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34263Re: [Heathkit:Yahoo] How long does it normally take to realign a 401/303 pair?

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  • w5rkl
    Jul 2, 2014
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      Perform the SB-303 +15VDC adjustment FIRST before you do anything else!!! This adjustment determines the other voltages that are used in the receiver. This adjustment is covered in the SB-303 assembly manual.

      Follow the alignment steps as stated in the SB-401 assembly manual, don't jump around or try to side step an adjustment.

      Make sure the tubes are good as alignment counts on the tubes being good, not gassy or weak.

      When performing carrier null in the SB-401, you will have to adjust the carrier null POT and VARIABLE CAP for a carrier null "compromise" between USB and LSB. Do NOT adjust for full carrier null on one sideband as the other sideband will have carrier. If the CAR NULL POT is intermittent, typical for this pot, then replace it with a multi turn vertical adjust 200 ohm pot. The CAR NULL POT has a tendency to fail over time. Cleaning only results in short lived results. I use a separate receiver tuned to the SB-401 transmit frequency. It doesn't matter what band you do the carrier null on because the CAR NULL adjustment is at the Carrier Generator's "Balance Modulator" which is the same sideband (USB and LSB) output frequency regardless of the band selected!!

      Pay close attention when adjusting the SB-401 Het Osc coils, making sure you adjust for a peak from the "slow rise" side of the adjustment NOT the "fast rise" side. If you don't pay attention then you will adjust using the wrong side, it's easy to do trust me, I've done it before!! If, after you adjust the SB-401 HET OSC coils, you have full output in ALL MODES on ALL BANDS with the MIC/CW Level control set fully CCW, then you did the HET OSC coil adjustment wrong, redo the HET OSC coil adjustments.

      Mike W5RKL
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