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Yaesu FT- 757 mods
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FT757
de OE6RCD @ OE6UBG
FT 757 Filtermodification
During RTTY/AMTOR operation it is usefull to have an narrow filter
to reduce QRM from other stations. It is possible to use the narrow
CW filter of the FT 757 for SSB, because of the shift/width system.
1.) Cut the connection between cathode of diode D 102 and a 150 OHM
resistor on RF UNIT. This resistor is not shown in service manual,
but it exists on all rigs later LOT 4.
2.) Take a new diode (1N4148 or similar) and solder the cathode to the
open end of the 150 Ohm resistor. Connect the anode to middle
contact of a doubble pole toggle switch.
3.) Connect the OFF contact to pin 5 of J10 (SSB 8V) and ON contact
to pin 8 of J10 (TX 8V).
4.) Take another Diode of the same type and solder it's cathode to
pin 1 of J09 and the anode to ON contact of the second pole of
toggle switch.
5.) Connect the switching (or middle) contact of second pole to
pin 7 of J10 (RX 8V). The OFF contact will be let free.
For the SPDT switch I am using the MOX switch on the front panel.
It is a 2 pole toggle switch and you habe to cut the PCB between
the contacts. Further you have to remove all wirers to the MOX switch.
That's all.
Attention : There are some errors in the Service Manual. F.e the filter
connection is shown wrong. If you want to have a corrected circuit diagramm
or complete modification diagramm please write to Roland Robic OE6RCD,
Augasse 15, A-8430 Leibnitz, Austria.
Please enclose an A4 SASE ( 2 IRC or 4 IRC outside Europe Airmail)
This Modification should work also on FT757GX/II.
Best 73's de Roland OE6RCD @ OE6UBG or @ DK0MAV or you can write to
G3PLX AMTOR Mailbox.
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