Hello, and a little soldering help?

Been a member for a while, but this is my first post. Recently I've been making some experimental interconnects, from a wide variety of cable types. Even with my very humble system the differences can be quite remarkable. My biggest success so far is with a very thick copper cored coax - basically a solid copper bar! Anyway, I've now hit a snag - the reasonable quality RCA plugs I've been using up until now are quite easy to solder, but now I've found some new, and very substantial, plugs that I'm struggling with. The problem is pretty standard - the large amounts of metal involved are sucking the heat away from my solder, but if I apply more heat I melt the insulators. I'm attaching a photo. The coax core goes inside the pin part of the plug, so an added frustration is having to solder into a little hole. Anyone got a solution for this, before I cook another one?

 

Here's what t do ....

get an RCA socket, and from the centre pin solder a peice of copper from the centre conductor of the cable shown, about 50mm, twist around a pencil to form a coil and solder the other end to the ground of the socket. Clamp the socket in a vice or make a small back plate to hold the socket. Now insert plug in socket , when you solder it the heat is drawn from the insulation to the heat sink, of course this is not infaliable but helps greatly.

 

If I'm trying to solder large bits of metal i try to use the lagest physical size of solder bit that i can fit easily into the space available. I usually use my gas soldering iron as it has lots of different tips and can go go quite high heat wise. I make sure that both bits of metal are very clean and oxide free. I then marry up the two bits to be soldered and add some flux paste or liquid. I find that with a large solder bit that is fully up to heat ( let it heat up for at least 10 minutes before use) there is a bigger 'resevoir' of heat in the tip and this makes up for the heat sink effect from the parts to be soldered. The use of the extra flux really helps to make sure the solder flows well.

If you can 'Tin' both peices seperately before putting them together then you ahve already done the hard bit. Pre-tinning is always the best way to go for this type of job from my own experience.

One brand of Flux paste that works brilliantly is Frys 'Fluxite', unfortunately it is a very active acidic based flux paste and so you would never find me using it on electronic circuits . Multicore aslo do a 'Safe' liquid flux pen for use on electronic circuits, it works like a marker pen with a felt application tip.
Isn't it a shame that the nastiest chemicals are always the best .....

 

Thanks to the both of you - I'll take both sets of advice, i.e. fabricate a heatsink and get some decent flux. Going to have a wander into electric town tomorrow anyway as I... err... need a couple more RCA plugs.

 

I have used these RCA plugs for co-ax cables successfully to make digital interconnects. Maplins do them in 3 different diameters and if you get the right one, it will grip tightly over the copper foil. It is designed to do just that; so need to solder.

The inner core can be soldered through the slot in the pin.

Finnish off with a heat-shrink over the cable and the plug barrel.

 

Maplin now sell a much superior co-ax cable made by Shark.

"The cable core is 0.5mm diameter OFC Copper plated in 80µin Silver. The Silver plating takes advantage of the phenomenon of “skin effect". “Skin effect" describes the tendency of ultrahigh frequencies to be conducted on the surface of the wire as opposed to through the wire's total profile."

Part no. N61AR. £2 per meter.