The level of residual noise (AF VOL at Min) on the SUB band is slightly higher than that of the MAIN band. This is especially true at audio frequencies of around 50 Hz, as viewed on a spectrum analyzer. As a result the SUB receiver is more susceptable to motor noise, such as might be generated by fans, refrigerators, etc.
Replacing the Control unit electrolytic capacitors (C33, C34, and C39) with Tantalum capacitors, and adding the bypass capacitor to the Switch unit reduces or eliminates this symptom.
Qty Description Kenwood Part No. Circuit Description
1 0.1 µF 35 V Tantalum capacitor C92-0001-05 C33
1 1.0 µF 16 V Tantalum capacitor C92-0004-05 C34
1 10 µF 16 V Tantalum capacitor C92-0505-05 C39
1 .01 µ disc capacitor CK45B1H103Z NA
Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance from your closest Kenwood Service Center (Long Beach, CA, or Virginia Beach, VA).
Time required for this modification is 60 minutes or less.