What is the best solder for re-flowing solder joints on these old radios?

Discussion in '"Boat Anchor" & Classic Equipment' started by KD0YSX, Oct 6, 2021.

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  1. KD0YSX

    KD0YSX Ham Member QRZ Page


    I am wondering what people here use, and why. Found a couple of wiggly capacitors and reflowed them, but not delighted with the outcome.

  2. KF5FEI

    KF5FEI Ham Member QRZ Page

    Define older.

    Lead-free solder has been used on many products for at least the last 20 years or so. It can be a real pain to reflow, especially if your iron won't get hot enough to melt it. Adding leaded solder will help, if you can get it hot enough.

    If we are talking *old*, with point-to-point wiring, your iron may not have enough wattage to heat the joints and melt the solder properly.
    K1LKP likes this.
  3. WA5VGO

    WA5VGO Ham Member QRZ Page

    Kester 44 63/37
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  4. WA1GXC

    WA1GXC Ham Member QRZ Page

    There is expensive solder and not-so-expensive. There is a difference.

    63/37 mix is superior to the old standard 60/40 and was adopted by industry in the 1960s as the high-standard of choice for military and critical-applications. Because of the magic and weirdness of metallurgy,
    63/37 is termed "eutectic" and cools in a more uniform manner with less susceptibility to 'cold-joint' and physical fracturing.

    Kester's "44" solders have a quite-high (3.3%) rosin-core content. I have found with old stuff (WW II military, 1950s-1960s gear) with dull, ugly and sick-looking joints it's best choice to re-do a chassis/socket/term. strip
    connection. I completely melt-out much of the old stuff, fill-up the new terminal with fresh, let it blob and fall to the chassis if there's enough physical clearance, and fill the new connection with a small amount of fresh, good solder.

    There are numerous other brands of good quality, but lesser fraction of rosin. MG Chemicals, great Canadian outfit, has good 63/37 but chooses 2.2% rosin as standard which is quite adequate and good for making brand-new work.

    Leaded-solder prices have gone thru the roof. If you're fortunate, there'll be hamfests soon in your area. That's where I pick up solder, usually 1-pound rolls from some big engineering outfit contractor (probably walked out the back
    door in someone's knapsack.)

    If you find "Radio Shack" brand 60/40 as surplus, it's quite good quality, made in USA but usually pretty thick.
    I now always use the real thin stuff, .031-.032 inch. Use on big terminals, great for printed circuits alike.

    Lousy solder from across the sea is false economy. The metal came from your neighbor's bathroom demolition job. It heats lousy, flows lousy, is lousy.


    Addendum: I have Drake gear from late 1960s-early 70s. Despite high standards for design,
    production, materials, assembly, I've had more than a couple solder joints found fractured , fail, show
    themselves to be 'cold' at RF. Hard to believe, but true. I found 2 tube-socket connections that had been wrapped--got past the inspector--
    but had never been soldered.

    Always loosen, spray, and re-tighten ground-lug screws, to prevent odd RF issues.
    Last edited: Oct 6, 2021
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  5. KD0YSX

    KD0YSX Ham Member QRZ Page

    Thanks everybody!
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  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Last edited: Oct 6, 2021
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  7. KK9W

    KK9W Ham Member QRZ Page

    And if you need to keep that rosin flux in one place without running all over the place for something in an awkward spot you can leave a bit of liquid flux in a bottle cap and set it out over night and it should be tacky and thick the next morning. Then you just use a tooth pick or scribe to apply the flux to the spot you need it and it will stay in place while you make solder smoke.
    KA9P, NE3J, K1LKP and 1 other person like this.
  8. K6BSU

    K6BSU Ham Member QRZ Page

    I also recommend using liquid flux to re-heat old solder joints.
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  9. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Or...use paste flux :)
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  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Last edited: Oct 6, 2021
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