Stuck Stuff: Gibson's Tin-Can Jack

More stuck stuff. A slightly unusual one, this week.

If you work on (or if you have) an older Gibson you’ll occasionally come across a guitar with a curious output jack.

The Switchcraft shielded jack, sometimes used in Gibsons, has to be 'opened' to work on.

From outside the guitar, all seems normal. Try to get at the jack, however, and you find something weird.

Back in the day, Gibson sometimes used Switchcraft shielded jacks

That there’s a Swithcraft Shielded Jack. Essentially, it’s a jack in a tin can. The outside of the can is connected to the ground sleeve of the jack to ‘shield’ the internals.

A super-quick recap on shielding

As your guitar signal passes along it’s signal wire, it’s susceptible to nasty interference from all around you. If you ‘wrap’ that signal wire inside something that’s connected to ground, you can capture a lot of that interference and shift it away before it gets to your signal.

That wrapping might be in the form of a braided outer ‘shell’ around a wire. It might be a metal cover over the volume and tone controls. And it might even be a tin can over the output jack.

Opening a Gibson Shielded Jack

So, you need to work on that jack but how do you get into the damn thing. It’s not super-obvious and, once you know how, it’s a little tricky.

There’s no screw threads or grub-screws holding this guy together. Instead, the ‘cap’ part (with the jack attached) has two small detents on its side. These slot into two corresponding holes on the ‘body’ of the tin can part.

Knowing that is one thing but getting them apart is another.

I’ve found the best way to do this is to first grip the body of the tin can with a suitable tool. You’ll need something with jaws that open wide enough to accommodate the jack cylinder. I use an adjustable pliers (I know them as pipe-grips) which seems to work nicely.

Grip the jack carefully and you can prise the cap off

Grip the cylinder housing with the tool, close to the cap part. Then use a flat-head screwdriver to prise off the cap. Bear off the pliers jaws and ‘twist’ the screwdriver blade against the cap. You’ll probably have to go back and forth to opposite sides a couple of times but the cap will eventually come free.

It should go without saying that it would be easy to crush the tin can with the pliers. Keep this in mind and watch your pressure. You want just enough to grip that cylinder as the screwdriver does its work.

Because I’m not gripping too hard, I’ve never had a problem marring the outside of the cylinder but pop a bit of masking tape on it if you want to be safe.

Gibson shielded jack - Free!

Also you’ll see some masking tape on the side of the guitar I’m working on here. That’s protecting the guitar finish because the jack hook-up cable is too short to pull it any further out of the body. I could have de-soldered the cable from the guitar but I just wanted to clean and re-tension this jack so I saw no point messing with original solder.

Closing it up again

That’s pretty easy. Line up the detents in the cap with the holes in the body and push them together. Done.

They’re not exactly common but they’re not too hard to find if you ever need to replace it. Try a search for Switchcraft ¼” shielded jack and you should find something useful. Ebay’s a good place to start (affiliate link). They come in stereo versions too.

So, that was a slightly niche Stuck Stuff but one day, someone’s definitely going to thank me for it.