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Flash from power tube

Brand new to tubes here. Just recently bought a Jolida 302BRC here on audiogon. Previous owner put in Winged C Sed el34 tubes. Been working great since feb, but today when I turned it on, one of the tubes flashed and the amp wouldn't turn on. Stupidly I tried again, and same result. I removed the tube but don't really know what visible evidence there would be since i don't know what to look for lol. Anyway, my question is can I just order a replacement tube? Or when replacing tubes am I supposed to replace all 4? I know they were purchased at the tubestore.com so I could easily order 1. 
jp888
wolf_garcia
6,696 posts
 
This is ruining my desire to obtain a set of "winged C" tubes, although there might be some fun in waiting for them to explode…move the furniture away from the amp and get the extinguisher ready.
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atmasphere's avatar
atmasphere
11,807 posts
 
If you buy a set of tubes that are new manufacture, its a good bet that they have not been pre-conditioned.

This is the process that essentially cures the cathode coatings in the tube.

Its done by running the filaments for several days and nights with no B+; if B+ is applied the process stops.

This can double the life of the power tube, and reduce premature arcing caused by flakes of the cathode coating (which is conductive) falling off the cathode and shorting to other elements in the tube. 
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