Collins Service Bulletin Index

Collins Service Bulletins and Service Information Letters
For the KWM-1/2/2A and S-Line Series of Amateur Equipment

SB  = Service Bulletin
SIL = Service Information Letter


KWM-1       SB 1A             Improvement In calibrator operation
            SB 1B             Spurious output of KWM-1
            SB 1C             Transient in speaker when switching from
                              receive to transmit
            SB 1D             Hum in speaker when AF gain control is
                              advanced in CW operation
            SB 1E             "Tweets" in audio output caused by DC
                               power supply

KWM-2/2A    SIL 1-75          Overcome instability caused by aging
            SIL 2-75          Extended operating range
            SIL 2-3-60        VFO oscillator drift
            SB 1              Not Issued
            SB 2              Add Vox relay time constant control
            SB 3              Correlation between frequencies on different
            SB 4              Improvement of ALC action and elimination of
                              ALC overshoot
            SB 5 Revised      To improve transmit-receive exciter tuning
            SB 6              To eliminate delay in operation when switching
                              from transmit to receive function
            SB 7 Reissue      Replacement of K2 and K4 with plastic encased
                              plug-in type relays
            SB 8A             Eliminate AGC overshoot on noise pulses and
                              provide dual time-constant action
            SB 8B             Change source of delay bias to AGC rectifier
            SB 8C             Add delayed-decay (hang) AGC to the RF amplifier
            SB 9 Revision 2   Convert KWM-2 To KWM-2A
            SB 10             Eliminate VHF parasitic oscillations in tone

30L-1       SB 1 Revision     Wiring change required before conversion from
                              115 To 230 volt operation is made, use of
                              8-ampere line fuses, and correction to
                              instruction book drawings
            SB 2              Backward deflection of ALC meter
            SB 3A             To lower operating temperature of PA tubes
            SB 3B             To eliminate pilot light fluctuation with
                              RF excitation
            SB 4              Operation from 230 VAC power source

30S-1       SIL 10-14-59      Loading of the 30S-1 amplifier
            SIL 2-15-60       "What's Watt With SSB"
            SB 1              To increase operating life of PA tube
            SB 2              Prevent intermittent dropout of plate
                              overload relay
            SB 3              Reduce excessive ALC control

32S-1/2     SIL 7-28-59       Use of transmitter as CW exciter for AM mode
            SIL 2-3-60        VFO oscillator drift
            SIL 1-75          Overcome instability caused by aging
            SB 1              Improve VOX operation
            SB 2              Improve carrier suppression
            SB 3              Add VOX relay time constant control
            SB 4A             To improve CW operation (Supersedes SB 4)

32S-3/3A    SIL 2-75          Extended operating range
            SB 1 Revision     Improve VOX circuit to eliminate intermittent
                              dropout, and improve operation of first
                              audio amplifier
            SB 2              Removal of audio distortion
            SB 3              Not Issued
            SB 4 Thru SB 6    Replaced by SB1 Revision
            SB 7 Revision 2   Converts 32S-3 To 32S-3A

51S-1       SIL 7-63          Reduced hum in audio output with use of
                              28-volt DC power supply
            SB 1              Suppression of unwanted oscillations In
                              low level audio output lines and allow
                              use of wiring configuration
            SB 2 Revision 2   Replace transformers T14 and T15 with
                              mechanical filter
            SB 3 Revision     Improve sensitivity of lower bands
            SB 4              Addition of dial lock assembly
            SB 5A             Converts 51S-1A/1AF to 51S-1/1F
            SB 5B             Converts 51S1/1F to 51S-1A/1AF
            SB 6              Provision for high-speed receiver muting
                              and recovery
            SB 7              Reduce 500-khz spurious response

55G 1       SB 1              Increase current handling capacity of
                              115-volt input fuse

62S-1       SB 1              Improvement in operation of ALC circuit

75S-1/2     SIL 2-75          Extended operating range
            SIL 2-3-60        VFO oscillator drift

75S-3/3A    SIL 2-75          Extended operating range
            SB 1              To eliminate BFO parasitic oscillations
            SB 2              To minimize background hum level

75S-3B/3C   SIL 2-75          Extended operating range
            SB 1              Improved performance
            SB 2              Second mixer plate circuit improvement
            SB 3 Revision 2   Convert the 75S-3B to 75S-3C

516E-1      SB 1              Modification for use with positive ground

516E-2      SB 1              Add bleeder resistor to +260 vdc line to
                              improve safety features of power supply

516 F-2     SIL 1-76          Prevent fuse blowing caused by arcing in
                              the vacuum tube rectifiers

PM-2        SB 1 Revision     Extension of design specifications for
                              input voltage limits

KWM-380                       (See separate listing on KWM-380 page)

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Most recent revision Wednesday, September 18, 1996