MODEL |
SB/SIL# |
DESCRIPTION |
SIZE |
KWM-1 |
SB 1A |
Improvement In calibrator operation |
990k |
Note** |
SB 1B |
Spurious output of KWM-1 |
990k |
" |
SB 1C |
Transient in speaker when switching from receive to transmit |
990k |
" |
SB 1D |
Hum in speaker when AF gain control is advanced in CW operation |
990k |
" |
SB 1E |
"Tweets" in audio output caused by DC power supply |
990k |
KWM-2/2A |
SIL 1-75 |
Overcome instability caused by aging |
103k |
| |
SIL 2-75 |
Extended operating range |
115k |
| |
SIL 2-3-60 |
VFO oscillator drift |
153k |
| |
SB 1 |
Not Issued |
|
| |
SB 2 |
Add Vox relay time constant control |
241k |
| |
SB 3 |
Correlation between frequencies on different bands |
209k |
| |
SB 4 |
Improvement of ALC action and elimination of ALC overshoot |
252k |
| |
SB 5 Revised |
To improve transmit-receive exciter tuning coincidence |
315k |
| |
SB 6 |
To eliminate delay in operation when switching from transmit to receive function |
139k |
| |
SB 7 Reissue |
Replacement of K2 and K4 with plastic encased plug-in type relays |
725k |
Note** |
SB 8A |
Eliminate AGC overshoot on noise pulses and provide dual time-constant action |
514k |
" |
SB 8B |
Change source of delay bias to AGC rectifier |
514k |
" |
SB 8C |
Add delayed-decay (hang) AGC to the RF amplifier |
514k |
| |
SB 9 Rev 2 |
Convert KWM-2 To KWM-2A |
642k |
| |
SB 10 |
Eliminate VHF parasitic oscillations in tone oscillator |
178k |
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 |
263k |
| |
SB 2 |
Backward deflection of ALC meter |
259k |
Note** |
SB 3A |
To lower operating temperature of PA tubes |
345k |
" |
SB 3B |
To eliminate pilot light fluctuation with RF excitation |
345k |
| |
SB 4 |
Operation from 230 VAC power source |
232k |
30S-1 |
SIL 10-14-59 |
Loading of the 30S-1 amplifier |
422k |
| |
SIL 2-15-60 |
"What's Watt With SSB" |
502k |
| |
SB 1 |
To increase operating life of PA tube |
388k |
| |
SB 2 |
Prevent intermittent dropout of plate overload relay |
149k |
| |
SB 3 |
Reduce excessive ALC control |
197k |
32S-1/2 |
SIL 7-28-59
|
Use of transmitter as CW exciter for AM mode |
244k |
| |
SIL 2-3-60 |
VFO oscillator drift |
153k |
| |
SIL 1-75
|
Overcome instability caused by aging |
103k |
| |
SB 1 |
Improve VOX operation |
336k |
| |
SB 2 |
Improve carrier suppression |
596k |
| |
SB 3 |
Add VOX relay time constant control |
382k |
| |
SB 4A |
To improve CW operation (Supersedes SB 4) |
337k |
32S-3/3A |
SIL 2-75 |
Extended operating range |
115k |
| |
SB 1 Revision |
Improve VOX circuit to eliminate intermittent dropout, and improve operation of first audio amplifier |
309k |
| |
SB 2 |
Removal of audio distortion |
134k |
| |
SB 3 |
Not Issued |
|
| |
SB 4 - SB 6 |
Replaced by SB1 Revision |
|
| |
SB 7 Rev 2 |
Converts 32S-3 To 32S-3A |
564k |
51S-1 |
SIL 7-63 |
Reduced hum in audio output with use of 28-volt DC power supply |
317k |
| |
SB 1 |
Suppression of unwanted oscillations In low level audio output lines and allow use of wiring
configuration |
116k |
| |
SB 2 Rev 2 |
Replace transformers T14 and T15 with mechanical filter |
515k |
| |
SB 3 Revision |
Improve sensitivity of lower bands |
138k |
| |
SB 4 |
Addition of dial lock assembly |
123k |
Note** |
SB 5A |
Converts 51S-1A/1AF to 51S-1/1F |
506k |
" |
SB 5B |
Converts 51S1/1F to 51S-1A/1AF |
506k |
| |
SB 6 |
Provision for high-speed receiver muting and recovery |
441k |
| |
SB 7 |
Reduce 500-khz spurious response |
351k |
55G 1 |
SB 1 |
Increase current handling capacity of 115-volt input fuse |
130k |
62S-1 |
SB 1 |
Improvement in operation of ALC circuit |
231k |
75S-1/2 |
SIL 2-75 |
Extended operating range |
115k |
| |
SIL 2-3-60 |
VFO oscillator drift |
153k |
75S-3/3A |
SIL 2-75 |
Extended operating range |
115k |
| |
SB 1 |
To eliminate BFO parasitic oscillations |
224k |
| |
SB 2 |
To minimize background hum level |
297k |
75S-3B/3C |
SIL 2-75 |
Extended operating range |
115k |
| |
SB 1 |
Improved performance |
1388k |
| |
SB 2 |
Second mixer plate circuit improvement |
968k |
| |
SB 3 Rev 2 |
Convert the 75S-3B to 75S-3C |
623k |
516E-1 |
SB 1 |
Modification for use with positive ground |
581k |
516E-2 |
SB 1 |
Add bleeder resistor to +260 vdc line to improve safety features of power supply |
200k |
516 F-2 |
SIL 1-76 |
Prevent fuse blowing caused by arcing in the vacuum tube rectifiers |
175k |
PM-2 |
SB 1 Revision |
Extension of design specifications for input voltage limits |
486k |
KWS-1 |
SB-1 |
Prevent off frequency oscillation appearing on output |
66k |
Note** |
SB-2A |
Use of crystal microphone with KWS-1 |
223k |
" |
SB-2B |
Prevent arcing of contacts on VOX relay |
223k |
" |
SB-2C |
Heat reducing tube shields |
223k |
Note** |
SB-3A |
Improved spark suppression of contacts of VOX relay K101 |
97k |
" |
SB-3B |
ALC modification |
97k |
| |
SB-4 |
Arcing of plate transformer T503 |
27k |
Note** |
SB-5A |
Type 4X250B tubes, variation in input capacity |
129k |
" |
SB-5B |
Change of F503 and F504 to slow-blow type |
129k |
Note** |
SB-6A |
Failure of L403 |
209k |
" |
SB-6B |
Improved filter chokes, L259 and L260 |
209k |
" |
SB-6C |
Modification to eliminate instability on 80 meters |
209k |
" |
SB-6D |
Modification to eliminate 100kc parasitic oscillation of P.A. |
209k |
" |
SB-6E |
Mod to eliminate parasitic oscillation in first mixer,V201 |
209k |
" |
SB-6F |
Replacement of carrier level control, R129 |
209k |
" |
SB-6G |
Synchronization of P.A. roller coils and tuning capacitor |
209k |
| |
A-Line SB's |
List of A-Line Service Bulletins that will be posted here |
196k |
75A-1 |
SB 2 |
Instructions for connecting a Panadapter |
255k |
" |
SB 3 |
Muting of 75A-1 receiver for CW break-in operation |
277k |
" |
SB 4 |
Operation of 75A-1 with break-in system |
295k |
75A-2A/3 |
SB 1 |
Mod to reduce noise in the receiver and improve s/n |
282k |
75A-3 |
SB 2 |
Suggested mods for serial# 1300 & above w/low-loss filters |
240k |
" |
SB 3B |
Mods for serial# 1299 & below w/high-loss F455B filters |
381k |
75A-4 |
SB 1 |
Improve noise limiter, revise Q multiplier, fuse blowing, etc. |
381k |
" |
SB 2 |
S-meter sensitivity pot replacement |
490k |
" |
SB 2A |
S-meter sensitivity pot and zero pot replacement |
305k |
" |
SB 3 |
Elimination of RF pickup while in standby position |
375k |
32V-2 |
SB 1 |
Simple filter modification |
402k |
32V-2 |
SB 2 |
Mods to eliminate the difficulty of low grid drive |
211k |
KWM-380 |
SB-1 |
Change mike impedance |
196k |
| |
SB-2 |
Improve transmit spectral purity |
167k |
| |
SB-3 |
Superseded by SB-16 |
111k |
| |
SB-4 |
Replace optical encoder |
83k |
| |
SB-5 |
Improve AF/RF pot tapers |
92k |
| |
SB-6 |
Correct transmit hum |
137k |
| |
SB-7 |
Reduce receiver birdies |
197k |
| |
SB-8 |
Improve receiver AGC action |
514k |
| |
SB-9 |
Stop PA oscillations |
405k |
| |
SB-10 |
Add WARC band transmit |
221k |
| |
SB-11 |
Add receiver low pass filter |
322k |
| |
SB-12 |
CW waveshape improvement |
219k |
| |
SB-13 |
Improve receiver AGC action |
169k |
| |
SB-14 |
Insure transmit audio response |
270k |
| |
SB-15 |
Add anti-static discharge path |
115k |
| |
SB-16 |
Improve frequency synthesis |
193k |
| |
SB-17 |
Add external tune line for CU-380 |
371k |
| |
SB-18 |
Eliminate RF pulse |
316k |
| |
SIL 1-81 |
Provide Mute Function For External Receiver |
134k |
| |
SIL 2-81 |
Connections to Collins S-Line Phone Patches |
166k |
| |
SIL 1-84 |
Product Improvement - To remove RFI susceptibility on the microphone input and speaker talk-back during
transmit. |
104k |
| |
SIL 2-84 |
Product Improvement - To substantially increase SSB talk power and improve VOX operation stability. |
103k |
| |
SIL 3-84 |
Product Improvement - To reduce spurious emissions from the power amplifier. |
159k |
| |
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. |
201k |
| |
|
|
|
| |
|
KWM/HF 380 Accessories Service Bulletins |
|
| |
AC-3803-SB-1 |
Control Interface - improve RFI filtering / coupling to CU-380 |
484k |
| |
AC-3801-SB-2 |
Noise Blanker - improve performance / add blanking |
889k |
