Pot case grounding

[gtwirges]

Every amp layout I see has the grounds going to the case of the pots. Is there any reason to use the case of the pots? Or is just a convenient location to attach grounds?

Thanks

GW

[ampgeek]

Welcome!

It is the latter. Many of us run a bare, largish gauge (18 or so) bus bar that connects to the chassis at the input jack grounding point.

Going onto the pot case makes it very difficult to change the pot later on. There are commercially available connectors that connect mechanically with the body but also have an eyelet for a wire.

Cheers,
Dave O.

[eniam rognab]

yup all of Dave O. says and more,

not a good mechanical connection due to the fact that oxides will build up between the pot and chassis, thus lifting that 'ground' either intermittently or permanently, took humanity a while to realize this happens and thats when 'we' switched to the buss wire Dave mentioned.

everything seems to be a copy of everything in the amp world in some way or another... i dont know, Fender probably did this and so his DNA is in that amp somehow, like a shelter dog.... i dunno

buss wire,
neal

[gtwirges]

Thank you! That confirmed my suspicions, question arose from the recent purchase of some pots that solder will just NOT flow onto properly, no matter what I do. I was thinking about the buss bar idea exactly as you describe, just wanted to get some verification of the thought before doing the work.

Thanks again,

George

[Reeltarded]

Use a piece of 220 paper to scuff the pot. There are protective agents used on the metals and release agents (waxy oils) from the machining process. If it's stainless like PEC do a little of that, etch a drop with acid, wipe clean and get the torch out.

[eniam rognab]

a drop with acid, wipe clean and get the torch out.

will do immediately, have to call my dealer, i believe he is plying his wares in the dance bar down in midtown, call you when im ready?

[gtwirges]

Tried the sandpaper thing and the flux trick. Neither worked. This was a newer batch of CTS pots and the first time I've ever had that problem (been soldering 30+ years) I use good solder (Kester) and a good iron (Weller) and these pots just stumped me. Previous batch of pots did just fine.

Thanks,

GW

[Leo_Gnardo]

Yes you can save a lot of hassle by going the bus bar route. Many currently made pots can't easily accept solder, for the reasons Miles mentioned (reeltarded). Also, there's the matter of modern "safe" lead free solder which is a major PIA, and undersized soldering irons. Dinky 15-25 watt irons can't really handle the task. 35 to 50 watts, now we're able to heat a pot cover up enough, and the larger the tip, the better the heat transfer. Good ol' fashioned 60/40 or 63/37 tin-lead solder like Kester or Ersin work well, and sometimes you need a little help from a dab of solder flux but avoid the acid type flux which will corrode metal over time with its residue. All the above holds whether you're soldering to pot covers or bus bar. All you will get with dinky irons & unleaded solder is frustration.

FWIW there are some CTS pots currently available that do easily accept solder. I get 'em thru Antique but I'm sure they're available at other vendors too. It's always smart to scrub the surface you're about to solder to with fine sandpaper or a wire brush. Always easier to solder to fresh clean metal.

[drew]

What's the best alternative to soldering to the back of the pots if you're talking about the pots in a guitar instead of an amp?

[M Fowler]

What's the best alternative to soldering to the back of the pots if you're talking about the pots in a guitar instead of an amp?

Use this device plus internal star washer to keep it tight to pot and run ground bus.

Amphenol 31-759 .390"

The other has internal star washer already.

[Bob S]

I don't solder to pot casings any more. If you must have a buss bar, there are easier & more effective ways. I don't use pot lugs either.
I won't mention the effects of nuking a pot body or ground loops.
Some guys have good success using these methods. Not for me though.

[Leo_Gnardo]

The other has internal star washer already.

A- HAH! That's something I've been looking for. Where do you find 'em? Thanx in advance.

[KellyBass]

I've had a terrible time soldering to the back of pots, especially PEC's which I'm using on my current build. I am bound and determined to find a better way! I located a few of those ground lugs at a surplus electronics store, but they had a sort of solder tab instead of a hole. I'd like to find some hole types and try them. I'm tryin' something new this time around by soldering two together to make a platform of sorts...to support, and solder to, the buss bar. Kind of goofy but I'm desperate...

[sliberty]

Right or wrong, I always grounds the appropriate pot lug or resistor to the back of that pot. I use my Dremel to scuff up the area where I want to solder and remove the coating. With Alpha pots, this technique has never failed to provide an easy and secure solder surface.

[sluckey]

I'm not fond of soldering to the back of pots. I do like to have a buss bar running close to the pots though. This is the method I use most often these days. Here are a couple more recent examples...

http://home.comcast.net/~seluckey/amps/ ... g_guts.jpg

http://home.comcast.net/~seluckey/amps/ ... 02_big.jpg