============================================================================== 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 ============================================================================== BULLETIN # 1060 MODEL: TM-733A SUBJECT: PL Tone Distortion Symptom: Transmitted PL Tones at the receiving station have a relatively high level of distortion. This is easily seen when the incoming signal is viewed on an oscilloscope. Countermeasure: Change the value of the "Pull-up" resistors in the PL tone encoder circuit as shown in the accompanying chart. This reduces the distortion from around 9% to approximately 4%. Parts Required: Qty Description Old Kenwood Part No. New Kenwoood Part No. 1 R542 (from 1.8K to 2.7K) RK73FB2A182J RK73FB2A272J 1 R543 (from 1.8K to 3.3K) RK73FB2A182J RK73FB2A332J 1 R544 (from 1.8K to 4.7K) RK73FB2A182J RK73FB2A472J 1 R545 (from 1.8K to 6.8K) RK73FB2A182J RK73FB2A682J 1 R546 (from 1.8K to 1OK) RK73FB2A182J RK73FB2A103J 1 R547 (from 1.8K to 1OK) RK73FB2A182J RK73FB2A103J 1 R548 (from 1.8K to 1OK) RK73FB2A182J RK73FB2A103J Procedure: 1. Disconnect the power cable, microphone and antenna's, etc. 2. Detach the front panel and set it aside. 3. Remove the top and bottom covers. 4. Remove the speaker and speaker mounting bracket 5. Disengage the plastic front panel from the main chassis. 6. Carefully disconnect the two ribbon cables from the TX/RX unit C/4. 7. Remove the two Phillips head screws that secure the TX/RX unit to the chassis. 8. Turn the circuit board over and replace the resistors using the parts list above. 9. Reverse steps 1-7 for reassembly. These components are located on the foil side of TX-RX Unit (X57-4360-00) near IC402. Caution: This modification requires advanced surface mount soldering equipment that is rated for CMOS circuits. It also requires familiarity with advanced 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. Service code A:06 B:X57-4360 C:R542 D:91