What do you think causes pins 2 and 3 to arc in octal sockets.

[Mark]

I use ceramic sockets in my builds as I try to avoid the 2 to 3 arc over. None of my amp have had this fault and my wiring is always tidy. I have accidentally switched on an amp without a load but I have yet to see this turn into a fault. I’m not saying it won’t happen, it just hasn’t happened yet.

I saw this on one of the octal valve sockets, I’m not saying this is the case with all sockets, just this one. I have pushed it up as I can’t pull it out though it was across the socket reaching for pin 3.

IMG_0284.jpeg

[jabguit]

Regular maintenance cleaning of the socket surface between pins 2-3 with IPA is well worth it to manage 'pollution' build up that can lead to reduced creepage and clearance, and then tracking/arcing.

Would a regular pale ale suffice?
Asking for a friend.........


cheers,

[Stevem]

You can run any amp with a tube output stage with no load on it and suffer no problems, just don’t pump any signal thru it!

[martin manning]

I always connect a load when the output tubes are installed. If an oscillation starts, the amp will create its own signal.

[sluckey]

There's not always a visible arc trace between pins 2 and 3. Sometimes the arc simply happens inside the tube. There may be another telltale sign that pin 3 has arced to pin 2. If the heater circuit has an artificial center tap (Fender liked to put two 100Ω half watt resistors on the pilot lamp assembly) one or both of those resistors will most likely be blown.

[GAStan]

I always connect a load when the output tubes are installed. If an oscillation starts, the amp will create its own signal.

Truth. Unfortunately I have a pretty new matched quad of 6L6's with at least one bad tube from this very thing.

[FUCHSAUDIO]

Maybe manufacturers like FUCHSAUDIO will start retrofitting a suitable MOV across each half-primary as a simpler and more direct way to mitigate such faults.

It's not a substantial expense in production, although we never did it in 20+ years. We rarely get amps back with this type of failure. Hate to say "Leo never did it", but he didn't.
Traynor and Ampegs did at various times. You'd really need to do some serious a/b testing in the real world to make 100% sure it's a worthwhile addition to an amp, although I don't know of any "downside".

Food for thought.