Amp Chassis Earth/Ground points

Haych

So my high power Princeton build is coming along quite nicely, I think I have everything wired up right (time will tell, right) and I've got to the point where I need to connect all my earth wires to the chassis.

There's a copper plated threaded stud inside the chassis designed to take the ground wires but I have quite a few of them and I doubt it's going to be able to take them all.

In total I have:

• Reverb earth.
• Earth from pin 8 of the output tubes.
• Power transformer earths.
• IEC Earth
• Earth from the bias board.
• Earth from the cap can.
• 20pF capacitor that I need to earth somewhere (the copper grounding stud just happens to be in the perfect location).

This might seem like a stupid question but does it matter where I connect the earth wires to the chassis?  Could I use the studs that mount the PT to ground a few - they're all going to 'connect' after all, or will it potentially make the amp noisy if the earths aren't in the right place?

Also, while I'm here, it's it better to solder the earth wires to the chassis or can I use crimped eyelet connections to bolt them down, or does it not make any real difference - whenever I use the crimped connections for anything I tend to solder afterwards to avoid anything coming loose.

Apologies for the daft questions and thanks in advance.

BahHumbug

I’m sure someone with far more experience will rock up, but AFAIK, you definitely want the IEC socket attached the the chassis earth lug.  Aside from that very important safety thingy, the rest of the earth scheme needs careful consideration to avoid noise.

Here’s an admittedly long read that may help.
http://www.valvewizard.co.uk/Grounding.html

springhead

^^^  Merlin's guide is good.  And yes the safety earth from the IEC socket needs to be on it's own to a bolt on the chassis.  Use a crimp connector with solder on top and a shakeproof washer. 

I believe using transformer bolts for a safety earth is now illegal for commercial equipment, as well as bad practice.  Transformers being big heavy things can work loose, or at least enough to weaken the electrical connection to the chassis.

ICBM

Yes, for regulations compliance the IEC earth must be connected to its own separate stud/bolt with nothing else using it. If the pre-fitted one is near the socket, that's what it's for.

It's normal to ground everything else via an eyelet tag on one of its own mounting bolts or whatever the nearest convenient one for another component is, using the whole chassis as the ground. Make sure you use a shakeproof (star) washer on each one, which bites into the metal and guarantees a better connection.

You can occasionally get problems with not bringing everything to single ground point, but not commonly.

Haych

Ah, great.  Thanks everyone, that's really helpful.

The copper stud actually isn't very close to the IEC socket (but not that far, either) - it's right next to the furthest inboard PT mounting stud.

Nevertheless, I'll use that one for the IEC ground and find convenient locations to earth everything else.

Thanks again!