Soldering Buss Bars to Pots

[Coco]

I don't normally do this, but I was fussing around a specific TMB build and thought I'd try it and see if I could eliminate all hum. It didn't make much of a difference, but I had a heck of a time soldering the 22 guage buss bar to the back of the Alpha pots. I'm not happy with the soldering quality so ..

Any tips for doing a good job on soldering the buss bar?

P.S. there is no hum at all on the build.

[loverocker]

Roughing up the pot body (sandpaper/file) and using a big iron works best in my experience. But I avoid grounding through pot bodies in general.

[bitsandvolts]

Yeah, I had some trouble with a few cold solder joints on my sIII bus bar...my 30watt pen simply couldn't get the bar hot enough to get the solder to melt to it. Almost as if I were soldering to a heat sink...

I corrected the problem by whiping out my weller 100w/140w gun and forcing the issue with the 100w setting...

[rjgtr]

what loverocker said.

I also find that soldering the ends first helps. The pot mounted bus bar does make the amp look cleaner, but it is a royal pain to replace a pot. It is just so much easier to have a bus bar.

[phsyconoodler]

The coating on the pots needs to be removed by sanding them.Then the solder will stick to the pot.You don't need to use the 100 watt gun that way,which can melt the plastic components inside the pot.I usually add some solder to the pot first and then tin the buss wire,and it attaches easily to the pot.

[jersey_aaron]

I always thought this was a bad practice. Heating up those pots to such a high temperature can't be good for the wipers inside. If you have a pot that goes bad, then you're going to generate even more heat getting the pot out since the whole network is going to act like a heat sink. During that time, you'll probably disturb the joints on adjacent pots. If you've already got wires on that buss bar, you're also going to get them hot as well.

A lot of sheople think that whatever Fender or Marshall did 40 years ago is unquestionably the "right way" to do things. It's not. At least thats what this idiot from New Jersey thinks.

[Coco]

This is not something I do for the reason JA expressed. But in this case, I just wanted to try it and see. I think I'll remove it and see if there is any change in noise. I somehow doubt it.

[kd]

I don't usually like the idea of soldering to the pot but, if you need to do it, then as has been mentioned rough up the finish of the pot and remove residue. The ticket to getting a good joint without a large iron or alot of heat is to use solder paste flux on the surface of the pot regardless of wether or not the solder you are using has a flux. This will make the process a whole lot less painful.

Ken

[wiggle]

Some pots can not be easily soldered to even if you clean them up first. I think rosin helps but some old mil spec pots and some stainless body ones will not accept solder. If you dremel down to the brass you may have luck.

Good luck

[allynmey]

I for one like to use a buss bar across the pots. I find this will quiet down a noisy circuit. I take a dremel tool and lightly grind a little circle on the back of the pot and add a little solder. I lay the bar across the the cleaned area. I heat the bar until the solder melts and I see the ground circle "suck in" some solder and done. I verify resistance from every gound point on the bar and pot to my main power ground. That's it!

Allynmey

[Jlwctn]

KD sez:

"The ticket to getting a good joint without a large iron or alot of heat is to use solder paste flux on the surface of the pot regardless of wether or not the solder you are using has a flux. This will make the process a whole lot less painful."

Amen, Hallelujah! Flux makes a difference in soldering, no matter what you're soldering on. It helps with grounds, but it will also help in working on a PCB. You_don't_have_to_leave_the_heat_on_it_as_long. Cold solder joints become a thing of the past.

[Coco]

Update:

Well, I lifted the buss bar off the pots and there was no change in hum. In other words, the TMB was still silent. So, as a result, I won't use this grounding technique.

Thanks for all the tips. I'm sure there are others who will do this and you never know, some day, I may need to as well.

Cheers!

[Plexi]

You don't need a real big buss.. I use 18 gauge soild wire,which works fine.
And as was posted.. rough up the back..which i use steel wool,but hold the pot so nothing might get in the pot. Or i use a flat file. Then flux..and lay the chassis so the pots are in a more flat position.

The buss can be put on the pots, or along the back of the board..or inbetween the board and pots. The thing is.. if you notice. If the buss is along the pots..its a short ground off that pot..but a longer ground wire from the board if something off the board is going to the buss along the pots. I've been using the buss along the pots.. and the other grounds off the board go to sections of grounds. And the first chhannel has all its own grounds. This seems to work very well,nice and quiet with no hums.

Some things too, if you have a hum..you have to figure out if its a ground..or tube/cap or what is causing it.
But i just like short as possible ground runs.

Richie

[phsyconoodler]

Actually,Fender never used to do the back of the pot ground method.The lack of a ground buss of any kind is what causes noise problems in some older amps.There are exceptions to every rule.I say do whatever works for you.I like the buss wire because it leaves the pots free.The only thing is,with time,the metal the pot is attached to can oxidize and cause a grounding issue that is harder to trace.The buss wire looks neater in most cases and is easy to trouble shoot when the time comes.
Simple is good!