Collins Radio Service Bulletins and Information Letters

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  • SB : Service Bulletin
  • SIL : Service Information Letter
  • Multi : File contains multi-part Service Bulletins
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 KWM-2 Component List KWM-2 Component List
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

32S3 SB1 Final

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