Icom IC-751A Service Manual page 136

SECTION 11 OPTIONS INSTALLATION
11-1 OPTIONAL FILTERS
© FILTER REVERSE SWITCHES
The [FILTER] SWITCH on the front panel of the IC-751A
selects two receive filter systems for SSB, CW, RTTY or AM
mode when it is switched to either the IN or OUT position.
The IN/OUT relationship of the [FILTER] SWITCH may be
reversed by using the internal FILTER REVERSE
SWITCHES on the MAIN UNIT.
S3: Reverses the IN and OUT positions of the [FILTER]
SWITCH when using AM mode.
S4: Reverses the IN and OUT positions of the [FILTER]
SWITCH when using CW or RTTY mode.
NORMAL ) NORMAL
$3 $4
REVERSE REVERSE
(1) FL-52A, FL-53A FILTER INSTALLATION
These are 455kt filters for use with CW NARROW or RTTY
NARROW mode.
No special tools are required to successfully complete the
installation of these filters. Install them at position [F] in the
photo on p.11-5.
1) First, remove the top cover.
2) Insert the optional FL-52A or FL-53A into position [F] as
shown in the photo on p.11-5.
3) Check the operation of the filter using the FILTER
COMBINATIONS TABLE for a guide (p.11-5).
(2) FL-63A FILTER INSTALLATION
This is a 9MHz narrow filter for CW or RTTY mode. The filter
replaces the standard FL-32A which is supplied with the
IC-751A. Install this filter at [A] position as shown on p.11-5.
1) Remove the transceiver top cover, then the 11 screws
from the MAIN UNIT.
2) Lift the right edge of the MAIN UNIT upwards taking care
not to damage the sockets and plugs that are installed on
the unit.
3) The filter must be installed at position [A] in the photo as
shown on p.11-5.
Remove the FL-32A original filter from the MAIN UNIT
using a de-soldering braid.
4) Install the FL-63A at position [A]. Orient the label on the
filter in the same manner as the other filters already
installed.
5) Bend the leads and mounting tabs flush against the
opposite side of the printed circuit board, and solder.
Trim the ends of the leads with diagonal cutters.
6) Replace the MAIN UNIT and screws, and the top cover.
There are no adjustments required after installation is
completed.
(3) FL-70 FILTER INSTALLATION
$3 $4 Ic3
° o———_© W97
o——o — — —0 wo8
o- — —@e—— W99
The FL-70 is a 9MHz wide filter for SSB mode which may be
installed for either of the following two reasons:
a) To replace the standard FL-80.
b) To replace the standard FL-32A.
a: Use the FL-63A installation method given previously.
Place the FL-70 in the position where the FL-80 is now
installed.
b: 1) Use the FL-63A installation method given previously.
Place the FL-70 in the position where the FL-32A is
now installed.
2) The FL-70 operates only in CW or RTTY mode if it is
installed in the FL-32A location.
Therefore, perform the following modification so the
FL-70 may or may not be used as desired.
3) W98 and W99 jumper wires on the MAIN UNIT must be
changed as shown in the diagram above.
4) The FL-70 and Fl14 (CFJ-455K5) can now be selected
by pushing the [FILTER] SWITCH on the front panel
IN. The receive bandwidth will be 2.8kHz.
11—1