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.

2 thoughts on “Tektronix AM503: Balance Pot Bushing

  1. I guess that making a part for an antiquarian product of an uncertain age using measurement units long banished from the majority of the planet is quite appropriate ;-)

    1. Sometimes you know it’ll have hard inch units, so ya just roll with it.

      The lathe has switchable displays that spend very little time showing inches: gotta exercise ’em!

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