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. -------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- 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 ------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------------------------------------------------- Thats everything I hold up to 1989 that covers the SB-303. Enjoy! --------------------------------------------------------------------------------------------------------------------