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Set screws breaking when trying to recalibrate

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  • Set screws breaking when trying to recalibrate

    So, I recapped the AV generator and measured its outputs. Most seems well, but there are a couple of frequencies that are way off, and I realise that if I tweak some 20 pickups I'll have close to an ideal curve.

    So I start out by fixing the one frequency that was really out there, 4 times louder than its neighbors and fluttering. All is well, but as I tighten its screw it snaps off! Horror, but at least I got to set it at its proper level.

    So I proceed, and the next one snaps trying to _undo_ it, before even adjusting. So I guess I'll recalibrate that one by experimenting with capacitance in its filter instead.

    But, how to get those pesky screws loose without breaking even more? Penetrating oil? Other tips, anyone?
    Current organs: AV, M-3, A-100
    Current Leslies: 22H, 122, 770

  • #2
    Something that might be worth a try is Supco "rust buster", a penetrating oil product. This stuff has worked for me freeing stuck setscrews, pulleys, fan blades and blower wheels from motor shafts, etc. in hvac equipment. Might at least improve the odds. Comes in a "tele-spout" bottle.
    Tom in Tulsa

    Fooling with: 1969 E100, 1955 M3, 1963 M100, Leslie 720


    • #3
      I'll assume that you have the correct spline wrench... not trying use the "closest size" Allen Hex wrench.
      A drop of PB BLASTER should loosen them up, but it comes in a spray can, so maybe shake it up, spray some into a glass jar and go from there.
      It's awesome stuff, Magnus... even for freeing up rusty "frozen" pistons in barn-find engines.
      C-3 with O-M, 145, 122RV, 2 PR-40's, PSR-36
      CV with HR-40, 2 B-40's


      • #4
        Penetrating oil for sure. There are many good products on the market, and I am sure that any of them will do the job. All else is not available, WD40 will do.
        I use a dropper or syringe and put a bit on the screw as well as the pickup rod because more often than not there is some corrosion between that collar and the rod. If you have an areosol, spray some in a cup or dish before using the is just a little less messy as the spray gets everywhere.
        Apply and let it soak in before attempting to loosen the screw.

        When dealing with fasteners this small, finesse is the rule of the day. If you feel the slightest resistance turning in any direction, do not force, but turn the screw opposite way and apply more oil.

        When unscrewing, you need to "feel" your way.
        To begin, "bump" the screw with a little force in both directions until you feel the screw break free.
        Notice that the screw may feel loose for small part of a revolution then get tight again.
        Unscrew until you feel resistance, then go just a slight bit more, then turn the other way until it feels snug again, then unscrew till you feel resistance and apply a little pressure, then keep going back and forth until the screw turns freely.
        What you are doing here is breaking down the corrosion that is in the threads and preventing it from jamming the threads and siezing the screw in place.

        You are dealing with a very small screw that only requires a few inch-ounces of torque to do it's job.
        When you go to tighten the screw, you only need to apply a little pressure to the wrench after the screw makes contact.

        I use a 5/32 combination wrench, available many places for a couple $. The wrench that you see on many Hammond parts sites for this purpose is too large IMO, and make it too easy to break or strip those small screws.
        Click image for larger version

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        In theory, there is no difference between theory and reality.
        In reality, there is.
        '54 C-2 & Pair of 122 Leslies
        H-324/Series 10 TC
        '35 Model A (Serial# 41) with a 21H
        Look at some of my rescues:


        • #5
          Great instructions, as usual, Bob. I was thinking scanner set screws when I entered my hasty response. I should NEVER reply to anything here until after my second kuppa kawphy ! Nevertheless, the PB Blaster is great stuff for loosening stuck things. Forgive my confusion guys.:embarrassed:
          Roger Memphis
          C-3 with O-M, 145, 122RV, 2 PR-40's, PSR-36
          CV with HR-40, 2 B-40's


          • #6
            We use a flexible shaft 1/4" driver with the appropriate socket - very hard to over-do it. If/when that doesn't work, I have a crescent wrench that's about 2" long.


            • #7
              After my M3 pickup replacement episode, and having to adjust 17 magnets , I've opted for the capacitance matching method for the BCV filters.
              The anti-seize compounds are similar like Bob said,PB Blaster brushed on warm carefully and left overnight unstuck all but one.
              I gave the magnet post a second of butane heat so when it cooled bingo!
              Those little butane torches really are handy around stuck sheet metal.Gave it a bump with a rubber mallet.
              A100/251 A100/147 A102/222 B2/142 BV/147 BCV/145 M3/145 M102/145 M111/770 L101/760 T222/HL722 M111/770 no B3/C3!