Table of Contents
Advertisement
WJ-8718A/MFP
MAINTENANCE
7.
If a problem arises which affects all LEDs in either Group 1 or
Group 2 (refer to paragraphs 3.1.2.2.1 or 3.1.2.2.2), suspect the
common-cathode circuits.
a.
During operation, the inputs to
V4
(Group 1) and U8
(Group 2) should toggle.
Likewise, toggle outputs should
be evident at Group 1
(V4, V5,
and
V6)
and Group 2 (U8,
V9,
and
V10)
common-cathode <components. An input or
output stuck in the low or high mode is evidence of a
problem in the IC, or solder connections associat,ed with
the IC.
4.1.6
AUDIO SIGNAL TROUBLESHOOTING
Combined audio (A VDIO 1) from Audio Amplifier (A4A10), and ISB/LSB audio
(AUDIO 2) from ISB Detector/Audio Board A4A8 are routed through MFP Option switches and
amplifiers to the front panel phones jack. In addition, line audio voltage from Audio Amplifier
A4AIO passes through MFP switches to the front panel meter. The IF Interface (MFP-A3) and
the Front Panel Switch/Encode Assembly (MFP- AI) perform the functions provided by the
standard Front Panel Interconnect (A6A2) and the Front Panel Control (AIO).
Figure 4-3
illustrates the signal flow through the MFP Option in all detection modes except ISB.
Figure 4-4 illustrates signal flow in the ISB mode.
Section IV of the WJ-8718 Series HF Receiver Instruction Manual contains audio
troubleshooting charts, tables, and checkout procedures designed to localize audio problems.
These troubleshooting procedures can effectively localize problems to the MFP portion of the
signal path, if references to the standard Front Panel Interconnect and the Front Panel Conti'ol
are replaced by the equivalent MFP components, as shown in Figures 4-3 and 4-4.
4.1. 7
POWER SUPPLY TROUBLESHOOTING
The MFP Option utilizes the +15 and -15 Vdc supplies from the receiver rear panel
voltage regulators, and 10 V unregulated from the secondary windings of the power transformer
Tl.
Troubleshooting these power supplies is described in the WJ-8718 Series HF Receiver
Instruction Manual. Two additional supplies are associated with the MFP Option, described as
follows.
a.
Regulator MFP-A1A1
VI
is located in the front panel section.
A
voltage of 10 V unregulated enters the regulator via MFP-AIA2J1. A
voltage of approximately 7 Vdc should leave the regulator via
MFP-AIA2J2.
The output voltage is adjustable, as described in
paragraph 4.1.2.1.
b.
Voltage regulator MFP-
VI
is mounted on the back side of the front
panel. The regulator inputs 10 V unregulated and provides an output
of +5 Vdc to power the Front Panel Encode Board (MFP-AIA1). The
regulator is mounted in a location that is difficult to reach with test
equipment probes.
However, MFP-AIAI
VI
input +5 Vdc from
MFP-
VI
and is easily accessed. The IC is located at the top side of
the board and should have +5 Vdc on pin 4{).
4-27
Advertisement
Chapters
Table of Contents
