Rudimentary soldering questions What am I doing wrong?

Old 09-22-22, 07:34 AM
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Rudimentary soldering questions What am I doing wrong?

I'm 60. Been soldering electronics intermittently since 10 years old. Started with a radio shack kit using a soldering gun like in the pic. Too much heat they told me / that's why the kit didn't work after I was done.

Fast forward to now. Trying to solder some speaker wires, using a 100w soldering gun I got at a garage sale.

I know long wire will conduct heat away.

What am I doing wrong? Soldering iron gets hot. Will melt solder if touched to it directly.

I have the tip heating the splice. Solder not melting unless I get right next to tip.

Meanwhile plastic jacket is charring from the heat!

I cleaned thip of iron when hot with wet rag.

I cleaned / tightened the connections of tip / iron.

Use a smaller iron? Larger gun?

By the way, this is 14 AWG speaker wire. 1 lead is silver color, 1 is copper color. They run to speakers outside under an eave (doesn't see water, but does see humidity) to the finished basement with dehumidifier - not all that humid in general

The cable is likely 15 years old?

The copper color wire is greenish under the jacket along the entire length. Is that just age? never saw that before. Or humidity wicking along the length of the 100' run?! The middle of the run and the ends are the same greenish / copper mix. I'd wonder if that is part of the soldering problem. But the silver conductor is solver still / no oxidation.


charring of insulation

Old gun, but it DOES get hot / melts solder

What the joints look like before soldering

The copper colored leads have green oxidation.
Old 09-22-22, 08:01 AM
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Rosin flux will make the solder flow onto the wire quicker. I have found that touching a splice that has been fluxed with a small blob of solder on the tip of the iron will flow very quickly and not char or melt the insulation. The tip of the iron needs to touch the wire to heat it. Solder flows to the heat. Just dropping the solder blob onto the splice will result in a cold-solder joint that is mechanically and electrically unstable. No rosin flux provides results like yours.

I use a rosin flux pen. Clean the oxidation. The copper should be shiny.
Old 09-22-22, 08:09 AM
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The green is corrosion.I think it is a reaction to something in the plastic insulation. I have seen this before.The wire is still fine.
However you won't solder that wire unless you get it clean and shiny.
Old 09-22-22, 08:53 AM
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One conductor appears corroded as Joed mentioned. Moisture/humidity can pass through many plastics so your wire is likely just suffering from old age. It will be difficult to impossible to solder that wire. Using a acid rosin flux will help greatly but it must be thoroughly cleaned after soldering as the rosin is corrosive and the connection may eventually fail.

With clean, shiny wire I use no clean flux. It isn't as good on dirty or difficult metals like a acid flux but it doesn't have to be cleaned off afterwards and won't corrode the wire.

It also looks like you need to clean the tip of your soldering iron. When the tip is up to temp drag it quickly across a damp sponge to wipe away the old solder and dross (bad solder). If you still have trouble getting the solder to melt with the tip you may need to clean it on some fine sandpaper.
Old 09-22-22, 10:37 AM
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Soldering 101...
Solder iron tip must be tinned
All wires must be cleaned
All wire should have flux
Be sure electronic solder is used, not mending solder
Never cool with breath, let cool naturally and do not move until cold
It won't take much heat to solder stranded wire together
Old 09-22-22, 11:00 AM
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What solder are you using, solder for electronics is different from solder for copper pipes.

I solder green/corrosion wires all the time, no flux, no problems.
Old 09-23-22, 06:28 PM
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I would tin the bare conductors first before twisting them together. If they won't tin first, then the splice won't take solder either. Put some flux on them will also help.

If insulation melts or chars before the bare wire takes solder, then you went too far and need to back up and prep things as the previous replies have indicated.
Old 09-24-22, 11:54 AM
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With inexpensive wire it is very porous and allows water to pass thru the insulation and the green is moisture reacting with copper. It is very hard to solder corroded wire. You need enough heat to burn the corrosion but that usually melts the insulation.

I replace alarm contacts all the time that are attached to copper wiring that has corroded around window areas. I use a razor knife to scrape the corrosion off the wire. I'm working with wires that are only an inch or two long so I can't risk insulation burns. It is not easy. Does take some practice and experience.

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