Return to the Virtual Collins Radio Museum
SB = Service Bulletin
SIL = Service Information Letter
MODEL SB/SIL# DESCRIPTION
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
bands
SB 4 Improvement of ALC action and elimination of
ALC overshoot
SB 5 Revised To improve transmit-receive exciter tuning
coincidence
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
oscillator
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)
Return to the Virtual Collins Radio Museum
Copyright © 1996-WA3KEY & Collins Radio Company
This Home Page was created by wa3key, Wednesday, September 18, 1996
Most recent revision Wednesday, September 18, 1996