Soldering pots together with Bus wire.

[mightymike]

I need some pointers on technique so it will look like this.
http://www.metroamp.com/store/images/vo ... cntrls.jpg

[VelvetGeorge]

Mount them to the chassis, then solder the buss wire across the back.

You also need to scrape of the anodized (or what ever that stuff is) covering off before the solder will stick. A file or Dremel tool work for that.

george

[Guest]

you can use sandpaper too.
stan

[dynaman]

I've found a little extra heat helps. If you use a janky iron with a skinny tip the heat drains out of it quickly and dissipates through the pots casing. I've had great results with a broad tip in a 40W iron. I used the cheapo orange one from Home Depot. 40W is probably overkill so the tip shouldn't be left too long on the pot. As George said, be sure to sand off the anodizing and get down to real metal.

[mightymike]

I knew it was something simple like sanding. I will give that a try.
Thanks

[Guest]

This may me a dumb questions, but why do you need the buss wire on the back of the pots? Aren't they already grounded via the chassis?

[mightymike]

You're right they are grounded
The better grounding is to help prevent noise, and any possible ground loops.
Not grounding the pots with the bus wire would be like not putting fuse circuitry in your amp. Sure it will work without them, but it's not a good idea IMHO. There's a few wires that are grounded to that bus wire too. Like your input jacks, and 2 of the big filter caps. (The one under the board, and the one closest to V4?) If that bus wire wasn't there, those wires would have to be grounded somewhere else.

Personally I prefer extra grounding. This way if you ever have noise problems, you'll know it's not because half assed grounding.

The funny thing is my 73 Marshall didn't have those 2 caps grounded to the Bus wire on the Pot, and it wasn't noisy at all. My kit has those terminal luged to ground, and then two black wires to the lug. One wire goes to the board, the other to the bus wire on the pots.

My 2 cents

[Guest]

I have been following Randall Aiken's advice on local star grounds. See his article on his website: http://aikenamps.com/StarGround.html

Here is what he says about bus wire

What about volume and tone control grounds?
The ground connections for the volume and tone controls should not be connected to the potentiometer case, for two reasons. First, it destroys the star ground scheme and can contribute to ground loops. Second, when the nut that holds the pot in place becomes loose (and it will, eventually), you will get a bad ground connection and noise or intermittent operation. You should always solder a wire from the grounded pot connections back to the common local ground of the stage the pot is used in. For example, the grounded pin of the volume pot, if it is located at the grid of the second tube section, should go to the local common point for that second tube section's cathode resistor and bypass cap. Don't use the Fender style brass plate and connect the grounds there. The pot cases will be grounded to the chassis via the mounting nut, so they will have the benefit of shielding, but you don't want the circuit connection to go to that point.

I don't think you can make the analogy to a fuse because there is not a safety issue involved. I think the bus wire actually will create a local ground loop and would be nosier than a single local ground point. Also, I can think of a number of amps that don't use the buswire on the pots like Soldano, Komet, and Bogner just off the top of my head.

[rtcook]

I eliminated the buss wire on my JTM45 reissue project and it's extremely quiet. I too followed Aiken's and Paul Ruby's advice on star grounding. It worked out extremely well. It's much neater looking and you don't have to sand pots to get solder to stick.

Roger