TS-120 Modifications by WB4KDI

Proceed with these modification at you own risk. Your radio might be different!

Selectable Fast/Slow AGC

I have the 500Hz CW filter installed so I modified the J29(SSB/SSB) location to provide selectable fast/slow AGC. If you do not have the optional CW filter then the following instructions will have to be adapted for your installation.
  1. Remove D31 & D32.
  2. CUT trace from pin 2 J29(SSB/SSB) to pin 2 J29(SSB/CW).
  3. ADD wire from pin 1 of J28 to pin 1 of J29(SSB/SSB).
  4. ADD a SP/ST switch to the top panel near the VOX controls. There are several slots that can be used for mounting a small slide switch.
  5. Connect a pair of wires from J29(SSB/SSB) to the switch.
  6. With both pins of J29(SSB/SSB) connected together SLOW AGC is selected. When both pins are open, FAST AGC is selected.
DJB(WB4KDI) 5/83

Selectable High/Low Power

The Japanese have a power limit on 10 meters. In most rigs from Kenwood there is a low power circuit connected to the 10 meter logic line. In the TS-120S that signal is labelled B.
  1. Somewhere in the unit there should be a splice block connecting the B signal to the FILTER board. Locate the wire going to pin 6 of the FILTER board connector and cut that wire away from the splice block.
  2. Add a SP/DT switch to the top panel of the unit as above.
  3. Connect the wire going to pin 6 of the FILTER board connector to the center of the switch.
  4. Connect one side of the switch to 9v (can use pin 1 of J29(SSB/SSB) from mod above).
  5. Connect the other side of the switch to ground (speaker ground is OK).
  6. Set the switch to apply 9v and adjust VR2 for power output desired in low power mode. I adjusted mine to minimum power, 35 watts.
DJB(WB4KDI) 5/83

Selectable WIDE/NARROW Filters

A SP/DT switch can be added to the top panel of the unit to provide WIDE/NARROW filter selection independent of operating mode. For SSB operators who want the narrow SSB filter and RTTY (and Packet DJB/90) operators who want the CW filter in LSB connect each pin of J29(SSB/CW) to each side of the switch. Connect 9v (from AGC mod) to center of switch. Leave original J29 connector from mode switch disconnected.

DJB(WB4KDI) 5/83

Full Break-In CW

Here is one way to achieve full break-in CW with the TS- 120S:

Instead of connecting your key to the CW key input, connect your key to the PTT line. Then use the external relay contacts normally designed to key an external linear amplifier to key the CW key line. If your keyer has a weighting control you will want to set it somewhat heavier than normal to overcome the keying delays through the relay. I used this setup briefly and experienced no difficulties but got tied of hearing the relays clakety-clack.