                        November 25, 1970
SB-303                                          Bulletin No:
Ham Receiver                                    SB-303-1

                     SB-303 Operation With SB-610 Monitor Scope

Envelope monitoring with the SB-610 is satisfactory with the SB-303.
Using the 1.0 uF coupling capacitor provided, approximately 1/4"
peak-to-peak deflection is obtained with an S-9 signal.  Connection is
made to the collector of Q503, 3rd IF Amp. on the IF/Audio board.
Retuning of [PN 52-125], T-503, is not required.  However, should more
deflection be required, a larger capacitor could be used and would
probably require a slight retuning of T-503.
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                        November 25, 1970
SB-303                                          Bulletin No:
Ham Receiver                                    SB-303-2

                        SB-303 Operation With SB-620

Scanning operation of the SB-620 is satisfactory with the SB-303
receiver.  Connection is made to the drain of the 2nd Mixer, Q204 on the
Mixer board with the 7.5 pF capacitor provided.  Retuning of L-202 does
not appear necessary unless AGC is removed and a signal generator used
for alignment.  AGC does have, of course, an effect on the SB-620 display
amplitude.
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                        December 28, 1970
SB-303                                          Bulletin No:
Ham Receiver                                    SB-303-3

                                       FET

Since performance can vary a great deal with the variation in tolerances
of the 40673 FET, a permanent change is being made.

Change:  [PN 417-240] 40673 FET to [PN 417-274] RCA 40673 FET.

Note:  PN 417-217 Specifies RCA as the vendor and also calls for tighter
specifications.
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                        August 14, 1973
SB-303                                          Bulletin No:
Ham Receiver                                    SB-303-4

                Intermittant Connections Of The IF-Audio
                        And BFO-Power Supply Boards

Installing spacers [PN 255-1] between the chassis and connector mounting
plates reduces spacing between board connectors & chassis connectors.
This assures a much tighter connection and allows a better orientation of
switch wafers to shafts, etc.

The #6-1/4" smet screws are to be replaced with #6-3/8" smet screws - 12
required.

Threaded press-in standoff spacers will appear in production when parts
are available.
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                        January 11, 1974
SB-303                                          Bulletin No:
Ham Receiver                                    SB-303-5

                              Instability

Oscillations [audio] can be cured by tinning the edges of IF and BFO
circuit boards to improve grounding.
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                        May 23, 1974
SB-303                                          Bulletin No:
Ham Receiver                                    SB-303-6

                      Signal Input Checks For SB-303 Receiver

Equipment Needed- - -

        VTVM
        RF Signal Generator with 3db pad
        Audio Generator

Set Controls To Positions Indicated---

        Function - Operate
        Converter - H.F.
        Preselector - 10 o'clock
        R.F. Atten - Fully CW
        Band - 3.5
        Main Tuning - 0.00
        AGC - Fast
        R.F. Gain - Fully CW & pushed in
        Mode - USB
        A.F. Gain - 12 o'clock

Connect VTVM and set to 5 volt A.C. range across 8 ohm speaker.  Set
audio generator for 1 Khz and connect to points indicated.

        INPUT POINT     INPUT LEVEL     VTVM READING
        Base of Q509           .25 Volts                 2 volts
        Base of Q507                   .2   Volts                2 volts

                                  (P=E[SQD]/R )   P=4/8  = 1/2 watt

REMOVE AUDIO GENERATOR AND CONNECT RF SIGNAL GENERATOR AT POINTS
INDICATED.
Use a .005 MFD capacitor for isolation.

FREQUENCY       INPUT POINT     INPUT LEVEL     S METER READING
3395 Khz                Base of Q503    25000
Microvolts              S-9
3395 Khz                Base of Q502      3000
Microvolts              S-9
3395 Khz                G1 of Q501        1000
Microvolts              S-9
8895 Khz                G1 of Q204          700
Microvolts              S-9
3500 Khz                G1 of Q203          300
Microvolts              S-9
3500 Khz                G1 of Q101            30
Microvolts              S-9
3500 Khz                **Antenna             15
Microvolts              S-9

Check RF voltage at points indicated [RF probe needed]

BFO out    -     .45 volts
HFO out    -   1.5   volts
Q203 G2  -      .6   volts
Q204 G2  -      .3   volts

**Remove .005 MFD Capacitor
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                        January 6, 1975
SB-303                                          Bulletin No:
Solid State Ham Receiver                                SB-303-7

                               Parts Obsolescence

PN 417-105 will be replaced by PN 417-133 in this kit.
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                        October 22, 1975
SB-303                                          Bulletin No:
Solid State Ham Receiver                                SB-303-8

                     Circuit Breaker Screw Strips Out

Before replacing the circuit breaker because the threads have been
stripped, try using a slightly larger screw, [PN 253-55] to secure the
breaker.
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                        March 4, 1976
SB-303                                          Bulletin No:
Solid State Ham Receiver                                SB-303-9

                   Crystal Oscillator Fails To Start

This problem can be corrected by installing the following change:

Change:  Q102 from [PN 417-133] to [PN 417-172].

The replacement 417-172 transistor is a 3-lead plastic-case device,
whereas the 417-133 is a 4-lead Metal case transistor so be sure the
transistor leads are installed in the correct holes.
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Thats everything I hold up to 1989 that covers the SB-303.  Enjoy!
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