weird problem - pots not taking solder & getting "greasy"

[seanm27]

Hi you've all been super helpful to me lately. I just bought some new 500k pots from mouser.com and unlike other pots I've soldered to these ones really arent taking the solder at all and are becoming sticky and greasy.

 

It's really weird other pots I've used have been a pain but nothing like this, does anyone know what I can do?

[caver]

Please forgive me if you already know this stuff...

 

Make sure the solder tabs on the pots are very clean. Buff them with some very fine sandpaper or steel wool and wipe them with some alcohol. Make sure you remove all the buffing debris.

 

Also make sure you're using rosin core solder for electronics. The stuff from hardware stores is usually acid core and will not work well...if at all...for electronics. If it's still tough, try a drop or two of solder flux from Radio Shack. That's a good place to find the right solder too.

 

If it's still tough, maybe your soldering iron is dirty or not hot enough.

 

Good luck.

[irishstu]

Please forgive me if you already know this stuff... Make sure the solder tabs on the pots are very clean. Buff them with some very fine sandpaper or steel wool and wipe them with some alcohol. Make sure you remove all the buffing debris. Also make sure you're using rosin core solder for electronics. The stuff from hardware stores is usually acid core and will not work well...if at all...for electronics. If it's still tough, try a drop or two of solder flux from Radio Shack. That's a good place to find the right solder too. If it's still tough, maybe your soldering iron is dirty or not hot enough. Good luck.

 

I can't really add to that. Are you talking about soldering to the tabs or to the casing of the pot though? I got some push/pull pots once where the casing was made out of some metal that just wouldn't take solder, so I had to use a washer that would take solder instead.

 

Evidence of the shameful job I did here:

 

[amp_surgeon]

I assume you're soldering to the "can", since the tabs rarely have this kind of problem.

 

Alpha pots can be a little tough to solder to because of the lubricant that's left all over them. When you say they're getting "greasy", it sounds like lubricant is causing your problem. Clean the outside of the can with a little contact cleaner and rough them up a little with light sandpaper or emery cloth.

 

If you bought the Bourns "guitar" pots from Mouser, then you may have gotten some of the first batch of pots they received from Bourns. Those have a known manufacturing error, where the guys on the assembly line accidentally used zinc plated cans instead of the regular tin/steel cans. There's no way you can get solder to bond with zinc. Mouser won't take 'em back if you'll already soldered to them, but Bourns will happily exchange them if you tell them what happened. When I returned some pots to them I not only got replacement pots, I got a coffee cup and some guitar picks!

[seanm27]

Thanks so much everybody! Yes it is the can I'm talking about and I think you may be right about them being zinc since they are out of this world difficult.

 

However I am going to clean them, sand em, and flux em and see if that hellps at all.

 

Incidentally I was able to gerry rig the ground lines together and plug in the guitar and it works, but as you would guess it has horrible noise that mostly goes away when you touch the strings or the pot shafts.

 

Thanks again!

 

[EDIT] Actually they are not the bourne models they are just plain alpha pots so it is probly the factory grease and hopefully it will clean off.

[katillac]

My method:

Scuff surface

Always clean with denatured alcohol (methylated spirits to our friends across the pond, and rubbing alcohol works as well)

Be sure soldering iron is hot enough to melt the solder

If it's more difficult to solder (due to being pot metal with zinc in it), I use a flux pen to dab a little flux on the surface.

[irishstu]

Well even if they're zink, you can use the washer trick (thinking back, mine did have that zink look about them).

[amp_surgeon]

Well even if they're zink, you can use the washer trick (thinking back, mine did have that zink look about them).

 

Next time you're tempted to try the washer trick, try this instead:

 

http://www.mouser.com/Search/ProductDetail.aspx?qs=qhgJLQbFbXnvAZzpvvZwpQ%3d%3d

 

 

Ok, these lugs are made by Amphenol, and are actually intended to be used with panel mounting BNC jacks, but they work fine with pots. Just put them around the bushing when you mount the pot, and bend the tab back. It just about reaches the lugs on an Alpha pot, making it look like there's four lugs on the pot. We use 'em on fuzz pedals to provide a common "star" ground point. Look at the lug between the two pots:

 

[irishstu]

Next time you're tempted to try the washer trick, try this instead: http://www.mouser.com/Search/ProductDetail.aspx?qs=qhgJLQbFbXnvAZzpvvZwpQ%3d%3d Ok, these lugs are made by Amphenol, and are actually intended to be used with panel mounting BNC jacks, but they work fine with pots. Just put them around the bushing when you mount the pot, and bend the tab back. It just about reaches the lugs on an Alpha pot, making it look like there's four lugs on the pot. We use 'em on fuzz pedals to provide a common "star" ground point. Look at the lug between the two pots:

 

Thanks man, that's what I really wanted to use, but couldn't get my hands on any big enough at the time (it was 9 years ago). I'll know next time. Cheers.

[Barry Wuthrich]

I'm a newbie at this and am wondering.

 

Does anybody tin the back of the pot first? Or, melt a big puddle of solder first and then stick the wires in it?

 

The first time I tried it, I was using a pointed rather than a flat tip and ended up with a headache by the time I was done.

[Loudog99]

I do that. I use Alpha pots and they have a protective coating that you must sand off to have the solder stick. I use a 30 watt iron with a small chisel tip and have no problems. I tin the wires- then I tin the pot with a small drop of solder. I then place the tinned wire on the small drop of solder, place the tip on the wire and when it melts together, pull the iron away and hold the wire steady. DONE.

 

Lou

[seanm27]

 

I'm a newbie at this and am wondering. Does anybody tin the back of the pot first? Or, melt a big puddle of solder first and then stick the wires in it? The first time I tried it, I was using a pointed rather than a flat tip and ended up with a headache by the time I was done.

 

 

That is the technique I was using on my greasy pots from hell, but the solder would pool up like a mercury ball and even after it had cooled it would just roll off the pot.

[WRGKMC]

Scratching the surface with some sandpaper as Katillac mentioned then use a higher wattage soldering gun or heavy iron works. You need to heat the can first before applying the solder. Those littel pen soldering irons can barely heat the can hot enough and you wind up applying heat too long. The greasyness is either the solder flux or the pot is packed with conductive grease which lubricates them and gives them a plush feel when turning.

[seanm27]

Next time you're tempted to try the washer trick, try this instead: http://www.mouser.com/Search/ProductDetail.aspx?qs=qhgJLQbFbXnvAZzpvvZwpQ%3d%3d Ok, these lugs are made by Amphenol, and are actually intended to be used with panel mounting BNC jacks, but they work fine with pots. Just put them around the bushing when you mount the pot, and bend the tab back. It just about reaches the lugs on an Alpha pot, making it look like there's four lugs on the pot. We use 'em on fuzz pedals to provide a common "star" ground point. Look at the lug between the two pots:

 

Would a typical uninsulated ring terminal do the same trick?

[Barry Wuthrich]

 

Would a typical uninsulated ring terminal do the same trick?

 

 

Yes. I get them at Radio Shack. It's a 3/8'ths. It says 'ring tongues' on the package. Just make sure the tongue is long enough to clear the pot with the flat side facing away from the pickguard. (strat)

 

I ground everything to a separate washer and wrap it with electrical tape to avoid a ground loop to the shielding. That way, only one wire goes to the ring tongue signal return. It's an extra step, but if you need to change anything up later, you don't have to remove the pot.

[Barry Wuthrich]

 

I do that. I use Alpha pots and they have a protective coating that you must sand off to have the solder stick. I use a 30 watt iron with a small chisel tip and have no problems. I tin the wires- then I tin the pot with a small drop of solder. I then place the tinned wire on the small drop of solder, place the tip on the wire and when it melts together, pull the iron away and hold the wire steady. DONE. Lou

 

 

Thanks,

My Japanese strat has wires too short to go to a separate ring terminal. I tried it, and barely got the pickguard back on. It's a 62RI so the routing is much tighter on the electronics cavity.

 

I am having trouble with the volume pot, so I'll probably ground the wires back to the pot shell when I get it apart. I will try your technique and hopefully avoid the aspirin.

 

Sorry for the hijack, just kindof borrowin from the same expertise the original question addressed.

[Belva]

Maybe solder & shrink an extension to the wire? I like the ring terminal idea as it seems like a better idea than heating up the back of the pot. Def gonna try on my current build.

[katillac]

I have used a similar type terminal that's made for crimping to wires, except that I solder mine. They're aluminised copper, so they won't corrode like steel will.