Collins Service Bulletins and Service Information Letters

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Legend
  • SB : Service Bulletin
  • SIL : Service Information Letter
  • Multi : File contains multi-part Service Bulletins
MODEL SB/SIL# DESCRIPTION
KWM-1 SB 1A Improvement In calibrator operation
Multi 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
Multi 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 Rev 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
Multi 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 - SB 6 Replaced by SB1 Revision
  SB 7 Rev 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 Rev 2 Replace transformers T14 and T15 with mechanical filter
  SB 3 Revision Improve sensitivity of lower bands
  SB 4 Addition of dial lock assembly
Multi 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 Rev 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
KWS-1 SB-1 Prevent off frequency oscillation appearing on output
Multi SB-2A Use of crystal microphone with KWS-1
"     SB-2B Prevent arcing of contacts on VOX relay
"     SB-2C Heat reducing tube shields
Multi SB-3A Improved spark suppression of contacts of VOX relay K101
"     SB-3B ALC modification
  SB-4 Arcing of plate transformer T503
Multi SB-5A Type 4X250B tubes, variation in input capacity
"     SB-5B Change of F503 and F504 to slow-blow type
Multi SB-6A Failure of L403
"     SB-6B Improved filter chokes, L259 and L260
"     SB-6C Modification to eliminate instability on 80 meters
"     SB-6D Modification to eliminate 100kc parasitic oscillation of P.A.
"     SB-6E Mod to eliminate parasitic oscillation in first mixer,V201
"     SB-6F Replacement of carrier level control, R129
"     SB-6G Synchronization of P.A. roller coils and tuning capacitor
  A-Line SB's List of A-Line Service Bulletins that will be posted here
75A-1 SB 2 Instructions for connecting a Panadapter
" SB 3 Muting of 75A-1 receiver for CW break-in operation
" SB 4 Operation of 75A-1 with break-in system
75A-2A/3 SB 1 Mod to reduce noise in the receiver and improve s/n
75A-3 SB 2 Suggested mods for serial# 1300 & above w/low-loss filters
" SB 3B Mods for serial# 1299 & below w/high-loss F455B filters
75A-4 SB 1 Improve noise limiter, revise Q multiplier, fuse blowing, etc.
" SB 2 S-meter sensitivity pot replacement
" SB 2A S-meter sensitivity pot and zero pot replacement
" SB 3 Elimination of RF pickup while in standby position
32V-2 SB 1 Simple filter modification
32V-2 SB 2 Mods to eliminate the difficulty of low grid drive
KWM-380 SB-1 Change mike impedance
  SB-2 Improve transmit spectral purity
  SB-3 Superseded by SB-16
  SB-4 Replace optical encoder
  SB-5 Improve AF/RF pot tapers
  SB-6 Correct transmit hum
  SB-7 Reduce receiver birdies
  SB-8 Improve receiver AGC action
  SB-9 Stop PA oscillations
  SB-10 Add WARC band transmit
  SB-11 Add receiver low pass filter
  SB-12 CW waveshape improvement
  SB-13 Improve receiver AGC action
  SB-14 Insure transmit audio response
  SB-15 Add anti-static discharge path
  SB-16 Improve frequency synthesis
  SB-17 Add external tune line for CU-380
  SB-18 Eliminate RF pulse
  SIL 1-81 Provide Mute Function For External Receiver
  SIL 2-81 Connections to Collins S-Line Phone Patches
  SIL 1-84 Product Improvement - To remove RFI susceptibility on the microphone input and speaker talk-back during transmit.
  SIL 2-84 Product Improvement - To substantially increase SSB talk power and improve VOX operation stability.
  SIL 3-84 Product Improvement - To reduce spurious emissions from the power amplifier.
  SIL 1-88 Product Improvement - To prevent receiver front end filter select diodes A3CR800 thru CR807 from being damaged or blown by T/R relay A2AK1 switching transients or large voltage spikes produced at the receive input.
     
    KWM/HF 380 Accessories Service Bulletins
  AC-3803-SB-1 Control Interface - improve RFI filtering / coupling to CU-380
  AC-3801-SB-2 Noise Blanker - improve performance / add blanking