Modifications for the Yaesu FT-790
FT-790 Increasing the Power


You can readjust the ALC of the transmitter by adjusting VR3002.
Remove the top cover of the rig, then you will see the main unit, (which is called No. 30XX. in the circuit diagram). On the left you find a potentiometer named VR02. (In YAESU devices the component numbers are always composed of the Board number and the 'local' part number so, VR3002 is VR02 on board No. 30XX).
BE CAREFUL: I have not checked yet the specification of the output transistor. It is really possible that you should not raise the power above the specified 2.5 watts!!!
FT-790 Reducing the volume of the BEEP and sidetone


You can adjust this volume with VR4002.
Remove the bottom cover of the rig, then you will see board No. 40XX.
Look for VR02 (at the rear end of the board in the middle) and you've got it.

For each cover you only have to remove four screws. It is a little difficult to pull off the cover, but be patient.
9600 bauds mods for FT790r


Audio output from FT790R receiver's Discriminator for 9600bauds

Here is a very simple way of taking audio direct from the discriminator.

Connect a flying lead to pin 9 QO8 (MC3357P). (To save you having to burrow, just solder a lead on the IC pin itself). Drill a 1/4 hole in the case between standby and speaker sockets. Insert phono socket here and connect the flying lead and suitable Gnd. Thats it, job done.

TxAudio input into FT790R Varactor diode for 9600 bauds

Here are the details to input 9600 buads into the 790. Firstly make up the following circuit.
                470n
 Txaudio----->---] ]------------------22k----->To FC53M
            :           :       :
            :          22k     ---
            :           :      --- 10p
            :           :        :
 TxAgnd--->----------------------------------->Chassis Gnd
Notes:-

When you make up the above circuit, you must use very short leads!!!!

FC53M is a Varactor diode which is D1031 on the FT790r diagram.

FT-790R receiver's Discriminator for 9600bauds


Here is a very simple way of taking audio direct from the discriminator. Connect a flying lead to pin 9 QO8 (MC3357P). (To save you having to burrow, just solder a lead on the IC pin itself).
Drill a 1/4 hole in the case between standby and speaker sockets. Insert phono socket here and connect the flying lead and suitable Gnd.
Thats it, job done.

TxAudio input into FT790R Varactor diode for 9600 bauds

Here are the details to input 9600 buads into the 790. Firstly make up the following circuit.

                470n
 Txaudio----->---] ]------------------22k----->To FC53M
            :           :       :
            :          22k     ---
            :           :      --- 10p
            :           :        :
 TxAgnd--->----------------------------------->Chassis Gnd

Notes:-

When you make up the above circuit, you must use very short leads!!!!

FC53M is a Varactor diode which is D1031 on the FT790r diagram.


This counter shows the number of hits since the 9th February 2000


Go Back To The Yaesu Mods Page

Go Back To The Main Modifications Page

Go Back To The CB / HAM Radio Main Page

Go Back To The Main Home Page


Copyright © The Defpom 1997-2008

http://www.radiomods.co.nz/