The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • Tektronix AM503: Balance Pot Bushing

    One of the Tekronix AM503 current probe amplifiers arrived without the panel bushing for the Balance trim pot. Back in the day, you could presumably order part number 350-0301-02 and have it delivered (most likely) by your local Tek representative:

    Balance pot panel bushing - Tek part listing
    Balance pot panel bushing – Tek part listing

    Those days are over.

    A few minutes produced a doodle with pretty-close measurements:

    Balance pot panel bushing - dimension doodle
    Balance pot panel bushing – dimension doodle

    The as-built bushing turned out just a smidge too long, so make yours a scant eighth of an inch. Maybe the Tek dimension is the overall length?

    An SLA resin printer might crank out such a thing, but it’s well below the looks-good / fits-well resolution limit of an ordinary fused-filament printer.

    Applying the mini-lathe to a 1/4 inch white acrylic rod produced a reasonable facsimile:

    Tek AM503 Balance pot bushing - front
    Tek AM503 Balance pot bushing – front

    The side view:

    Tek AM503 Balance pot bushing - side
    Tek AM503 Balance pot bushing – side

    Acrylic is definitely the wrong material for the job, but it came readily to hand while pondering the Shelf o’ Rods. Acetal would be better, as you could easily trim off the aforementioned excess length with a knife.

    All’s well that ends well:

    Tek AM503 Balance pot bushing - installed
    Tek AM503 Balance pot bushing – installed

    A dab of white acrylic adhesive around the raw opening holds the bushing in place and it looks good enough to me.

    The motivation for this boils down to having the bushing center the pot twiddler required to set the balance, which I must do every time I fire up the amps, even after waiting for the half-hour required to stabilize them at their operating temperature.