March 11th, 2012, 03:21 PM
So, I'm attaching the power tube sockets to the chassis and it occurs to me that I could use some O-rings to physically isolate the tube sockets (and therefore the tubes) from the chassis for anti-vibration purposes, but then I wondered if the tube sockets need to be snug against the chassis for grounding purposes. I see now that I think about it that the sockets will still be touching the chassis via the mounting screws, but still thought I'd ask if there were any good or bad reasons to try this.
Sockets are ceramic with a metal mounting 'flange', if it matters.
March 11th, 2012, 03:33 PM
It would matter if the flange were electrically connected to some point in the tube (which I doubt).
I think the issue may be more one of heat buildup, especially for a ceramic socket as they were designed for high heat applications. A plastic socket would be even more likely to be damaged. Plus (I'm on a roll now!) isolating the tube from vibration implies introducing some amount of flex to the socket wiring which is now more likely to fail due to the vibration: tubes are really tolerant of thermal and vibration nastiness (technical term) but wobbly wiring isn't.
March 11th, 2012, 03:34 PM
As I understand it, and hopefully others will jump in with specifics...
Grounding should not be an issue. If the tube circuit requires a ground to complete a circuit, it will be through a pin, whether common ground or path-specific.
Where I have seen tube sockets isolated from the chassis is in the case of tubes that may have a tendency to be microphonic or susceptible to shock damage. I have seen instructions for builds with one type of tube isolated with grommets and others mounted solidly so it would be good to hear answers from others as well.
March 11th, 2012, 03:46 PM
Here is how Fender did it on the originals. Click on the photo to enlarge it and you can see the jumper wires soldered to the chassis.
March 11th, 2012, 04:07 PM
No, no need for the socket to have a ground connection
In this assembly, there is an O-ring between the socket and the turret board, an o-ring between the socket and retainer and o-rings between the retainer plate and the turret board. The assembly hangs from the retainer plate that is also shock mounted to the chassis
March 11th, 2012, 08:54 PM
So, no ground issues resultant of O-ring isolated tube sockets. Good to know.
What's that unit for, Celeste, an ICBM?
March 11th, 2012, 10:51 PM
It is a trainwreck like thing, but different, called a Lokomotiv. It has a pentode in the preamp, but not an EF86.
March 11th, 2012, 11:19 PM
Several of the old Sears Silvertones used rubber grommets as shock absorbers for the preamp tubes.