ASB-1036 (APU-0017)
Service BulletinAmateur Radio Division

Subject: TS-450S - Driver Transistor Parts ChangeDate: December 8, 1993

The 2SC2509 driver transistors are no longer available. They have been discontinued by the manufacturer. A substitute transistor (2SC3133) is available but requires some minor circuit changes These changes are detailed below.

Parts Required:

Kenwood Part No.
Circuit Description
2Driver Transistor2SC3133Q2, Q3
2330 1W Carbon resistorsRC05GF2H331JR8, R9
1.047 uF Ceramic capacitorC91-0119-05C2
2220 pF Ceramic capacitorCC45SL2H221JC64,C65
1560 pF Ceramic capacitorCC45SL2H561JC63


Make the following changes on the HF Final Unit (X45-3400-XX)
  1. Change C2 to 0.047 uF. This is connected to the base of Q1
  2. Change C63 to 560 pF. This is conneced to the Emitter of Q1
  3. Change R8 and R9 to 330 0hm. These are connected to the collectors of Q2,Q3
  4. Add 220 pF caps (C64,C65) from the collector to emitter of Q4 and Q5
  5. After install of the new driver transistors (2SC3133) readjust the bias current according to the instructions contained in the service manual.
C64 and C65 should be soldered directly to the collector and emitter pins of the final Transistors Q4 and Q5.

Time required for this modification is 60 minutes or less.

©120893 by CLM for Kenwood U.S.A. (E51-93-041)