(Un)soldering the backs of pots (e.g. pickup wiring)

[MattG]

Not directly a pedal question, but I know many around here have changed their electric guitar's pickups and/or pickup wiring.

I went to simplify the wiring of one of my guitars (change a 5-way pickup switch to 3-way). The stock wiring basically uses the metal case of the pots as a ground bus. IOW, there are fairly large blobs of solder that connect wires (or the shield braid) to the pot housing.

How do you un-solder these big solder blobs? Holding my iron to the pot or solder blob (even with a generous amount of flux paste applied), didn't get the solder hot enough to flow. There is just so much effective metal volume (pot housing + wire/shielding + solder blobs) that it soaks up all the iron's heat. (Like a PCB without thermal reliefs!)

I suspect if I simply held the iron on the housing long enough, the solder would eventually flow. But I wanted to check here before doing that to see if there is perhaps a better way.

Thanks!

 

[spi]

Holding my iron to the pot or solder blob (even with a generous amount of flux paste applied), didn't get the solder hot enough to flow.

I haven't had that issue--usually the solder blob will melt pretty quickly. What iron are you using?

 

[MattG]

I have a Circuit Specialists CSI-Station1A, which they don't appear to sell any more. It's a 40 watt unit. I bought it in 2011. Link to the manual. The tip is probably as old as the unit itself, maybe it's time for a new tip?

 

[drgonzo1969]

I have had similar issues with soldering to pots. Use the biggest tip you have for your iron and then I usually apply a little fresh solder to help get the old stuff heating up faster but ya it takes a while to heat up. I always get uncomfortable with how long it takes but you are right on.

 

[Gordo]

+1 on the above. The hot setup (no pun intended) is one of those big janky industrial looking irons but if you don't do this kind of stuff on a regular basis it's kinda overkill. Generally though if you can get the solder moving with a fresh batch it will pay off in spades to try to get rid off the rest of the blob with a solder sucker or wick. The trick is not to get the pot too hot or you risk buggering up the innards. Once you get the spot clean then try and plan your regrounding by twisting/soldering as many ground wires together as you can so you only have to revisit the spot once.

If you watch a lot of guitar repair videos it looks like they're using a pool cue for a soldering iron and it works well for loosening frets as well.

 

[jwin615]

Assuming your iron gets hot enough, you'll also need a broad spade/flat tip or at least a bigger chisel tip. From the manual, like looks like one of the hakko 936 ripoffs. I still use one for my daily driver and it works fine on pots with a decent sized tip. If your tip is that old, yeah, it's time. I'd recommend getting hakko branded tips. Depending on the age and origin of the guitar, you may be dealing with lead free solder. Maybe even some of the early crappy rohs stuff.

 

[Feral Feline]

Another option for really recalcitrant pot-solder that I've had to employ is to cut off the wire as close to the pot's solder-blob as possible, then pick a clean unblobbed area of the pot to solder to — ignoring the old solder completely (well, after trying to get it gone at least once). Give the pot's clean area a cleaning ie scuff it then IPA and fresh solder and wire won't take as much to heat up — less likely to damage the pot, too.

Job done, then have another sip of the IPA.

 

[Alan W]

I’ll add on to @Feral Feline; after you’ve clipped off those wires, you may have more luck with getting rid of the blob, since there aren’t as many heat sinks (aka wires) stuck to it. Before you buy a new tip, those little tins of tip cleaner paste really work well.

 

[Joben Magooch]

Another option for really recalcitrant pot-solder that I've had to employ is to cut off the wire as close to the pot's solder-blob as possible, then pick a clean unblobbed area of the pot to solder to — ignoring the old solder completely (well, after trying to get it gone at least once). Give the pot's clean area a cleaning ie scuff it then IPA and fresh solder and wire won't take as much to heat up — less likely to damage the pot, too.

Job done, then have another sip of the IPA.

That's kinda what I was going to say. If I use a good sharp pair of flush/diagonal cutters you can get things pretty clean with that alone - cut the wires off but also I've found if there's enough solder left on the pot for the cutters to "grab" you can cut right through that as well. Ends up cutting/scraping the bulk of the leftover solder off the pot. The rest is pretty easy to get up then (if you even want/need to bother at that point)

 

[MattG]

In this case I don't want to cut the wires off the pot, at least not all of them. Two of them are actually the shield braids from the pickups. The pickups' "hot" wire is shielded. So the wire comes from the pickup cavity, and at that point it's closest to one pot. About two inches of the shielding is peeled off, and soldered to the pot (and trimmed down). That remaining length of (now unshielded) wire goes to the pickup selector switch. There's really not a lot of extra length to play with here, so cutting what little slack I have could make the job harder.

This is in a 2023 Yamaha Revstar Professional RSP02T (P90), FWIW. My goal is to simplify the wiring: the tone pot is a push-pull type that switches a "boost" transformer into the circuit. I never use it, and don't see myself ever using it. The current pickup selector is a 5-way, and I also don't use the 2 and 4 positions. So I want to basically have simple Telecaster-style 3-way wiring. I'm also flirting with the idea of a DIY passive coil get some hum cancelling effect.

Anyway, sounds like an appropriate first step is to get a new right-shaped soldering iron tip. Thanks everyone!

 

[spi]

I wonder if the solder they used is lead-free--that could mean it needs some higher temp to melt.

 

[GAStan]

Best method I've found is:
1. Large tip
2. Higher temp than normal
3. Clean then apply some Flux
4. Use a solder sucker, not braid
5. Work QUICKLY. Apply iron to solder. As soon as you see some of the solder flow use the solder sucker. Do not try to flow (melt) the entire blob of solder at once or the heat will spread and solder that has flowed will cool and solidify.
6. Allow tip ample time for the tip to reheat. This also allows pot to cool a bit so it doesn't get heat damaged.

Be patient, this is a technique that took me several tries to get right. When working with a low to medium powered soldering iron the heat energy in the tip quickly transfers to the larger mass of the pot and the heating element cannot produce enough heat to keep the tip at temperature required to flow solder. Hope this makes sense. I use a 100 watt iron and while it does make things easier I still have to use this technique on larger items.