Is there any benefit in a grounding bus across the back of potentiometers?

[tubedood]

Hi again everyone!
I have found very mixed info on various forums regarding peoples thoughts to running a bus wire across the potentiometer backs for grounding purposes. I was originally going to run one across the volume and tone pots on my 5F2-A and end it on the input jack ground lug, which then would drop a wire to the V1A cathode grounding point and across the preamp bus... Now I am not sure if the bus across the potentiometers invites more problems than it solves? Maybe on the high gain amplifiers this helps but would I see any benefit on a little Princeton?


Dale

[Randall]

The ground bus wire does nothing if it is soldered to the pot backs, they are already grounded to the chassis. The idea is to fly it away from the pot backs, and tie all preamp and pot leg grouds to the bus, then ground the bus wire to the input jack ground, or near it, That way everything gets it's ground reference at the same point, away from the HV grounds.

[Leo_Gnardo]

Show him that picture of the inside of your Deluxe Reverb Randall, that's what a ground bus ought'a look like.

[Randall]

Here it is. I wish I had taken a more detailed shot, but this is what I could find.

[tubedood]

Wow thank you so much for sharing that photo Randall!
Very nice amplifier and gives me a few insights on both the potentiometer grounding and also the heater wiring.
Much Appreciated!
Dale

[mozz]

What is supporting that buss bar in the picture? I have used the back of the pots to run a ground bar, maybe 18-20 gauge solid, tie whatever is closer or a pot that needs a ground. No hum. Only downside is you may damage a pot if you get it too hot, i crank up the temp on the Weller WESD51 get in get out.

[tubedood]

Randall's amplifier looks sweet... Fender at least on the 5F2-A didn't focus much on grounding the potentiometers other than the "bite" of the fastening hardware? I was planning as mozz has said to run the 20 gauge bus wire across the potentiometer backs to one of my input jack ground tabs, then drop a wire to the V1a cathode point on the board then across to the 10uf capacitor I am using for the preamp plates.
Hence my question, there looks to be many tips and advice on the grounding of our amplifiers! But I have read as mozz states the less time on the potentiometer backs with a hot iron the better. Hot and quick!

[Enzo]

The bar in the photo is supported by the wires soldered to it.

In the days of the old Fenders, pots were most all metal, and grounded well by the mounting nut, especially when a star washer was on the bushing. That tended to ground the cases. Now days we cannot count on the case being continuous metal to the bushing. SO soldering a grounded bus wire to the pot cases grounds them, they act as shields for the innards.

[mozz]

I see nothing supporting that buss bar, it can sag. Looks like a piece of brass or bronze rod, much heavier than even a 14 gauge wire which would be overkill. Would not want that weight directly attached to the pot lugs as shown.

[g1]

If I went to replace a pot, and found a big buss bar connecting it to all the other pots, I'd be perturbed. But maybe I'm just getting old and cranky.

[The Dude]

You don't have a big side cutter?

[g1]

As a matter of fact I do! We don't call them that though.

[Randall]

"I see nothing supporting that buss bar, it can sag. Looks like a piece of brass or bronze rod, much heavier than even a 14 gauge wire which would be overkill. Would not want that weight directly attached to the pot lugs as shown."

It's a piece of #6 copper wire suspended by a mixture of 13 soldered connections of 18 gauge filament wire and 1 watt resistor legs. There is neither sag nor stress to anything. Actually, it's very sturdy indeed. You couldn't move it if you wanted to. I haven't tried it, but I bet you could lift the chassis with it. It may seem overkill to some I suppose, but it works very well. I have made two of them this way.

[galaxiex]

"I see nothing supporting that buss bar, it can sag. Looks like a piece of brass or bronze rod, much heavier than even a 14 gauge wire which would be overkill. Would not want that weight directly attached to the pot lugs as shown."

It's a piece of #6 copper wire suspended by a mixture of 13 soldered connections of 18 gauge filament wire and 1 watt resistor legs. There is neither sag nor stress to anything. Actually, it's very sturdy indeed. You couldn't move it if you wanted to. I haven't tried it, but I bet you could lift the chassis with it. It may seem overkill to some I suppose, but it works very well. I have made two of them this way.

Nice!

I think it is very robust looking.
Has a look of solidity about it.