Grounding dilemma

[Coastie99]

I'm building a low-power practice amp. and would like to star ground it by soldering to the chassis.  Sounds easy when other's mention it ....... aim enough heat at the spot and melt a puddle of solder.

However, my soldering iron doesn't have the necessary horsepower and I'm unwilling to spring for another.  Additionally, I read about difficulties involved in applying solder to aluminium.  

I'm wondering, if it isn't technically a difficult job, would one of those butane torches be the ideal heat source ?  Or, should I simply bolt my ground to the chassis, as I've previously (carefully) done ?

I read also, somewhere, that leaded solder is unsatisfactory for this purpose ??

Thank you,

Gary

[John]

From what I've read here and elsewhere, it's best to bolt down your ground points instead of attempting to solder.

[kagliostro]

If you have an alluminium chassis, to solder to it, you must use a special metal alloy

better to bolt down

Kagliostro

[stratele52]

Yes bolt on with lock washer or something like that will make a perfect connexion.

Famous Dumble amps are made with standard ( IMO ) aluminium Hammond chassis.

[HotBluePlates]

However, my soldering iron doesn't have the necessary horsepower and I'm unwilling to spring for another.  Additionally, I read about difficulties involved in applying solder to aluminium.  

If you need to solder to a steel chassis, I'd recommend you use a 100w iron (bare minimum 60w, which will probably still not work). If you can't make the chassis hot enough to melt the solder (not melted by the iron itself), you will get a joint that looks good but will pop off the second you flew the wire.

Are you trying to solder to aluminum? Don't waste your time. You can weld aluminum, with special techniques; even a 100w iron won't be close to hot enough. And yes, it would take a special alloy. Regardless, if your chassis is aluminum, bolt your chassis ground.

[eleventeen]

Soldering aluminum requires "aluminum solder" which you can buy. It typically produces a pretty grainy looking blob of solder which is not very satisfactory.

If you need a big-heat soldering iron to solder to a steel chassis on a one-time basis, you can simulate same by heating up a bolt in a Bernz-o-matic propane torch. Hold the bolt in a crappy pair of pliers or vise-grip with the bolt head "out" = exposed. The pliers grip the threads. A 1/4-20 bolt is ideal, and galvanized or zinc plated is better than raw black iron. A brass bolt would also work fine. Do not overheat a cadmium-plated bolt! 

Scrape a piece of shiny metal on the chassis with a knife blade, then jam the heated bolt against the chassis. You don't have to get the thing screaming red-hot, just "hot". Should solder quite readily. Tin the wires you wish to incorporate into the eventual solder joint, and do the same thing with the bolt with the tinned and positioned wires. You can't do this in super-tight quarters nor right next to a heat-sensitive component. But you can make an absolutely credible looking solder joint this way.

[Coastie99]

Thanks for all the responses guys, and the great advice you've given.

Looks like I'll be bolting my grounds !

[Fresh_Start]

A couple of thoughts re: bolting grounds.  Scour the metal on both sides around the hole with sand paper and make sure it's free of oil/grease/dirt/paint to get best contact.  I put a lock washer under the screw/bolt head on the outside of the chassis, another immediately inside the chassis and then a 3rd between the ring terminal(s) and the nut.  I want as much metal-to-metal contact as possible with the lock washers biting into the chassis.

Cheers,

Chip

[stingray_65]

  I want as much metal-to-metal contact as possible with the lock washers biting into the chassis.

+1 to all that Chip.

I do go one step further, instead of a through hole, I tap my ground lug mount hole.

Ray