Grounding for new build (BF Princeton in a VChamp chassis)

[centervolume]

Greetings all!

Wrapping up a build aimed at clean PP design in a smaller package. Ditched tube rectifier for SS and used an oversized OT to maximize clean power.

Everything is wrapped up except for the grounding scheme. I have had good results with larger builds but this is the smallest amp I've tried.

I'd like to get input on my approach before I commit. Here's the plan with a couple of questions

1. PT center taps for heater and high voltage windings soldered to chassis interior next to PT mounting studs.
2. Power Supply cap can has an neg terminal, not sure about best location (direct to chassis, with center taps or separate?)
3. The bias board and AC ground to one of the 4 PT mounting studs via a grounding lug that fastens along with bolt, lock washer etc
4. My main question is about the need (or not) to make a brass grounding plate. It strikes me that pots and input jacks all benefit from this common ground. Is it a
     matter of convenience to also use that same plate as a grounding buss for the two 12ax7 cathodes as well? As a matter of best practice when grounding
     potentiometer terminals, is there a benefit to using the plate versus grounding the lug to the body of the pot itself?
5. individually grounding 6V6 cathodes directly to the chassis next to pin 8 of each power tube.

It appears that the brass plate style buss from the original design comes into play on all vintage fenders larger than the tweed princeton. I infer from this that designs with only 1 or 2 pots, the brass plate is not necessary; but 3 or more pots present enough complexity to benefit from a shared brass plate grounding system.

[Colas LeGrippa]

Ac gnd to chassis, alone, with lug and locking washer , scrape off metal from chasdis with screwdriver or other tool for better contact


Center taps and filtering caps gnd same place is good


Gnd bus connected to input jack gnd (not isolated jack) and ONLY connected there. All the grid leaks, dividers and cathodes from preamp connected to that bus


Cathodes from powertubes individual or  tied together do not matter , near of them , for neat look and less wire

[Colas LeGrippa]

If you solder the gnds to the chassis, BE SURE the soldering is well done. I prefer the lug and washer, I don t like working with too much heat.
Once the soldering is done and all the components are in place, it is an hassle to modify the soldered gnd.
Have fun !


Colas

[sluckey]

1. PT center taps for heater and high voltage windings soldered to chassis interior next to PT mounting studs.

Is that chassis made of aluminum?

[Colas LeGrippa]

Aluminum no prob. Just get you a TIG welding machine

[Papa Jim]

Aluminum no prob. Just get you a TIG welding machine

He's gonna come lookin for you after he buys it and finds out he can't weld his steel or copper crimp terminals to aluminum. 

[Colas LeGrippa]

He oughta get aluminum wires of course !

[st]

If you solder the gnds to the chassis, BE SURE the soldering is well done. I prefer the lug and washer, I don t like working with too much heat.

Agreed. Go with lug and washer in an ALU chassis and in a steel chassis if you don't have a high power soldering iron. On the other hand, if you do have a high power iron, use it. It's quicker, easier, and more effective than a lug.

[bmccowan]

I recently completed a 6G2 Brownface Princeton, so thought I'd chime in.
Steel chassis and tube rectifier.
No brass plate. A 2x32 cap can, and a discreet 20uf for preamp filter.
I made a preamp ground bus soldered only to the input jack and soldered all preamp grounds to it, including the preamp filter cap.
I bolted a star ground near the PT (I did not use one of the PT bolts, but have done so in the past) and brought all the remaining grounds to this point, including the CTs, power tube cathodes, cap can, and the bias ground.
I'm not suggesting that its the best way, or that you do it this way. But it is very quiet.