Kenwood KT-6040 FM Tuner Alignment



Optimum alignment of the Kenwood KT-6040 II can be accomplished with minimal equipment. A digital multimeter, hexagonal and planar blade plastic alignment tools, and a stable weak signal source will suffice. (Warning) attempts to align the hexagonal ferrite cores with a metal screwdriver will crack the ferrite!

Mark initial inductor/potentiometer positions with a black text marker. This will serve as a reference point.

RF Front-head Adjustment

First apply positive multimeter probe to TP11 and earth probe to TP12. If 3.0 volts (87.5 MHz) and 25.0 volts (108.0 MHz) are indicated on TP11, skip steps 1 and 2.

Step 1: tune to 87.50 MHz (DX RF mode and wide IF). Using a digital DC multimeter, adjust L12 for 3.0 volts on TP11.
Step 2: tune to 108.0 MHz (DX RF mode and wide IF). Using a digital DC multimeter, adjust TC1 for 25.0 volts on TP11. Repeat alignments 1 and 2 until no further improvement is obtained.

Sensitivity

Tune to 98.0 MHz (DX RF mode and narrow IF). Using a digital DC multimeter, adjust L1, L2, L4, L5, L10 for maximum DC volts on TP11 (maximum sensitivity). Repeat sensitivity alignments until no further improvement is obtained.

Tune to 98.0 MHz (DX RF mode and narrow IF). Using a digital DC multimeter, adjust L8 for maximum DC volts on TP11 (maximum sensitivity).

Auto-stop sensitivity (wide)

Tune to 98.0 MHz. With wide IF selected, adjust VR1 for desired auto-stop sensitivity.

Auto-stop sensitivity (normal)

Tune to 98.0 MHz. With normal IF selected, adjust VR2 for desired auto-stop sensitivity.

Auto-stop sensitivity (narrow)

Tune to 98.0 MHz. With narrow IF selected, adjust VR3 for desired auto-stop sensitivity.

IC IF amplifier stage adjustments

The following IF amp settings work best on my KT-6040. Keep in mind that these settings may or may not be appropriate for other KT-6040 tuners operating under different reception conditions.

Wide IF gain potentiometer (VR1) adjusted at roughly half way.
Normal IF gain potentiometer (VR2) adjusted for maximum gain, i.e., fully clockwise.
Narrow IF gain potentiometer (VR3) adjusted for maximum gain, i.e., fully clockwise.

Final points

A stable weak signal is needed on 98.0 MHz (+/- 200 KHz). The author used a home-built signal generator positioned in the backyard! It is important that the reference signal should be 100% received via an external (roof-mounted) antenna. If a stable reference signal isn't available, it may be possible to tweak the sensitivity using external atmospheric noise on ~ 98 MHz.

The above alignment procedures will provide optimum KT-6040 tuner DX performance. If necessary, other alignment procedures are included below.

Adjustment Procedures (1-13).

Adjustment Procedures (14-19).

KT-6040 component board.

T. Emslie 2006.