KB2LJJ Radio Mods Database
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1. 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 FT 757 Filtermodification During RTTY AMTOR operation it is useful 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 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 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 Connect the OFF contact to pin 5 of J10 SSB 8V and ON contact to pin 8 of J10 TX 8V Take another Diode of the same type and solder it s cathode to pin 1 of JO9 and the anode to ON contact of the second pole of toggle switch 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 have to cut the PCB between the contacts Further you have to remove all wires from the MOX switch That s all http www kb21 j com data yaesu ft 757 htm 3 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database Attention There are some errors in th2. K2KGH geckoraptar bigpond com My FT 757GXII did not have a switch so3 in that part of the board It had a 10 ohm resistor where the switch should be All I did was cut one end same as opening the switch and the mod worked ok 73 s Greg VK2KGH Yaesu FT 757GX and FT 757GX outputpower in SSB mode Author Uwe DJ9XG dj9xg O gmx net To use the Drive knob on the front panel in SSB mode install the following mod Remove the lower cover Put the radio upside down front side facing you Locate the front right hand corner of the RF Board Locate a coax cable TX In Locate 2 plastic transistors Q38 and Q39 Locate the resistor R 179 10Kohm black brown orange coloured Clip the longer leg of this resistor and bend it away Check if the drive function is working on SSB mode Install the bottom cover Have fun with this mod You can now change the output from zero watt to full output 100 watts very helpful in combination with a transverter or even a linear amp http www kb21 j com data yaesu ft 757 htm 8 di 9 07 09 2009 00 17 47 JJ Radio Mods Database 73 de Uwe DJ9XG
3. KB2LJJ Radio Mods Database www r6 ru4montesecchieta it IZSCCV YAESU FT 757GX amp FT 757GX Il EXPANDED RF Unplug the DC power cable from the radio Remove the top cover see service manual for cover removal Locate the Black slide switch on the display panel to the right of center and halfway down the backside Use a screwdriver to set the switch to the left most position Reassemble the radio Top case Black Switch Display Unit Modifications for the Yaesu FT 757 http www kb21 j com data yaesu ft 757 htm 1 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database FT 757 AM Filtermodification The orginal AM filter is too wide for shortwave listening 6 kHz There is a very simple way to decrease the bandwidth on AM mode to abt 3 5 kHz Just cut the wire bridge in front of JP 1020 left of CF01 looking from front side of transceiver on RF UNIT board Now take a new 1N914 or similar diode and solder it s anode to cathode of D61 and the cathode of this new diode to cathode of D58 or D59 Now the smaller SSB filter on 455 khz IF side is selected during AM The function of WIDTH system is also improved on AM now sideband selection is possible in AM with WIDTH knob SHIFT is out of function as before modification This modification does NOT work on FT757 Mod II because there is no second SSB filter You can find a CW filter modification for RTTY AMTOR in an other file I will send circuit diagrams of further
4. e Service Manual F e the filter connection is shown wrong If you want to have a corrected circuit diagram and complete modification diagram 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 The Display became dimmer more and more Hello FT 757GX users This bulletin intends only to provide help if you ever happen to have in your FT 757GX the same trouble I have just had THE TROUBLE While in receiving position the figures and symbols on display became dimmer more and more and then suddenly the display went off and reception stopped at once No transmission nor reception was possible Just the two pilot lights of the meter remained on THE SOLUTION The DISPLAY UNIT front panel has one transistor marked QO1 or Q4001 2SC496Y which is a NPN Silicon and its application is as oscillator for the DC to DC converter This transistor controls the TO1 DC to DC converter which among other things generates the 8 volts required in several sections of the circuitry the RF UNIT in particular is highly affected and the receiver does not work if this voltage is not supplied from the DISPLAY UNIT Removing the transistor in bad conditions and replaced by a cheap BD135 makes the rig feel happy and it worked right off the bat Special care is to be observed wh
5. ile removing the DISPLAY UNIT PC board There are three screws to be carefully removed to avoid washers falling into the jungle of wires and small parts There are some 12 press buttons in the front panel through which you apply pressure to their small switches on the PC board Two of them are a little bit difficult to remove the UP and DWN band channel buttons have squared holes where the shafts for these controls are placed before they reach the PC board Pulling gently and firmly the PC board backwards to the rear with the help of a screwdriver makes easier to free it Hope all this is of help to anyone needing to make repairs in this rig If you are not sure that you can make it for yourself ask your Elmer Best 73 s de Manuel EA7PSOEA7MU EACA ESP EU http www kb21 j com data yaesu ft 757 htm 4 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database FT 757GXII TX 1 5 to 30 MHz Disconnect FT757 from all connections Open tranceiver like explained in your Operating Manual Locate on the Display Unit SW03 and change is position Close tranceiver back and reconnect power This give you 100w between 1 5 and 30 mhz There is also a temporary solution without use of tools While the PTT key on the microphone is pressed push one of the up down keys at the frontpanel Now your 757GX transmit on the desired frequency but just for one transmission until you depress the PTT key I have had and still have 1 2 FT 757GXII tra
6. modifications on request Write to Roland Robic OE6RCD Augasse 15 A 8430 Leibnitz Austria Please enclose 3 IRC s in Europe or 5 IRC s outside Europe airmail to cover postage 73 s de Roland OE6RCD E OE3XBS AUTEU FT 757 Mod II Filter modification During RTTY AMTOR PACTOR operation it is useful to have an narrow filter to reduce QRM from other stations It is possible to use the narrow CW filter of the FT 757 II for SSB because of the filter shift system Cut the connection between cathode of diode D 101 and D102 on RF UNIT Take a new diode 1N914 or similar and solder it s cathode to the the cathode of D101 Connect the anode to middle contact of a double pole toggle switch http www kb21 j com data yaesu ft 757 htm 2 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database Connect the OFF contact to anode of D102 and ON contact to collector of Q56 TX 8V Take another diode of the same type and solder it s cathode to pin 1 of JO9 and the anode to ON contact of the second pole of toggle switch Connect the switching middle contact of second pole to collector of Q57 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 have to cut the PCB between the contacts Further you have to remove all wires from the MOX switch That s all If you want th have a complete modification diagram together with some other modifications write to
7. nceivers and both had the SW03 mod and both transmitted from 1 8 to 30 0 mHz I am currently using mine on the new 60 meter band Please note that this modification works well on the Aus import version of the Yaesu 757 GXII I was able to successfully transmit on 1 5 29 9999 Mhz straight into a dummy load However I am not sure if it is 100watts cw Isb right through the range Many thanks to ADA4S for his information and digital photos and to vk2kgh greg for his post Connect an PK232 to a FT 757 http www kb21 j com data yaesu ft 757 htm 5 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database Output CNX of PK232 The BRN wire and the shield of the PK232 cable are connected together You can use a alone cable for the reception of the PK232 wich is connected to the AF output of the FT757 instead of the RX audio green wire To avoid larsen you have to not have loop in your ground circuit So use only a alone ground link between the PK232 and the FT757 73 s of Ludovic Reset FT 757 GX and GXII Having Display trouble with your FT 757 GX Try RESETTING the Rig How to reset Press the LINEAR WIDTH POWER ON It should work vu2xxx You currently have Reset FT 757GX info However that only applies to the FT 757GXIL The correct procedure for the older FT 757GX is PRESS amp HOLD in LINEAR amp MARKER switches at rear of Radio Then Turn power on via front panel switch Restore Marker amp Linear Switche
8. s to the out position This has been tested amp works http www kb21jj com data yaesu ft 757 htm 6 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database Power MOD For Yaesu FT 757GX or GXII Author Haroldo Bradaschia Neto roggernet uol com br This adjust is to simple Put the radio with the VFO in front for you Turn the radio foots up and loose 4 screws the other side of transceiver Locate the 2 VR s VR1006 HF Bands MHZ Except 10 meters and VR1005 for 10 meters set the VR s Fully Clockwise and Have Aprox 160 watts All FM CW SSB operation and aprox 140 watts for 10 meters OBS the VR s can be a diferent names VR1006 VR 06 VR1005 VR 05 Haroldo Bradaschia Neto ZZ7 RDB Brazil A modificacao bem simples 1 coloque o radio com o VEO de frente para voce 2 Coloque o radio de cabe a para baixo e remova os 4 parafusos 3 Localize os 2 VR s VR1006 para todas as bandas exceto 10 metros e o VR1005 somente para 10 metros regule os VR s para o sentido horario todo aberto e voce ter aproximadamente 160 watts em todos os modos FM CW SSB e aproximadamente 140 Watts para 10 metros OBS O nome dos VR s podem ser diferente como no ex VR1006 VR 06 VR1005 VR 05 Haroldo Bradaschia Neto roggernetOuol com br ZZ7 RDB Recife Brazil http www kb21 j com data yaesu ft 757 htm 7 di 9 07 09 2009 00 17 47 KB2LJJ Radio Mods Database FT 757 sw mod for all band TX Author Greg V
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