MODEL/
SECTION

SERVICE BULLETIN (SB)
AND/OR
SERVICE INFORMATION LETTER (SlL)

DESCRIPTION

KWM-1
TRANSCEIVER

SB lA
SB lB
SB 1C

SB 1D

SB IE

Improvement In Calibrator Operation.
Spurious Output Of KWM-1
Transient in Speaker When Switching
From Receive to Transmit
Hum In Speaker When AF Gain Control
Is Advanced in CW Operation
"Tweets" In Audio Output Caused By ..
DC Power Supply

KWM-2/2A
TRANSCEIVERS

SIL 1-75
SIL 2-75
SIL (2-3-60)
SB 1
SB 2
SB 3

SB 4

SB 5 (Revised)

SB 6


SB 7 (Reissue)

SB 8A


SB 8B

SB 8C

SB 9 (Revision 2)
SB 10

Overcome Instability Caused by Aging
Extended Operating Range
VFO Oscillator Drift
Not Issued
Add Vox Relay Time Constant Control
Correlation Between Frequencies On
Different Bands
Improvement of ALC Action And
Elimination of ALC Overshoot
To Improve Transmit-Receive Exciter
Tuning Coincidence
To Eliminate Delay In Operation When
Switching From Transmit To
Receive Function
Replacement of K2 and K4 With Plastic
Encased Plug-In Type Relays.
Eliminate AGC Overshoot On Noise
Pulses And Provide Dual Time
Constant Action
Change Source Of Delay Bias To
AGC Rectifier
Add Delayed-Decay (Hang) AGC To The
RF Amplifier
Convert KWM-2 To KWM-2A
Eliminate VHF Parasitic Oscillations
In Tone Oscillator, V2B

30L-1
LINEAR
AMPLIFIER

SB I (Revision)




SB 2
SB 3A

SB 3B

SB 4

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
Backward Deflection Of ALC Meter
To Lower Operating Temperature
Of PA Tubes
To Eliminate Pilot Light Fluctuation
With RF Excitation
Operation From 230 VAC Power Source

30S-1

LINEAR

AMPLIFIER

SIL (10-14-59)
SIL (2-15-60)

SB 1

SB 2

SB 3

Loading Of The 30S-1 Amplifier
What's Watt With SSB

To Increase Operating Life Of PA Tube

Prevent Intermittent Dropout Of Plate
Overload Relay
Reduce Excessive ALC Control

MODEL/
SECTION

SERVICE BULLETIN (SB)
AND/OR
SERVICE INFORMATION LETTER (SIL)

DESCRIPTION

32S-1/2
TRANSMITTERS

SIL (7-28-59)

SIL (2-3-60)
SlL 1-75
SB I
SB 2
SB 3
SB 4A
(Supercedes ~SB 4)

Use Of Transmitter As CW Exciter
for AM Mode.
VFO Oscillator Drift
Overcome Instability Caused By Aging
Improve VOX Operation
Improve Carrier Suppression
Add VOX Relay Time Constant Control .
To Improve CW Operation

32S-3/3A
TRANSMITTERS

SIL 2-75
SB I (Revision)


SB 2
SB 3
SB 4 Thru SB 6
SB 7 (Revision 2)

Extended Operating Range
Improve VOX Circuit To Eliminate
Intermittent Dropout, And Improve
Operation of First Audio Amplift,er
Removal of Audio Distortion
Not Issued
Replaced By SB1 Revision - - --'
Converts 32S-3 To 32S-3A

51S-1

RECEIVER

SIL 7-63

SB 1




SB 2 (Revision 2)

SB 3 (Revision)
SB 4
SB 5A
SB 5B
SB 6

SB 7

Reduced Hum In Audio Output With
Use Of 28-Volt D-C Power Supply
Suppression Of Unwanted Oscillations
In Low Level Audio Output Lines And
Allow Use Of Wiring Configuration
Shown In Figure 1-2 a. of The
Instruction Book
Replace Transformers T14 And T15
With Mechanical Filter
Improve Sensitivity of Lower Bands
Addition Of Dial Lock Assembly
Converts 51S-1A/1AF To 51S-1/1F
Converts 51S-1/1F To 51S-1A/1AF
Provision For High-Speed Receiver
Muting And Recovery
Reduce 500-kHz Spurious Response

55G-1
LF TUNER

SB I

Increase Current Handling Capacity of
115-volt Input Fuse.

62S-1
VHF
CONVERTER

SB I

Improvement In Operation of
ALC Circuit

75S-1/2

RECEIVERS

SII 2-75
SlL (2-3-60)

Extended Operating Range
VFO Oscillator Drift·

75S-3/3A

RECEIVERS

SIL 2-75
SB I
SB 2

Extended Operating Range
To Eliminate BFO Parasitic Oscillations
To Minimize Background Hum Level

75S-3B/3C
RECEIVERS

SIL 2-75
SB 1
SB 2
SB 3 (Revision 2)

Extended Operating Range
Improved Performance
Second Mixer Plate Circuit Improvement
Convert The 75S-3B To 75S-3C

MODEL/
SECTION

SERVICE BULLETIN (SB)
AND/OR
SERVICE INFORMATION LETTER (SlL)

DESCRIPTION

516E-1
12VDC
POWER
SUPPLY

SB I

Modification for Use with Positive
Ground

516E-2
28VDC
POWER
SUPPLY

SB *[

~

Add Bleeder Resistor to + 260 Vdc Line'to
Improve Safety Features of Power Supply.

516 F-2
AC POWER
SUPPLY

SIL 1-76

Prevent Fuse Blowing Caused By
Arcing In The Vacuum Tube
Rectifiers

PM-2

PORTABLE
POWER
SUPPLY
(KWM-2/2A)

SB 1 (Revision)

Extention of Design Specifications
for Input Voltage Limits

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