Soldering Commercial Guitar and Amp Pot Bodies, Chassis Too!
This chore does not require sanding or a huge iron, and it can be done without unduly heating the pot. I did use a Weller SP-23 25W iron and sometimes still do, but my favorite is a 30W NexxTech I got at Radio Shack; not because of the extra 5W, but because of the coated tip which works better than the copper tip on the Weller.
There are probably better irons out there, I'm just showing the size.
I prepare the pot before trying to solder a wire to the body. The preparation consists of getting a thin layer of solder in the target area, really just tinning a spot, using a slightly different method than that often recommended.
When building an amp, I'll prepare all the pots on the bench before hand.
The iron tip is applied briefly to the target area to preheat it, a minuscule drop of solder flux is applied to the target area and then the iron returned to that position. The solder is touched to the iron tip so the smallest amount of solder possible is on the tip, barely 'tinning' the tip and then the tip is moved slightly about the heated area ('scratching') until the solder spreads out on the pot forming a thin layer as the iron is moved.
Once there is a thin layer of solder bond to the pot body, an appropriately sized puddle of solder can be applied and left to harden.
The object is to get a small amount of solder to bind to the pot, when this is done, it is easy to get solder to bind to solder.
Where I differ with some people (for this particular application) is in the application of solder to the iron instead of the work piece, the reverse of how electrical soldering is commonly done.
This is an application of techniques learned in grade school where we made projects such as storage tins and cookie cutters with sheet iron joined using old fashioned irons heated in a forge and bar solder with paste flux. It is more akin to sheet metal soldering than the making of electrical joints.
The process takes longer to explain than to do.
When the pot is in place, ready to solder a wire to ground it, the iron is placed against the hardened puddle of solder. As the puddle softens the wire is pressed into place with a tool and then the iron is used to briefly heat the wire, the tool then returned to the wire to hold it in place while the puddle hardens. More solder could be applied at this stage if necessary, but with solder, just use what you need to form the joint, extra is a waste and could be in the way later on.
Because the job is done in steps of 10 or less seconds, the pot doesn't get as hot as it would if I tried to do it in one step.
In the case of pots such as CTS which have a lot of information stamped on the back, you might want to consider soldering to the edge of the pot so the information of the back remains available for future reference.
When there a lot of grounds to go to one spot, I'll make a ground tab out of copper flashing. Before soldering it to the pot, I'll drill a small hole for each wire plus a couple extra just in case. This tab allows the wires to be attached one at a time with just a touch of the iron so the there is no chance
of over heating the pot.
So far I've been speaking to pots but a similar principle applies to amp chassis.
When I found myself with the desire for solder ground points on a chassis, I thought I would need big iron and maybe even gas, so I asked about it on a kit building site. Not one reply was made to how to make a solder ground point , everyone said drill and bolt - don't you hate it when people ignore your question?
I took my stripped chassis outside, roughed out a spot and applied my 80 watt iron for what seemed a very long time and then I applied flux and eventually solder. With the exception of the longer application of heat, the method turned out to be the same idea I use on pots. Tin a target area by 'scratching' at it with an iron to which a drop of solder has been applied, then make a puddle. My first attempt was very crude but as I developed a feel for the chore (and much patience ) the next 2 spots were easier, quicker and looked professional.
Next I tried with unscratched surfaces, and then I switched to the smaller irons and got the same results.
So I do the chassis the same way I do pots, except more time is required due to the thicker metal.
While I provided multiple ground points I found once I got going, that I only used two. Both adjacent to a power transformer bolt. I had made a ground point tab out of thin copper flashing, which once tinned, easily soldered to the chassis although it was also bolted via the transformer mount. I ran all my grounds to these 2 points.
Topic: soldering to chassis (Read 10626 times)