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I've just realised that my plan for tube protection in my next amp build uses a metal cage that is not safety earthed. I know, the chances of it being an issue are remote... but present.
I'm powder coating and would like a decent-looking finish - I'd prefer not to be masking or scratching exterior paint to create a bond - how can I ensure the cage is earthed?
My other option is to use bent acrylic, high-impact acrylic or polycarbonate, but I'd like to maintain a "classic" look.
Any thoughts?
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Follow Ups:
With screw side on underside of chassis? On bare metal spot. Like computer PCB in photo.
Good idea.Thinking while I type: The snag is that because I am using powder coat on both sides of the cage and chassis, at no point would bare metal on the cage connect with bare metal on the chassis, either directly or via the stand-off. To achieve continuity I'd need to scrape off some paint... but I guess with stand-offs, the bare metal could be on the under-side of both...
Not ideal, but a real possibility. Thanks!
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Edits: 07/18/17
I suspect most commercial cages aren't securely earthed to the chassis. The only electrical connection might be the inner circumference of the hole where the hold-down bolt passes through, and the lockwasher on the chassis. That's iffy though, and certainly doesn't create a reliable connection. Equipment that generates RF, such as a ham radio transmitter, will often have both the cage and chassis plated, rather than painted, to ensure good contact. I've never found this treatment necessary regarding audio gear.
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Buy Chinese. Bury freedom.
Thanks Tk.
Yea, in my case the hole where the hold down bolt passes through would be powder coated and a touch oversize - no guarantee the bolt would touch it.
I guess I was concerned about the cage becoming live, but that is very unlikely - it would need to be caused by a broken tube envelope or something external.
I'm probably being overly cautious and could probably just leave it float.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
The only reason you would want it grounded would be for RF shielding, but in a audio amp, not really a big problem. If you cant ground it, you probably cannot electrify it either.
If you're using bolts, why not a star lock washer between the cage and chassis?
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Thanks again all.
It would be very inconvenient because I use subchassis that would obscure access to the lock washer, if used out of sight underneath the chassis.
I may have been trying to solve a "problem" that did not exist.
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
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