Cable repair and construction jig

[skod]

If you are going to be building a studio, I think that you might find it to be extremely useful to make a soldering jig. It'll pay for itself in speed, ease of assembly, and lack of burns very quickly! Here's a picture of mine. It's a simple aluminum plate with male and female XLR, TRS, 5-pin mini-DIN, and RCA connectors all mounted on it. I can clamp that to my workbench, and then plug the connector I'm working on into the mating connector on the jig- that keeps it from going anywhere.

I also cut a slot in the jig that tapers from 3/8" to 1/8" to hold the wire while I tin it. I strip it, drop it in the tapered slot so that it can't go anywhere, tin it, then pull it out of the slot and solder it to the connector.

You can see all the connectors- the MIDI cable off the back is bridged across all of them in the correct pin order, so that the far end of a cable under construction can be plugged into the other side of the cable tester and tested while the solder is still cooling: regardless of what set of connectors the cable might have. It's a great timesaver. You can also see a cable dropped into the tinning slot, already stripped and ready to tin. Plug the connector insert from _any_ flavor of connector into the mating connector on the jig, and it'll be going nowhere while you solder it up.

The other thing you might notice is that the XLRs and mini-DIN are installed in what looks like upside-down orientation. This was done so the the solder cups on Neutrik connectors came out facing up- making them easier to tin and the final cable assembly much faster.

It's just a random scrap of 1/8" aluminum with some connectors on it. Build yourself one of these and cable building and maintenance becomes a very quick and easy task. You can do it with only two hands! The way I figure it, having the right tool for the job is priceless: if you do more than 30 or 40 cables in your life, you're wasting time not to have one of these. I've probably put several _thousand_ connectors through mine, after building 3 studios now...

[MysteryTramp]

Very nice! I've been trying to figure out a way to jig up and that looks like a compact, elegant solution.

Do you loop the cable through that slot to hold it in place while soldering?

Trying to figure out how to secure the cable has been kindofa question mark here.

[skod]

*Tinning* is the key. Let's use the XLR as an example. I plug the insert into the mating connector on the jig. Then, I strip the cable conductors, and drop the cable into the slot, so that the bare copper wires and the virgin pins on the XLR are pretty much side-by-side. I then grab the solder in one hand, and the iron in the other, and start tinning. I'm not trying to make a joint: i'm trying to make sure that the wire and the pin are both perfectly wetted with fresh, clean solder *before* they ever get near one another. I tin the conductors so that they are completely wetted with solder- not blobby, but smooth and shiny. I tin the connector solder cups so that they are smoothly filled with fresh, shiny solder. I then put the solder down- I'm done with it!: the rest of the job will be done with reflow soldering.

Pick up the tinned cable in the hand that's not holding the iron, drop the freshly tinned conductor onto the nice pocket of solder in the freshly tinned solder cup on the pin, apply the iron to the _cup_, and watch as the solder *reflows* to form a perfect joint. Hold the heat on long enough to make sure the solder on the cable conductor has also reflowed and merged with the molten solder in the cup. Pull the heat off, and make sure that things stay stable until the solder has chilled completely. Viola': a perfect joint that only took two hands.

Tinning is the key: the fresh, oxide-free solder-wetted (tinned) surfaces reflow to perfection. Trying to do this without tinning one or the other, or without refreshing the tinning on old/used wire or connectors, leaves oxides or oils (fingerprint oils, for example!) or other crap on the surface, and can lead to cold joints or worse. Fresh tinning, and the use of just enough solder, is the key: the conductors and the connector flow together smoothly and without drama.

In short: _always_ tin, whenever possible. The rosin flux is there to provide one hell of a surface cleaning _just before the bond is made_: let it do its work.

I'll see if I can put some pictures together that might make this make more sense...

[Slackmaster2K]

Skippy, this is a great thread!

[ola]

Just two things that newbies may miss, I know I did:

1. The soldering iron should heat the metal you're soldering, then place the solder on the metal and melt it that way. Don't put the solder on the soldering iron drip it on the metal.

2. Always use solder with flux in it, unless you really know what you're doing and the application calls for non-flux solder - in our case, it never does. I once bought some cheap solder and didn't think about the flux. It was like soldering with poop. I ended up making jewelry out of it and bought som decent solder.

[skod]

Ola is exactly right, and brings up a couple of good points. The iron should heat the wire and the pin enough for the solder to melt and flow. If you drop hot solder onto cold wires or pins, the solder that hits the surface will chill before it wets or the flux can do the cleaning. This is called a cold joint, and it will be intermittent, mechanically weak, and may even cause noise or distortion. Bad news. Get the work hot enough to melt the solder and get the flux to flow!

For electronic soldering around the studio, you need a fairly small iron. 25 watts is just fine, and actually even a little bit large for most patchbay/instrument/cable work. 35 watts might be necessary if you anticipate doing a lot of heavy soldering (like copper tape for shielding guitar pickup cavities, where the copper will sink too much heat away from the joint area with a smaller iron). You'll almost *never* need more than 25 watts: too big an iron will get you into more trouble than you want, as the extra heat will get to places you don't want it to go to.

Soldering iron tips: long, skinny, slender, conical, for our style of work. You won't need many: I've been using the same long conical tip on my Weller iron for 4 years, certainly many thousands of joints (two studios worth!). With care and cleaning, they're pretty long-lived. The tip will slowly erode, as any copper in it goes into solution in the solder- but that's thousands of joints down the road... Keep a moist sponge at hand for cleaning the tip occasionally as you go, so that fried flux and spooge does not build up on the tip (which can lead to inclusions of spooge, which can be just as annoying as cold joints).

Use great care if you shop for your soldering equipment at a hardware store like Home Depot. Most of their soldering gear is intended for plumbers: million-watt guns and nasty, disgusting acid-core solder, either of which will disintegrate a printed ciruit board at first glance. Not applicable to our needs. Radio Shack is a better bet, if you don't want to mailorder from a real electronics supply house.

Solder with a rosin flux core is essential. Kester 44, 60/40 rosin-core solder is the best there is for everyday general purpose use. It's been the number 1 selling electronic solder since World War 1: it ain't broke, so they ain't fixed it! Or, if you really want to do some turd-polishing, Kester 62: 62/36/2 silver solder with the same rosin core. That is twice as expensive, but is *righteous* stuff for audio work, especially if you have gold-plated connectors or PC board traces to deal with. Whichever type of solder you get, the 0.025" dia stuff is easiest to work with, even though it looks leetle teeny at first. The small diameter solder gives you very precise control of how much you use for each joint.

Lastly: splurge for a roll-holder like you see in my picture. This eliminates the need to wrestle with the solder, or chase the spool down as it rolls away. Little things like that make the job go much faster: crucial when you are making as many joints as are needed in a typical studio installation...