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                             K E N W O O D
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                        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

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BULLETIN # 844
MODEL: TS-120S
SUBJECT: TX OSCILLATION (SUPERCEDES 821)
                                                        
      The TS-120S may exhibit intermittent oscillation on the 15M,
      10M, and/or 20M bands. Symptoms may be no control of Carrier
      level, full current or ALC in either CW or SSB after initial
      keying or modulation, or "full output both forward and reflected".
     
      1. Physically disconnect power form the radio.
      
      2. Make certain the Antenna fitting is tight to the rear panel.
      
      3. Remove covers. Unplug speaker lead.
      
      4. Check for loose screws securing the RF unit X44-1260-01
         and the relay unit X41-1250-00 (located over the RF unit).
          
      5. On the RF unit, check diodes D2,3 and 8 for high reverse
         leakage. If in doubt, replace.
          
      6. I not already present on the RF unit, make the following
          chanqes:
          
         R47 (33 OHMS change to 10 OHMS Radial (RD12CY2ElOOJ)
         R50 (560 OHMS) change to 680 OHMS Radial (RD12CY2E681J)
         C61 (22OPF) Remove
         
         Add 2 lS1587 (V11-0370-05) diodes in series, anode to
         ground from the junction of C4 and D8.
         
     NOTE: Diode I.D. lS1587 = lS1585 
           Added diodes may induce RX IMD. If so delete.
             
      7. As illustrated, carefully cut the cable ties on the wire
          harness (without cutting the wires) as it rounds the corner
          behind the PLL unit X50-1490-00.
          
      8. Seperate the AVB line, a white/brown line from the filter
         unit X51-1200-00 to the RF unit X44-1260-01
          
      9. Adjacent to the rear of the PLL and to the left you will
         see a five pin terminal strip. The two right-hand most
         terminals are bridged. WITHOUT BREAKING THE TERMINAL OR
         STRIP, remove the heavy yellow, and light red and green
         lines and transfer them to the adjacent terminal. There
         will now be seven lines, plus the positive end of Cl
         on the second terminal. Be sure to cut the wire jumper
         between these two terminals.
          
     10. The free terminal will be a tie point for the AVB line
         bypass capacitor. Solder a .01pF 50V disc ceramic
         (C52-1710-36) between ground and the first free terminal.
         Use spaghetti to insulate the leads. Then solder the
         AVB line to the .01pF cap.
    
     11. Retie the cable harness with nylon cable ties (J61-0401-05).

     12. Replace the covers and speaker lead. Power-up and verify
         correct operation.
    
NOTE: Installation time for this procedure is approximately 1/2 hour.