| 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
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
T9 Specs |
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 |
