Model Railway Forum

If touching the solder joins makes the lights work yet touching the springs has no effect kinda suggests the solder join/s are the issue. There is such a thing as a “dry joint” which often forms in the sort of blob you have the surface of the solder oxidises and results in a poor or non-existent connection.

When soldering do you melt a blob on the tip of the iron and then apply it to the joint? If so then there is your problem. Once the flux has burnt off then the solder and the items being soldered oxidise and no amount of application with the soldering iron will work. When you apply the solder to the iron the smoke given off is the flux burning off as you you then move to apply it to the work more burns off leaving nothing to do what the flux is needed to do which is to suspend the oxides in the liquid of the flux.

The correct technique is firstly to have a properly tinned iron (a thin silvery layer of solder on the tip - not a blob) If your iron is not like that then again you will have problems and need to clean the tip and re-tin, this has been covered several times on this forum. Secondly, apply the tinned iron to the join and hold for a count off 1-2-3, this brings the joint up to the fusing temperature for the solder, then apply the solder which will then flow easily around the join.

You say that your soldering temp is 400deg. C which seems unnecessary high. If you are soldering in situ then maybe the axles and wheels are acting as a heat sink. Not all metals solder well and if those springs are stainless steel that may also be an issue and as suggested earlier giving the springs a bit of a clean will help.

Richard

Hi Richard - I usually have the iron at 350c - the bit is a bit grubby - is there a special way of cleaning the tip before tinning? Sandpaper or a small file will clean the tip, but is the tip coated when produced as new? I am awaiting delivery of one of those wire-wool tip cleaners. I've not had problems with soldering in the past - I did read that solder (I use 60/40 lead) can go off after time? Barry

I use one of these https://www.amazon.co.uk/DroneAcc-Solde ... 789&sr=8-8 Plus a wipe on a damp sponge as I solder keeps the tip in first class condition.
My temp-controlled iron with lead content rosen cored solder 60/40 runs at 375C. Had no issues to date. But lead-free solder needs a higher temperature. However, what the digital display shows and what the actual tips temperature is, is anyone's guess!

My soldering guide is here viewtopic.php?f=9&t=110 if you haven't read it.

I don’t think solder can go off Barry but it can tarnish.

bulleidboy wrote: ↑Thu Apr 21, 2022 8:54 am Hi Richard - I usually have the iron at 350c - the bit is a bit grubby - is there a special way of cleaning the tip before tinning? Sandpaper or a small file will clean the tip, but is the tip coated when produced as new? I am awaiting delivery of one of those wire-wool tip cleaners. I've not had problems with soldering in the past - I did read that solder (I use 60/40 lead) can go off after time? Barry

Hi Barry
A lot depends on how bad the grubbiness is, lightly oxidised and those “Brillo pad” the brass things will do the trick, next is tip cleaner which basically is a flux mixed with powdered solder, but in all my years of soldering I cannot say I have been pleased with the result. Finally, there is abrasion, but as you allude modern soldering irons have an iron carbide coating and abrade that off and for a while it will solder well before a cavity will appear on the end.

UNDER NO CIRCUMSTANCES USE FILES, GLASS PAPER OR EMERY CLOTH ON A SOLDERING IRON TIP.

If the previously mentioned methods do not work then it is possible to abrade without damaging the iron. Back in my work days our technician used a small BRASS wire brush attachment in a Dremel. Alternatvely one of those brass hand brushes used for suede shoes ( Does anyone wear suede shoes these days?) I have to stress only use a BRASS wire brush anything else will damage the iron carbide layer.

Richard

Walkingthedog wrote: ↑Thu Apr 21, 2022 9:43 am I don’t think solder can go off Barry but it can tarnish.

Correct, in damp conditions it can badly oxidise and can prove difficult to solder with because the flux cannot cope with the amount of oxides, applying additional flux helps. Most professionals would to avoid using it in that condition though.

Richard

I occasionally just pull a length of solder through some fine wet and dry to polish it. In my mass soldering days it never got a chance to tarnish.

Richard, Interesting point about NOT using a file on soldering iron tips as that is exactly the way we taught during my RAF workshop training!

teedoubleudee wrote: ↑Thu Apr 21, 2022 11:16 am Richard, Interesting point about NOT using a file on soldering iron tips as that is exactly the way we taught during my RAF workshop training!

So was I in my school days doing tinplate work but then we were using solid copper irons with copper heads about an inch square and probably three inches long and heated in a small gas oven. With copper heads that big you could afford a bit of filing to get rid of the oxides but on a 2-3mm fine tip remove the iron carbide and yes your iron will work perfectly fine - for a while! Then you will find a cavity develops in the tip requiring further filing back and at the same time making the tip wider. Some of the early electric irons had simple plain copper tips, I think Draper still make one like that and yes filing the tip was a quick way of removing oxides, in my early days I had one like that. However, modern iron carbide coated tips filing them clean is terminal, it could be down to poor quality copper as the base to the iron carbide but from experience I can tell you taking a file to a tip is only going one way.

Richard

I've given the tip a once over with the suede brush (yes we had one ), but I do have some spare tips/bits - this iron was the one that Brian (Flashbang) recommended many years ago - it came from Maplins and has served me well.