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Thread: About "Cold" Solder Joints

  1. #1
    Bacteriaolgoist GuitarDoc's Avatar
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    Default About "Cold" Solder Joints

    After looking recently (in person and at pictures on the forum) at many wiring jobs in guitars with problems, I felt the need to give all of you do-it-yourselfers a little practical advice/information that (hopefully) will help you along the path to becoming soldering gurus. Or maybe at least to have more successful wiring jobs with fewer problems. Most wiring problems are due to making incorrect wire connections...a hot wire to ground, a ground wire accidently touching a hot lug, a wire to the wrong lug on a 5-way or a pot, or a totally missed connection. I'm not going to say anything about that. But a lot of problems I have seen are because of that notorious "cold solder joint".


    "Cold" is a relative term. 350 degrees F is hot enough to give you a nasty burn, so you can consider THAT "hot". But it's not hot enough to melt 60/40 solder, so you can also consider that "cold", (you need a sustained temperature of at least 370 degrees F or 188 degrees C).

    There are two main ways to create a "cold solder joint".
    1. An iron that just isn't hot enough to melt the solder;
    2. A large heat sink which "pulls" too much heat away from the joint. This is the intended purpose of a heat sink, to protect delicate items from getting too much heat. But it is not good when it robs the joint of getting the heat that it needs to melt the solder and to heat the metal hot enough to make that solder flow like water onto it.

    Ultimately those two really amount to the same thing, but they can be resolved in two different ways.
    Obviously, #1 can be resolved by getting a more powerful iron. I consider 40 watts to be a minimum when soldering multiple wires to the back of a pot.
    #2 is related to #1 in that the more metal you have (many individual wires, large gauge wires, large metal surface like a pot, and a large amount of solder necessary to cover all of that metal), the more powerful/higher-wattage your iron needs to be in order to maintain the necessary heat at the joint.

    When you try to create a neat uncluttered looking job by putting many wires together into one large joint on the back of a pot, you are inadvertently creating a heat sink preventing the metal from getting hot enough. Then to make matters worse, you add more solder (more heat-sucking metal) to the joint in an attempt to make sure you have a "good" connection. This is actually defeating your purpose, and assuring a cold, ineffective connection.

    Unless you are soldering very thin wires, like the ones that come from pickups, it is best to have multiple joints of just one or two wires on the backs of pots. OK, I admit that it may not LOOK pretty to have 5 or 6 solder "blobs" on the backs of your pots, but "pretty" is NOT what our objective is. The correct electrical functioning of our guitars IS. Oh, and make sure you heat the pot (and the wire) primarily, NOT the solder. When the pot is hot enough, IT will melt the solder onto it and the solder will flow like water creating an intimate electrical connection between all the parts of that joint.

    No more cold solder joints. No more frustration trying to figure out what's wrong with your wiring when "everything is correct". No more wasting your time posting multiple threads when you could be playing your fine guitar.

    But be assured, the good members of this forum are here to help if you need it. We actually look forward to helping you whenever we can.

    OK, I'm done.
    Last edited by GuitarDoc; 10-01-2019 at 06:33 AM.
    Originally Posted by IanBallard
    Rule of thumb... the more pot you have, the better your tone.

  2. #2
    Mojo's Minions JB_From_Hell's Avatar
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    Default Re: About "Cold" Solder Joints

    I’m extremely thankful for the soldering class I took in college. Still haven’t bought one of those sweet Pace stations, though.

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    Mojo's Minions dystrust's Avatar
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    Default Re: About "Cold" Solder Joints

    Quote Originally Posted by JB_From_Hell View Post
    I’m extremely thankful for the soldering class I took in college. Still haven’t bought one of those sweet Pace stations, though.
    Those are pretty awesome, but maybe overkill for most of us. I've had a Weller station with an adjustable iron for the last 5-7 years and it's amazing. Of all the guitar related things I own, it's really the one I wish I'd bought years before.
    Quote Originally Posted by crusty philtrum View Post
    And that's probably because most people with electric guitars seem more interested in their own performance rather than the effect on the listener ... in fact i don't think many people who own electric guitars even give a poop about the effect on a listener. Which is why many people play electric guitars but very very few of them are actually musicians.

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    Super Toneologist DavidRavenMoon's Avatar
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    Default Re: About "Cold" Solder Joints

    I had a nice Hexicon soldering station back in the late 70s. Got that when I worked for the ITT Defense Communications prototype lab.

    These days I use a couple of Aoyue 937+ soldering stations, which is a copy of a Hakko. I keep it set at 400F

    The problem with a lot of amateur solderers is they are using under powered irons. They dont work well soldering to the backs of pots and stuff. And stay away from lead free solder if you can help it!


    Sent from my iPhone using Tapatalk

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    Mojo's Minions masta' c's Avatar
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    Default Re: About "Cold" Solder Joints

    Quote Originally Posted by DavidRavenMoon View Post
    The problem with a lot of amateur solderers is they are using under powered irons.
    Exactly.

    This a good and much-needed thread!

  6. #6
    Mojo's Minions
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    Default Re: About "Cold" Solder Joints

    I know just the recent thread that inspired you doc.
    And yes, there was a lot wrong with just about every joint in that job, so a tutorial on 'how to' is really what a lot of even more experienced forumites could use.

    Maybe a couple of pics showing what the solder looks like with a cold joint, and then and a well heated job. It would be easy for the people then to know as they are doing the wiring.

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    Imperator of Indignation idsnowdog's Avatar
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    Default Re: About "Cold" Solder Joints

    Stone cold solder and cold, cold sweat. Running down the back of my neck.

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    Administrator Mincer's Avatar
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    Default Re: About "Cold" Solder Joints

    This reminds me. I need to get a hotter iron. I think mine is 35 watts...an old Radio Shack one.
    Dave, Ambassador/Writer/Artist for Seymour Duncan

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    Bacteriaolgoist GuitarDoc's Avatar
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    Default Re: About "Cold" Solder Joints

    Quote Originally Posted by AlexR View Post
    Maybe a couple of pics showing what the solder looks like with a cold joint, and then and a well heated job. It would be easy for the people then to know as they are doing the wiring.
    Excellent suggestion. I'll work on it this weekend and see if I can get some good (and bad) examples to post.

    Yes, a picture is worth 1000 words. And when you're learning soldering techniques, maybe even more.

    Thanks, Alex.
    Originally Posted by IanBallard
    Rule of thumb... the more pot you have, the better your tone.

  10. #10
    Bacteriaolgoist GuitarDoc's Avatar
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    Default Re: About "Cold" Solder Joints

    Quote Originally Posted by Mincer View Post
    This reminds me. I need to get a hotter iron. I think mine is 35 watts...an old Radio Shack one.
    This is similar to the one I'm currently using. IMHO it is way, WAY better than the small Weller that has been mentioned many times. Yes, more expensive. But, I'm continually amazed at how well it maintains its temperature when soldering multiple wires to the back of pots. It's got enough power (700 watts) to automatically keep the temperature that you set it at (up to 480 degrees).

    https://www.amazon.com/Smartxchoices...qid=1570022739



    And if you're strapped for $$, here's a good 60 watt station for half the price.

    https://www.amazon.com/dp/B07GZHN7NX...NsaWNrPXRydWU=

    And if you're REALLY strapped for $$, here's a 60 watt adjustable iron for about half that peice.

    https://www.amazon.com/dp/B013JM4AW4...xpY2s9dHJ1ZQ==


    So, now you don't have any excuse for not upgrading to more power.
    Last edited by GuitarDoc; 10-02-2019 at 07:38 AM.
    Originally Posted by IanBallard
    Rule of thumb... the more pot you have, the better your tone.

  11. #11
    Administrator Mincer's Avatar
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    Default Re: About "Cold" Solder Joints

    I think I know what my next purchase will be. Thanks for the links!
    Dave, Ambassador/Writer/Artist for Seymour Duncan

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    Gear pics and more on my Instagram.

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    Mojo's Minions masta' c's Avatar
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    Default Re: About "Cold" Solder Joints

    My old RadioShack iron just stopped working well. Been a good 15+ years.

    Just for fun, I grabbed this one to try:

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    It's definitely cheaply made, but might work well...who knows! If it falls apart, I'll look for a deal on a RadioShack station on eBay or grab one of these fixed-watt jobbies from Hakko and a couple spare tips:

    https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

  13. #13
    Bacteriaolgoist GuitarDoc's Avatar
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    Default Re: About "Cold" Solder Joints

    Wow, for $11 you can't beat that iron. And so what if it only lasts a year or two.
    Originally Posted by IanBallard
    Rule of thumb... the more pot you have, the better your tone.

  14. #14
    Imperator of Indignation idsnowdog's Avatar
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    Default Re: About "Cold" Solder Joints

    It's a combination of low wattage iron and no flux.

  15. #15
    Tone Member Tone Meister's Avatar
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    Default Re: About "Cold" Solder Joints

    Quote Originally Posted by DavidRavenMoon View Post
    I had a nice Hexicon soldering station back in the late 70s. Got that when I worked for the ITT Defense Communications prototype lab.

    These days I use a couple of Aoyue 937+ soldering stations, which is a copy of a Hakko. I keep it set at 400F

    I think you guys must mean 350 and 400 degrees C.

    The next biggest problem with poor heat transfer is a tip that is too small. I use a pretty large chisel tip for guitar work and can heat up the back of a pot faster that you can say it. The quicker you can "get in and get out" the less chance of melting wires or damaging switches, jacks, or pots.

    I run my iron between 750 - 800 F when doing guitar work amd work very quickly.

  16. #16
    Bacteriaolgoist GuitarDoc's Avatar
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    Default Re: About "Cold" Solder Joints

    Quote Originally Posted by idsnowdog View Post
    It's a combination of low wattage iron and no flux.
    That will give you the best opportunity for the worst cold joints.
    Originally Posted by IanBallard
    Rule of thumb... the more pot you have, the better your tone.

  17. #17
    Toneologist
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    Default Re: About "Cold" Solder Joints

    Great info. I invested in a Hakko FX-888D a few years ago. That thing has been awesome. I keep it on 750 degrees most of the time for guitar work.

  18. #18
    Bacteriaolgoist GuitarDoc's Avatar
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    Default Re: About "Cold" Solder Joints

    Another word of clarification:

    60/40 Solder melts at 188 degrees C (370 degrees F).

    Keeping your iron over 400 deg F is overkill unless you are using a low watt iron that can't sustain 400 deg while soldering to the backs of pots, or using a very small pencil tip which also doesn't hold much heat when in use.

    If you're using a more powerful iron that can sustain 400 deg F and using a chisel point which also holds more heat while in use, you don't need to keep it that hot. It just burns up your tips quicker.

    My station is very powerful and maintains a constant temp while in use and I use a chisel tip so I keep mine set at 350-400 deg F. When I'm soldering to the backs of pots I may raise the temp setting to 400-450 deg F. I had my station set to about 420 deg F. when I did the soldering in the photos in the other thread. As you can see, it was PLENTY hot. No problem getting the solder to flow thin as water on the backs of pots.

    If soldering is part of what you do in your work, you owe it to yourself and your customers to get a good solder station...to yourself because your soldering will go much faster and smoother with no frustrations; to your customers because they can see your soldering and your work will look great and they will be impressed with everything else you do that they can't see.
    Originally Posted by IanBallard
    Rule of thumb... the more pot you have, the better your tone.

  19. #19
    Tone Member Tone Meister's Avatar
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    Default Re: About "Cold" Solder Joints

    350F - 400F isn't anywhere hot enough for professional soldering. Perhaps you mean 350C - 400C.

    Here is an article that is consistent with my own soldering experiences (40 years).
    https://www.build-electronic-circuit...g-temperature/

  20. #20
    Tone Member Tone Meister's Avatar
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    Default Re: About "Cold" Solder Joints


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