tttTS790(e) MODS


My idea was to disable the 1750Hz feature on the TS790E and enable the sub tone encoder.

Kenwood USA was not willing to help (because I'm outside the usa) and Kenwood Belgium says it can not be done.

Before You even open the tranceiver try to work ESD (anti static) safe, use a wristband connected to a 'clean' earth make sure Your soldering iron is connected to the same 'clean' earth.


After looking at the diode chart of the control unit I saw that one diode is only used in the E (European) version, so I thought it would be easy to convert it, the biggest trouble was to find the D21 diode I was on the back of the control unit, after removing the diode it was possible to switch sub tones on and off BUT there was no way I could set the freq of the sub tones (the micro processor still saw the TS790 as an E version).

So there is no way to get that working properly unless You change it to the K version (I don't know if the J, M, M2, W2, W3 have the sub tone feature).

In the Netherlands You may have a tranceiver that works outside the ham bands so converting is no problem.

here is what I found out that some of the diodes do (if someone has more info I would like to know it)

D21 - 1750Hz when present / enable sub tones when not present

D29 - Wide RX if not present

D30 - Wide TX if not present

D32 - Cross band repeater if not present

Well to change the European version to the K version you have to cut the following diodes (do it so that it is possible to reconnect them, You never know if you want to return it to it's original state)

Cut D21, You have to remove the entire control unit because its on the back of the control unit (be careful with the flat cables and remove the iron clip that is holding the left ic on its place) (I cut the copper line on the cathode side of d21)

Cut D30,29,24,23,21 (I have cut them about 5 mm away from the glass)

Now place a 1N4148 into the D22 place (You do not have to stick it all thru just make sure it makes good contact) it has the same polarity as the other (previously cut) diodes

If You want wide RX cut D29 

If You want wide TX cut D30

Well putt everything back together, the only thing I had to change are the freq steps (to 12.5KHz) and the repeater shift (0.6 and 1.6KHz)

Now I can work repeaters with a sub tone Like Rotterdam and Antwerp.


I like to thank PA3HGT and PA3DSC for giving me the schematics (because my service manual was held up in the mail)


Well all the pictures should make things very easy for You, If there are any problems or suggestions pse e-mail me: