National Company NC-300 Full alignment & Demo as 6AL6 replaced with diodes and .56 cap on AVC line

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  • Опубліковано 25 чер 2024
  • Found out I had messed up the First IF 2115 alignment of the Q-Multipler.
    and this degraded total receiver performance.
    Here the 80 KHz IF was aligned again (see a few videos before this one) One IF can
    was a bit off on the 80 Khz IF strip.
    Of major concern was the proper alignment of the multiplier and the first IF at 2215 Khz.
    First in the instructions one will look for peak S meter reading around 2212 to 2218 Khz and the
    signal generator is swept across the frequencies for best S meter reading.
    I think I got 2067.720 Khz which means the crystal has drifted LOW by 148 Khz
    After you find the resonant frequency of the crystal you adjust L6 for a peak. L6 is very sensitive so turn it very little.
    After L6 is adjusted for max we move the signal generator UP 2 Khz.
    Position 1 on Select and then L4 for a max S-meter reading.
    Now remove the 2 Khz increment from the signal generator by decrementing 2 Khz.
    We are now at the original PASS frequency of the crystal filter
    Select switch OFF
    and adjust C16 for max output. This is DIFFICULT due to the rotary frequency display cylinder in the way.
    And now get max S-meter from peaking T4 and L2A.
    I always get this far OK.
    The former "mess up" is here:
    There is a step where the signal generator is moved from the center crystal pass or resonance
    frequency by the ADDITION OF 160 Khz to the 2067.720 crystal resonant pass frequency on the signal generator and then a coil on the multiplier deck side on top is tuned for a DIP. So I looked for a dip at 2227.720 Khz by adjusting coil L2B.
    !!! Last time I did this I moved the generator UP only 16 Khz or UP even 1.6 Khz. Mistake !!!
    So add 160 Khz to the pass frequency of the crystal.
    Select switch OFF
    Increase the generator output for an S-5 reading..
    Now L2B for min reading.
    And return the signal generator to the crystal pass frequency by subtracting 160 Khz
    Now max S reading of L2A.
    And again:
    repeat
    So add 160 Khz to the pass frequency of the crystal.
    Select switch OFF
    Increase the generator output for an S-5 reading..
    Now L2B for min reading.
    And return the signal generator to the crystal pass frequency by subtracting 160 Khz
    Now max S reading of L2A.
    AND DONE!!!!
    At any rate the proper alignment got the receive sensitivity way way up.
    Even on 11 and 10 meters.
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