Applying solder to the back of Potentiometers

[essexbasscat]

Hi BC

I'm in the process of upgrading the electrics on my road worn P bass with a kit from Charles guitars - RS superpot + paper / oil capacitor + CTS tone pot.

When I applied solder to the back of the volume pot this morning (for the earthing connections), it became a matt silver slab, instead of the nice shiny silver block that denotes a nice solder joint.

The original Fender solder joints on the back of the pots are nice silver solder blobs, so it can be achieved

I made sure the soldering iron heated up a fair bit before starting the job, but still it didn't do the job properly. Maybe I need a hotter iron ?

The other concerns are transmission of all that heat to;
- the pot itself. Will it damage the pot ?
- the capacitor. I'm considering using a small free standing vice as a heatsink. It has a small crocodile clip which I intend to attach to the capacitor leg. When it comes to attaching the capacitor to the back of the pot, I intend to solder a small piece of wire to the back of the pot first, let that cool, then solder the other end of the wire to the capacitor leg, thus hopefully avoiding transmission of too much heat associated with the process of soldering the back of the pot

Any ideas folks ?

Thanks BC

[Beer of the Bass]

I find it often helps to scuff up a small area on the back of the pot with fine sandpaper immediately before soldering, then it will take the solder much more easily. IMO the old style tin/lead solder is much friendlier too.

[RhysP]

[quote name='Beer of the Bass' timestamp='1479035253' post='3173397']
I find it often helps to scuff up a small area on the back of the pot with fine sandpaper immediately before soldering, then it will take the solder much more easily. IMO the old style tin/lead solder is much friendlier too.
[/quote]

This.

The newer solders are a swine to work with compared to the old tin/lead ones.

Edited November 13, 2016 by RhysP

[mybass]

Over heating the pot may damage/ warp the interior tracking and some make of pots are easier to solder an earth to than others. As advised by 'beeronthebass', try scuffing the pot a little ( I scrape with a small screwdriver sometimes but make sure to blow away any dust or metal bits) to achieve a better receptive spot for the solder to adhere to.

[Grangur]

Matt or shiny makes no difference, this can be down to the solder. What matters is that the solder lies nice and flat to the body and doesn't look like a bobble standing on top of the pot.

[markstuk]

[quote name='RhysP' timestamp='1479035817' post='3173404']
This.

The newer solders are a swine to work with compared to the old tin/lead ones.
[/quote]

this +1.. Although you can still buy old style solder, it just can't be used in RoHS products..

[MoonBassAlpha]

A bit of extra flux usually helps too. It de-oxidises the pot surface and makes the solder flow/wet better, as long as you get sufficient heat into the pot casing.

[Twincam]

As others has said.
But also getting a good iron helps. Temp variable. And the right tip for the job, I find a slightly larger tip is better for the back of pots rather than a fine soldering one.
Also get some of the older lead solder as said.

[essexbasscat]

Thanks BC

I checked the wattage of the iron I used earlier and found it to be 25 watts. I changed it for a 40 watt iron and this helped a great deal, especially after leaving the iron to heat up for at least 15 mins before using it.

Now the tone pot isn't working

[Twincam]

[quote name='essexbasscat' timestamp='1479062236' post='3173642']
Thanks BC

I checked the wattage of the iron I used earlier and found it to be 25 watts. I changed it for a 40 watt iron and this helped a great deal, especially after leaving the iron to heat up for at least 15 mins before using it.

Now the tone pot isn't working
[/quote]

Sometimes the heat can kill them especially if there old or been through soldering a few times.
Its best imo to do it as quick as possible to avoid heat soak.
My method is to set the iron at a higher temp. And get in and out as quick as possible.

[paul_5]

I use a file on mine to get down to the bare metal, then use a temperature controlled iron and good old 60/40 lead/tin solder. Works every time.

[dyerseve]

[quote name='paul_5' timestamp='1479072736' post='3173757']
I use a file on mine to get down to the bare metal, then use a temperature controlled iron and good old 60/40 lead/tin solder. Works every time.
[/quote]

Me too with plenty of flux and temp on my Weller set to 450c with a large tip.