Service BulletinAmateur Radio Division

Subject: TW-4100A - Repeater Stop Scan on the UHF BandDate: December 17, 1987

During repeater cross band operation, the TW-4100A may not detect a UHF signal while it is alternating between the two bands. This is due to the electric field generated by the strong UHF receiving signal causing the busy circuit to malfunction. The following modification will allow detection of the UHF signal.


  1. Remove the 4 screws securing the top cover.
  2. Remove the 10 screws securing the bottom cover.
  3. Carefully remove the top and bottom covers. Do not damage the speaker cable attached to the bottom cover.
    Refer to FIGURE 1 for the next 3 steps.
  4. Locate connector number 12 on the Composite unit (RX-TX) on the bottom of the transceiver.
  5. Carefully strip 1/8 inch of insulation from the wire attached to pin 2 connector 12 approxiamently 1/4 inch from the connector (do not break the wire).
  6. Solder the 3 components (listed above) between the wire and ground. A good ground location is the can around TC2 and L8.
  7. Assemble the transceiver by reversing steps 1 - 4.
Time required for this modification is 0.5 hrs or less.

©1987 Kenwood U.S.A