Service BulletinAmateur Radio Division

Subject: TS-120S - Full CW Output in SSB ModeDate: December 18, 1980

Supercedes Service Bulleten of 7/13/80. See also SB-844 and SB-831.

Leakage or shorting of D2, D3 or D8 on the RF unit X44-1260-01 will provide an unwanted DC voltage path which gives full CW output while in SSB mode. The Carrier control has no effect, and RX is not affected.

Replace D2 1S2588, D3 1S1587, and D8 1S1585. Install two 1S1587 diodes between C4 and D8, as shown.

Radios before serial 080001 may not have D8. This may be added to the foil side of the board.

To install, swing the IF unit up. Remove the shield from under the IF unit to expose the foil side of the RF unit. Use a razor or X-ACTO knife to carefully cut the land between C4 and C20. Solder D8 across the cut, observing diode polarity. Some units have a 12pf cap soldered on the foil side of this board across T1, and C20 will be missing. Remove the 12pf and install a 33pf in C20's position. Solder the 1S1587's from the junction of C4 and D8 to ground.

Replacement Parts
Old Part No.
New Part No.
T1L34-0696-05/L34-0696-35L34-0929-15Antenna coil
C2015pfCC45RH1H330J (33pf)Capacitor

Changes are circled in green.

©1980 Kenwood