Collins Radio Service Bulletins and Information Letters
The CCA will continue to digitize and publish Collins Service Bulletins and Service Information Letters on this web site as they become available.
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- 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 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 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
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