Modifications for the Yaesu FT-757

Picture(s) of Yaesu - FT-757

19-07-1998 FT-757 AM Filtermodification English language (1 Kbytes)
19-07-1998 FT-757 Mod II Filtermodification English language (1 Kbytes)
19-07-1998 FT-757 Filtermodification English language
19-07-1998 The Display became dimmer more and more English language (2 Kbytes)
19-07-1998 FT-757GXII - TX 1,5 to 30 MHz English language (1 Kbytes)
20-02-1999 Connect an PK232 to a FT-757 English language (1 Kbytes)
14-03-2001 Reset FT-757 GX and GXII English language (1 Kbytes)
 View all modification in one click. This can be a very big file.!! (9 Kbytes)

19-07-1998
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 (1N914 or similar) and solder the cathode to the open end of the 150 Ohm resistor. Connect the anode to middle contact of a double 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 (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 wires from 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 and complete modification diagramm together with some other modifications, write to Roland Robic OE6RCD, Augasse 15, A-8430 Leibnitz, Austria.

Please enclose 3 IRC (Europe) or 5 IRC (outside Europe Airmail) for covering postage.

Best 73's de Roland OE6RCD @ OE3XBS.AUT.EU

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