Trouble melting old solder...

[matt]

I'm trying to melt some old solder before fixing the wire and re-soldering the joint. The connection is in a phono plug so quite small. I'm using a fine tipped 15w iron which melts new solder easily but refuses to melt the old solder on the plug. I've fixed one of these plugs before and do not recall similar problems.

Anyone know about this stuff?

 

[Woody Alan]

Sometimes these small irons are just not up to the task. However I would suggest adding the solder that is liquifying to the stuff that isn't..sometimes it just needs the extra flux from the new to get things going. Depending on your experience with this sort of thing.... a sharp "rap" of the item on a hard surface will shift the molten solder off the item. I cannot stress enough the need for eye protection and having nobody else in the vicinity. You may have to put up with the odd minor burn from splashed solder ...nothing a bit of spit won't cure.
I have played with this sort of thing for years and to be honest a higher power iron will give results more quickly and if you also do the processs quickly, ultimately there will be less heat transfer to surrounding parts...as odd as that may sound.

Alan

 

[matt]

Thanks, Alan. I had considered buying a higher powered iron but the tip size seems to increase too. I've been scouting around for one with a variety of tips but I've yet to find a retailer that specialises in this stuff. I'd even thought about the gun type but I suspect they're a but unwieldy for the stuff I tend to do.

 

[RobertMP]

Is the tip of the iron tinned? ie wet solder coating the working part of the tip. if not it should be. Cleaning with a file will expose bare copper to let it take the solder.

15W should do a phono plug OK. Flux will make old solder melt again if it is a bit oxidised and resistant. You can make a bit of desoldering braid with a bit of the sheath wire from coax with some flux wiped over it. Press the fluxed wire to the soldered part with the iron and it will wick off the solder - just take it away before it sets.

 

[Balbus]

Surely everyone knows . . . old solders never die.

 

[matt]

Thanks for the suggestions. I'll clean up the tip to start off with and then try getting some flux on the case.

 

[Night Train]

If you want a small tip on a powerful iron then get a gas powered iron, they get really hot and have an assortment of tips. Mine has a 2mm slash cut tip, a 1mm point, a small bow torch for silver soldering and a hot air blower for heat shrink. I bought it from RS Components many years ago.

 

[RogerS]

Are Weller still going? They had variable tips. Also worht buying one of those solder sucker thingies to suck up all the old molten solder first so you stand a better chance of new clean solder and not a dry joint.

 

[tekno.mage]

Actually old solder can be problematic and not flow well - depends how it's been stored. I keep my reels in plastic bagsto minimise oxidation and have some that are erm... about 20 years old and still working ok.

For removing old solder from a previously soldered joint, you usually need to add new solder to get the old stuff to flow, then remove the whole lot with a solder sucker. It sometimes helps to use a larger bit for de-soldering (especially connectors) than you would for making a new joint.

Yes, Weller are still going. I have several of their irons (the magnetic tenmperature controlled type with the seperate mains transformer) and you can get bits in a huge variety of sizes & tempertaures for these. The irons & transformer units are expensive new (>£100) but can be picked up fairly cheaply second-hand on ebay and parts for them are still available - try RS components, Farnell or Rapid Electronics. I have one weller iron with a black transformer that must be 30 years old and is still working & spare parts are still available for it.

tekno.mage

 

[xy mosian]

Weller gun, fantastic, it has the added bonus of styaing where you put it when putting it down. Unlike the more recent Antex 15w jobs, where the cable is too stiff for the weight of the iron and it moves as it wishes. Some sort of cradle is essential, prefferably with heat sink to be in contact with the tip when cradled. If the cradle has a wet sponge to wipe the tip of the iron after each joint, so much the better, it will take away any excess flux which might otherwise erode the coating of the tip.
Solder sucker also essential, but take it apart when you get it to familiarise yourself with it. You may well need to do this quite a lot as you use it for cleaning.

xy

 

[woodbloke]

Some soldering iron bits are pre-tinned and should no account be filed, this just removes the surface and allows the solder to erode the copper. Just clean it on a damp cloth to remove all the gunge - Rob...(ex Plessey apprentice) who used to work in the business many, many years ago

 

[RogerS]

.... Rob...(ex Plessey apprentice) ....

Wow, that's going back some :wink: Mind you, I was trained on valves !

 

[RobertMP]

Some soldering iron bits are pre-tinned and should no account be filed, this just removes the surface and allows the solder to erode the copper. Just clean it on a damp cloth to remove all the gunge - Rob...(ex Plessey apprentice) who used to work in the business many, many years ago

Coated tips are good but if like me you only use the iron occasionally the coating gives up after a few years and you have no choice but to file the tip to get it working properly

 

[woodbloke]

.... Rob...(ex Plessey apprentice) ....

Wow, that's going back some :wink: Mind you, I was trained on valves !

You didn't work on this then did you Rog? :lol: - Rob...hat, coat, already moving :lol:

 

[Jake]

I bought a nice Metcal iron a few years back when I was building more hifi than I do now. Much nicer to use than even a good Weller, and they can go for a song on ebay with a little patience (at least they did back then, £25 or so, virtually NOS).

 

[bodgermatic]

I second the Metcal, an excellent iron.

 

[matt]

Cleaned the tip and tried adding some flux to the solder to melt it. It simply won't melt... I've de-soldered many joints in the past and never had this problem. I'm used to old solder being more troublesome than new solder but this stuff is unbelievable. I'm beginning to suspect the iron.

I may invest as the tip on my current (Weller) is getting short and the grub screw that holds it is broken...

There was a time when I wanted one of the gun types but I'm beginning to think it will be too cumbersome for some jobs, even with a small tip.