Power Supply Banana Jack Misfit

After butchering that fancy Tektronix test lead thing for the SMD tweezers, I hung the bitter end in my cable tangle. Turns out I needed a power cord to bring up the brassboard of the Wouxun GPS interface, so I soldered it up, went to plug it in, and … the Tek plugs didn’t fit the plated supply jacks.

Power Supply Banana Jacks
Power Supply Banana Jacks

Now, if I had to choose whether Tek plugs are oversized or Made In China jacks are undersized, well, you can probably guess my answer.

Turns out that the jacks should be 4 mm ID, which is actually a 5/32 hard-inch size because banana jacks date back to the days before millimeters became a force to be reckoned with. They were actually 3.8 mm ID, which wouldn’t usually matter except for the fact that the Tek plugs have a nice solid bullet end that’s just about exactly 4 mm OD.

So I chucked up a 5/32 inch drill, perched the power supply on a block of wood (to clear the fuse & cord in on the back panel) on the drill press table, and hand-held it while clearing out the holes with a low spindle speed. You can see the nice, shiny brass inside those jacks in the photo; they used to have lumpy silvery plating inside that was probably responsible for much of the 0.2 mm shrinkage.

The jacks also don’t have the usual crosswise hole near the base to accept a bare wire, which is an occasional nuisance. I was tempted to drill that hole, but decided I’ll leave that project for another time.

3 thoughts on “Power Supply Banana Jack Misfit

  1. That’s a nice, clean fix.

    I wish it were that easy to touch up my Simpson 260, which features a 5/8″ spacing between the “-” and “+” input jacks, instead of the 3/4″ spacing that is standard on pretty much every other meter known to man.

    Every time I try to plug in a set of test leads wired to a standard dual banana plug, I curse a bit and wonder if a little quality time with the rat tail file followed by some JB Weld wouldn’t put things right :-)

    1. a little quality time with the rat tail file

      Or a few months with a 3D printer to conjure up a hideous adapter… [grin]

      I ordered my AADE L/C meter with the optional 3/4 inch jack spacing and haven’t ever regretted it!

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