Gremlins! It's Gremlins, I tell 'ya!

Discussion in '"Boat Anchor" & Classic Equipment' started by W6ELH, Sep 13, 2018.

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  1. W6ELH

    W6ELH Ham Member QRZ Page

    Have been enjoying myself wasting otherwise productive time working on a pair of Hallicrafters SX-28s this week. More correctly, one SX-28A and one AN/GRR-2. Parts arrived, so I bit my lip and started on the dreaded task of replacing the old wax-dipped paper condensers in the RF section.

    Took lots of photos, annotated them and gave each connection point a unique idenitifier as I unsoldered it. Finally, I had removed the third module working aft to forward. All of the paper caps were replaced, the resistors checked and replaced where warranted, and it was time to see if I could get it all back together. I had read there were 11 capacitors in this area, but my unit had only 10. Perhaps only the original SX-28 had 11? Yeah, that must be it.

    Lots of wrestling and fussing, but in due course, I had all the modules back in place and had made the final solder connection below the chassis. My chest swelled with pride as I surveyed my work. Yes, I could certainly be proud of, wait... WHAT? NOOOOOO!!!!!

    Now looking from another angle, I could see one more of the lil' devils buried way down in there. On the positive side, it was even more fun trying to pull a single module out while keeping the others in place, but in 45 minutes or so I had it on the bench. That little brown jasper was buried down behind the equally brown tube socket, and I simply didn't see him. Hmm, "Pride goeth before a fall." I think I read that somewhere!


    Finally all back together, I carefully powered up, and she's working! I can tell I need to perform an alignment, but it was operating well and broadcast AM surely sounded good through the PM23 speaker! So, take that, Gremlins! Cheers... Jim W6ELH

    KB4QAA, KC4UMO, KE0ZU and 1 other person like this.
  2. W7UUU

    W7UUU QRZ Lifetime Member #133 Volunteer Moderator Life Member Platinum Subscriber QRZ Page

    Very nicely done, Jim!

  3. KE0ZU

    KE0ZU Ham Member QRZ Page

    Congratulations Jim. Well done!!

    Mine still sits.
  4. WN2C

    WN2C Ham Member QRZ Page

    Good job Jim!
    I don't know what it is about that receiver but I always liked the look of it and have wanted one since I can't remember when. Maybe it's the lighted up dial faces and all those knobs.
  5. KC4UMO

    KC4UMO Ham Member QRZ Page

    Man you got to love it when they hide like that.
    Job well done.
    Thanks for sharing Jim.
  6. W6ELH

    W6ELH Ham Member QRZ Page

    Thanks fellows!

    Buddy - Is that storm bringing you lots of rain? You doing okay?

    Have been wrestling with the alignment process for the AN/GRR-2. IF alignment has been straight forward, but I'm not seeing the "double peaks" of the crystal filter as I'm supposed to. Have been using Bill Feldmann's (N6PY) procedure, so I think I'll try the manual method later today. Even when it throws up little roadblocks, doing this sort of thing is enjoyable for a duffer like me, and I seem to learn a little bit every time. That's where the fun is! And goodness, the SX-28 with the orangle glow of its meter and tuning dials is a handsome rig to look at! Cheers... Jim W6ELH
    KC4UMO likes this.
  7. KC4UMO

    KC4UMO Ham Member QRZ Page

    It got a little rough here but looks like we are ok now. The river was almost dry before the storm hit. Since the storm made a different path than foretasted will will only meet flood stage.

    How are you coupling to the IF stage? Perhaps it is dragging down the signals.
  8. W6ELH

    W6ELH Ham Member QRZ Page

    Good! Glad you are faring well.

    Sig-gen hooked to the C1.1 section of the main tuning capacitor per N6PY's instructions, and I'm keeping the output of the mixer tube down to -5 VDC per instructions. He has you first peak with the sig-gen at 455kc, then tweak the sig-gen frequency slightly to find peak output. This is supposed to be the crystal frequency. You peak the IF transformers again at this new (very slightly different) frequency.

    Where things get sticky for me, is you are now to "twiddle" the sig-gen frequency again to get a peak, followd by a significant dip and then a much smaller peak. I'm just not seeing that, nor does it stand to reason that if you previously peaked output by finding an "ideal" IF frequency, that you are going to get it to peak again. I'm sure I'm missing something.

    The factory manual method has you engage the BFO and listen for this in the speaker, and I also begin to wonder if you are supposed to massage the crystal phasing control ever so slightly to create this notch effect. I have some more experimentation ahead of me, but tofday was spent keeping the XYL happy, and that's seldom the wrong course of action! ;) Jim... W6ELH

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