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Odd Lots


  1. Jack Smith says:

    I use tamper detection paint on certain filters I build and sell. These are narrow band top coupled resonator designs with trimmer caps that must be sweep aligned in a test fixture and will likely not meet spec if disassembled to “see what is inside.”

    The tamper detection paint comes in a small plastic tube and is relatively thick, almost a paste consistency but it shrinks and becomes brittle as it dries — it can easily be removed to back the screw out but leaves no doubt that the seal has been broken.

    It’s available in a variety of colors at around $3 per tube. See

    1. Back when I was a Xerox tech rep in the 70s, we used something called Glyptal to keep screws in certain locations from shaking loose. It also showed us sometimes that, yes, somebody had adjusted that screw in the past.

      1. Jack Smith says:

        Glyptol is still available – if you are a traditionalist you will wish to purchase the red version. Look for MG Chemicals 4228 Red GLPT Insulating Varnish on Amazon. About $9.50 for 55 ml.

        I bought a bottle (55ml) from Allied Radio a couple years ago and the shipping charge was $20 or so because it’s considered a hazardous substance and must ship with special packing. (It’s flammable.) It’s good to hold the copper windings to a coil form or to retain BNC lock nuts if you are out of locktite.

        Hot rod engine rebuilders use Glyptol to seal the inside water passages in the engine block and you can buy a quart of it for $40 or so.

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