1) IF register (2)
AID
Functional Circuit U23 U25 U5
U9
Tri-State Buffer NA
Internal (U25) Internal (U5)
Internal (09)
Buffer Clock NA NA
NA NA
Address Capture Latch U8 NA U8
U8
Address Capture Clock U10B, pin 6 U19C, pin 8 U10B, pin 6
U10B, pin 6
Address Decode U11, pin 12 Internal (U25) U11, pin 14 U11, pin 13
NOTE: NA denotes not applicable.
4-14