Re: TS-440 Low Power Adjustment/ Kenwood Svc Bulletins


From: Bill Howell (
Date: Fri Nov 22 1996 - 16:20:31 EST

Steve- This is the Service Bulletin location.
Download Indexmod.txt to see which bulletins apply to your Kenwood rig.
There are several for the '440.

There is another location which has APPLICATION NOTES. This is info on
various models which may not have been covered in the owners manual.

Here's the one you are probably interested in:

                             K E N W O O D
>>> A M A T E U R R A D I O S E R V I C E B U L L E T I N <<<

                        Kenwood Service Centers

   Kenwood Service Corporation Kenwood Service Center, East
   2201 East Dominguez Street 829 Lynnhaven Parkway, Suite 130
   Long Beach, California 90801 Virginia Beach, Virginia 23452
   Telephone 1-310-639-5300 Telephone 1-804-340-1702



The VCO and active low pass filter are sealed in synthetic rubber to
mechanically stabilize them during mobile operation. Over a period of
several years, the rubber's insulation properties can break down. This
may be caused by repeated temperature variations. This can cause the VCO
to vary in frequency which will force the loop to unlock or cause the
audio to warble.

This modification will correct or prevent an unlock caused by VCO #5.



1. Disconnect the power supply and antenna.

2. Remove the top and bottom covers. Do not damage the speaker wires
   when removing the top cover.

3. Remove the two screws from the rear of the IF unit and raise the unit
   to expose the PLL board.

4. Remove the 8 screws from the PLL board and disconnect all the cables
   going to the board.

5. Remove the board from the transceiver.

6. Remove the shield cover from VCO #5. Desolder and remove the shield
   from the PLL board.

7. Carefully remove the synthetic rubber from the area of Q34, Q35, and D14.
   The rubber must be picked off the board with pointed tweezers or some
   other tool. It cannot be removed with any type of solvent as this will
   harm the components in the area. You can heat the rubber with a hot
   air gun to allow it to be picked off a little easier, but be careful
   not to overheat the components in the area.

8. Desolder and remove Q34, Q35, and D14 from the PLL board.

9. Check the component side of the board to make sure all the rubber in
   the area of Q34, Q35, and D14 is removed.

10. Once the rubber is removed, replace Q34, Q35, and D14 with new components.

11. Inspect and resolder the foil side of the PLL board under VCO #5.

12. Install the VCO shield on the PLL board and solder it in place.

13. Seal the VCO with hot melt glue (glue stick used in a hot melt glue
    gun). Apply the glue to the circuit from the glue gun. Once the area
   is covered, use the hot air gun to flow the glue around the components.
   Do not overheat the components.

14. Install the PLL board in the transceiver.

15. Apply power to the transceiver and allow it to run in receive for
    about a half hour so the transceiver's temperature stabilizes.

16. Set the operating frequency to 14.200MHz.

17. Adjust T20 to obtain 5VDC at TP11 (the exposed lead of L40) measured
    with a DVM or VTVM. Do not use a VOM. After adjusting the VCO, bench
    run the transceiver for an hour or more to make sure the circuit
    is stable.

18. Assemble the transceiver.

Time required to perform this modification is 1 hour or less.

Bill Howell
University of Texas at Austin
Performing Arts Center
Electronic Maintenance
voice: (512) 471-1388
N5ALO QRP-L #415

everything is sacred
nothing is serious

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