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Issue with solder not sticking to back of pots

NickInMesa

NickInMesa

Jan 1, 2009
3,397
51
57
Mesa, Arizona
#1
I am rather good at soldering. Seriously, I am.

I have several irons, from the 10W pen style, to the temperature controlled type.

But I always seem to have issues making solder stick to the back of the pot and always end up with a nasty blob of solder, and it's embarrassing, seriously.

I scratch the surface prior, clean it up with acetone to remove any varnish, but it does not quite work well and always end up applying a lot of heat to solder the ground wires and terminal.

I have tried different types of solder, it's becoming aggravating.

And those are good pots from Stewmac, by the way.

Any idea?

Besides looking bad and also being a pain to do, the result is fine, but bad solder sometimes mean bad contacts.
 
#2
I've never had a problem. I have encountered some pots that aren't meant to be soldered to though. Normally I'll put the solder on and then reheat it and add the wires. You could always just run your grounds to the jack instead of soldering them to the pot.
 
#5
I've found it can be difficult too. Solder just doesn't wet to certain metals well. It sounds like you're doing a good job of scuffing/cleaning the metal (I use a scotchbrite pad). It may be your iron. I've been using an Edsyn 951SX at home for soldering electronics with good success. At work we use a few flavors of Metcal irons. We routinely solder to heavy-copper circuit boards (10-20oz and up) and sheets or bars of copper with those irons.

Good luck!
 
#11
Munjibunga said:
The piece has to be hot for solder to adhere. I don't think a 10-watt iron will get the pot hot enough (well, it will, but it will take a long time). My lowest power iron is 25 watts, but when I'm soldering to pots, I break out the gun. You have to be careful not to overheat the pot and damage it.
Click to expand...

Exactly. I have a good array of irons. The 10W is actually a 12W and it works great for circuits with heat sensitive components as even with a heat shield, a 25W is already bad.

But I have wrecked one pot with a 50W iron once.

I have done the tinning of the back but it does not always work as expected.

I am thinking going forward of only grounding the one terminal to the back of the pot, with a wire connecting all the ground terminals, and one wire into some sort of a "hub" where are the ground wires would connect.

It really does not matter where the ground wires connect, actually.

willsellout said:
I've got a 60 watt weller iron and I use a fat chisel tip @ about 750 degrees when I solder to the pots . No problems for me. I normally rough it up with 400 grit sandpaper beforehand.
Click to expand...

I believe you are using too much heat and may have damaged a pot or too? 750 degrees, I hope it was Farenheit :)
 
#12
I recently got a used Bartolini preamp that had grounds connected to a washer rather than the back of the pots., which then is making contact to a pot. Worked well, easier to solder, and easier to swap a pot down the road.

Not sure of any other implications of doing it that way.
 
#13
A little flux is all you need. No need to rough it up. Heavier areas of metal need a bit more heat to make it flow well, but only get it hot enough to flow the solder well. Not too hot that you burn it. Give your solder iron a chance to get hot before you stick it in there. A little practice helps if you are not used to doing it, but once you have done it several times, it's a peice of cake. Watch out for the wires. Don't blow on the solder, or you may cause a cold solder joint. I use flux for making cables too.
 
#14
blockinlay said:
A little flux is all you need. No need to rough it up. Heavier areas of metal need a bit more heat to make it flow well, but only get it hot enough to flow the solder well. Not too hot that you burn it. A little practice helps if you are not used to doing it, but once you have done it several times, it's a peice of cake. Watch out for the wires. Don't blow on the solder, or you may cause a cold solder joint. I use flux for making cables too.
Click to expand...

Why didn't I think about it?

I've soldered copper pipes in the past, even some wet ones.

DUH!
 
#15
Flux is your friend. +1 on no need to scuff, though I don't see the harm in doing it that way, either.
 
#16
Munjibunga said:
The piece has to be hot for solder to adhere. I don't think a 10-watt iron will get the pot hot enough (well, it will, but it will take a long time). My lowest power iron is 25 watts, but when I'm soldering to pots, I break out the gun. You have to be careful not to overheat the pot and damage it.
Click to expand...
+1 gun. Rough the back of the pot if needed to remove any oxide buildup and tin it quickly with lots of heat. Use a rosin core solder so you don't need to fool with extra flux. Then it's easy to stick the wires on. Typically I can tin the back of the pot with a 300 watt gun in about 1-2 seconds, then use an iron or the gun to attach wires later.

Too small an iron can damage the pot just as easily as a big old gun if you leave it on there long enough. It's the total heat that goes into the pot that causes the damage, not the wattage of the iron or gun. The higher the wattage, the more quickly you have to work, is all. I used to marvel at my grandfather doing fine soldering with a giant gas heated iron.

It's also a good idea to blow a little contact cleaner into the pot after finishing soldering. Sometimes bits of rosin can get in there 'cause they're not sealed.

Still, if the pot body is aluminum or something, it's gonna be awfully hard to solder to. :eek:
 
#17
Ric5 said:
Scratch up the back of the pot ... and flux can help. But be careful with flux it can damage the pot.
Click to expand...

There is really NO reason to use flux nowadays. A good quality solder has all the flux you need to make a proper solder joint. I've been involved in electronics since 1971 and probably have used flux since 1972.

And if you insist, DO NOT use plumbers flux. It will corrode your connections.
 

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