Resoldering?

[bluzmn]

I recently got a '59-'60 Premier Twin 8. I "chopsticked" the whole chassis, and found that (almost) all solder joints of components to inputs and pots made a "crunching" noise when I poked them. That same "crunching" accompanied every note I played on a lap steel. I guess that means I need to resolder all those joints. My question is: do I need to suck off all the old solder with a solder sucker, and resolder with new solder, or can I just"reflow" the old solder?

[R.G.]

I recently got a '59-'60 Premier Twin 8. I "chopsticked" the whole chassis, and found that (almost) all solder joints of components to inputs and pots made a "crunching" noise when I poked them. That same "crunching" accompanied every note I played on a lap steel. I guess that means I need to resolder all those joints. My question is: do I need to suck off all the old solder with a solder sucker, and resolder with new solder, or can I just"reflow" the old solder?

You can reflow the old solder; the problem is usually that you also need a bit of flux to float the oxides out of the cracks while the solder is molten so the new joint will be smooth and continuous. It is simplest to touch a bit of fresh rosin-core solder to the old joint as you remelt it.

You do not need to remove the old solder. In fact, that makes you prone to getting flakes and dribbles of the old stuff down into the chassis from the desoldering.

Remelt with flux.

[Rhodesplyr]

R.G., I think that your advice is correct for the large majority of cases; however, I have run into a few cases where it was necessary to remove the old solder completely and even remove and reattach the wires. Those cases have mostly involved tube socket terminals where arcing through the bad joint creates a burned spot that doesn't respond well to reflowing the joint. I've had to do this on a couple of older amps--and on a fairly recent production Fender Deluxe Reverb.

On the issue of connections to input jacks and pots, heavier terminals can require a bit more time to heat up properly, so if someone was applying the soldering iron to each joint for the same amount of time, you can end up with cold solder joints.

[J M Fahey]

For that exact work and nothing else I keep an old 150W , wooden handle soldering iron, with a tip of solid copper as thick as my middle finger.
Forget needle tips, long life ceramic tips, etc, just a good old bar of copper, flat tips preferred.
Yes, it's tin-soluble and developes "cavities", I remember needing the benchtop grinding wheel often (we are talking late 60's) but there's nothing like it.
PS: remember those pops and cracks when close to pots , jacks and switches come not only from solder joints, but from dirty/rusted/pitted/worn contacts inside.