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Soldering question - Pots

Discussion in 'Pickups & Electronics [BG]' started by Crusher47, Apr 14, 2014.

  1. Crusher47

    Crusher47 Tattoo'ed Freak Supporting Member

    Apr 12, 2014
    Fort Worth, TX
    Dumb soldering questions, refer to picture below....

    1. Both volume pots, the post on the right where it is bent back towards the case of the pot with a glob of solder.... does the post have to actually touch the case itself or will the solder be enough if it's touching both?

    2. I've also seen it where someone used a piece of wire and soldered the wire to the post... is that a "preferred" way of doing it or just personal preference?

    3. Speaking of wire, again referring to the picture below, there is a black line going from the right most pot on each volume pot, you do solder a wire from pot to pot, in other words, that black line should be a black wire, correct?

  2. Hey there,

    I'm not an electrical authority, but feel pretty confident about how I would approach your questions above...

    1. As long as the connection is sound, the solder that connects that post with the case is sufficient--some posts bend easier than others.

    2. Electrically, it makes no real difference. I suspect personal preference, or perhaps an aversion to bending posts too far.

    3. Those are grounds to ensure that the whole assembly is grounded properly with itself. Some setups might rely on some other method (like foil backing on the pickguard, or a metal guard of some sort that the pots bolt through), but this way, the assembly will work correctly even if sitting outside the body cavity, unattached to a pickguard. The color of the wire insulation is black, but that's only a visual reference for ground--the wire doesn't know what color the insulation is.

    All the best,

  3. jefkritz


    Oct 20, 2007
    iowa city, IA
    yep. agree with shanebo.

    one other thing - IME you don't really need to solder to the pot housings at all. as long as all the ground are connected and that is connected to something grounded (like the strings via the bridge) you should be good. It doesn't hurt, but i've never had bad results when replacing pots and not soldering the lugs to the housing. YMMV etc
  4. Crusher47

    Crusher47 Tattoo'ed Freak Supporting Member

    Apr 12, 2014
    Fort Worth, TX
  5. Soldering terminals to the chassis is a bad idea! Always use a piece of wire. The reason being that it is a PITA to get the terminal desoldered and pulled back, later on, if you need to disassemble the pot.
  6. bassbenj


    Aug 11, 2009
    While some (including some factories) for their own reasons disagree with me, I DO NOT recommend soldering to the backs of pots as shown in the diagram. Just use simple ground wires instead and don't bother with the pot backs.

    The reason is that soldering to to pot backs can put a lot of heat into the pots and that will make them "scratchy" much sooner than otherwise. And another reason is that using the pot backs as ground is a bad idea because they are just crimped onto the threaded part that mounts the part. A crimp is NOT a long-life permenant connection as it can corrode over time. In a jazz bass (as shown in your diagram) the jack body (which is THE ground for the bass) is bolted onto the control plate and THAT becomes the ground plane. The pots screw into that which also grounds their bodies.

    So why solder to the pot backs? Well the idea is that if you cheap out and DO NOT shield the cavity, you can sort of get away with just the shielding provided by the control plate and the pot covers. No it's not perfect, far from it, but we are trying to save pennies here, OK?

    What YOU want to do is shield the WHOLE cavity with the shield up over the top to contact the control place PLUS a wire going from the shield (copper or paint) going to the body of the output jack. If you do that you'll block all hum AND whether or not the pot backs are grounded won't matter a bit. Hence no overheating is needed.

    Bottom line: Shield your bass and don't solder to pot backs. Ground wires inside the cavity will do the job. Hence with no soldering to pot backs there is no bending of lugs and any damage that might entail.
  7. ReidK

    ReidK Jst sy n t lsy cmprsn.

    I'll cast another vote for not soldering to pots. It's only done to make up for lack of shielding, and I shield all my instruments. Even if the cavity isn't fully shielded, if the pots are solidly attached to a metal plate or a good foil-backed pickguard, the pot bodies are grounded.

    I always thought the whole lug-bending thing was pretty lame.

  8. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Well, maybe. It's very important that the pot cases are grounded. This can be accomplished by using lock washers that make a good connection with the cavity shield, as long as the shield is properly grounded. My preference is to run a grounding wire to the case of each pot. It doesn't hurt them if you use a little spot of flux on the case so the solder adheres quickly - just don't get the case any hotter than necessary.

    If the cavity is not shielded, then you can do it another way. Solder the grounding wire to each of the lock washers that will go under the pots. I think Roger does them this way. You avoid heating the case.

    I recently installed a Pope Flex Core in an EBMM Stingray 5. The pickguard has an aluminum shield over the cavity, but the shield is not grounded to the cavity shield. This leads to hum whenever you touch the metal knobs, which are mounted on the pickguard. The solution was to put a small square of copper shielding material on the aluminum, then solder a lead to it and run it to the grounding lug in the cavity. Since the knobs all made contact with the aluminum through their lock washers, the connection was made - no more hum.

    Some pots actually have a tab on them specifically for attaching a ground wire.
  9. The manner in which you choose to make the connection has no effect on the shielding in the instrument. The connection must be made in one way or another, however, in order for the pots to be wired to do what they are supposed to do.
  10. uOpt


    Jul 21, 2008
    Boston, MA, USA
    Don't ask the potentiometer manufacturers. We were never supposed to solder on the back.

    The proper way to ground the case is to screw the whole thing into a grounded metal plate.
  11. Crusher47

    Crusher47 Tattoo'ed Freak Supporting Member

    Apr 12, 2014
    Fort Worth, TX
    Thanks again everyone, I just finished installing new Pups on my Jazz Bass last night, and it works! Very happy with the results.
  12. Nice job!
    Crusher47 likes this.
  13. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    guitar companies like fender and gibson have been soldering to the backs of pots for a good 75 years now; i'd say it was a decently proven technique.

    done right, there's no problems with overheating the pot.
    Stone Soup likes this.
  14. ReidK

    ReidK Jst sy n t lsy cmprsn.

    Really? Connecting the pot case to ground doesn't shield that pot more effectively than leaving the case floating? Are you saying that in a bass with an unshielded cavity, leaving the pot cases floating won't add any noise? I don't see any other way to interpret the sentence above, but that certainly hasn't been my experience.

    Perhaps I wasn't clear. My points were 1) if the cavity is fully shielded, the pot cases don't need separate grounding arrangements, and 2) soldering to the back of the pots is, at best, redundant if they have a solid electrical connection via a plate or shielded pickguard that is grounded. Are you disagreeing with one of those points, or with something I didn't say?

    I thought it was clear that I was talking about shielding, and the necessity (or lack of it) of soldering to pot cases. In this sentence you seem to be talking about the signal ground, and yes, obviously, that connection has to be made, via wires if not pot cases. I said nothing to the contrary. My point that it's never necessary to solder to a pot case still stands.

  15. ReidK

    ReidK Jst sy n t lsy cmprsn.


    Careful, solder fumes are addictive!

  16. The purpose of the connection between the third terminal of the pot and its chassis is for the chassis to ground the end of the resistive element. NOT for the end of the resistive element to ground the chassis. If you should choose to ground the end of the resistive element to some other ground point, the shielding in the instrument will be unaffected.
  17. ReidK

    ReidK Jst sy n t lsy cmprsn.

    I didn't say or imply that soldering the third terminal to the pot case would ground the case. I didn't say anything about the third terminal at all. I don't know what you think you're replying to, but it's not anything that I wrote.

  18. That's what this thread is about.
    AGH likes this.
  19. ReidK

    ReidK Jst sy n t lsy cmprsn.

    This thread is about the third terminal?

    If you ignore the diagram that the OP posted (which shows several different things soldered to pot cases), and ignore posts #3, #6, #8, #10 and #13, none of which were mine, then yes, I can see how you might come to that conclusion. Those things form the context of my postings in this thread. If you're ignoring them, you should probably ignore my postings as well. In fact, I rather wish you would.

  20. Crusher47

    Crusher47 Tattoo'ed Freak Supporting Member

    Apr 12, 2014
    Fort Worth, TX
    Sorry if my dumb questions started a debate and/or any heated arguments...that was clearly NOT my intention. I appreciate everyone's help, experience, advice and insight. This place is the best!

    I will be soldering up another set of pickups either today or tomorrow, keeping my fingers crossed the last set I did was not a fluke :)