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I've have a Marshall Super Lead on the bench, turned it off standby and one EL34 flashed (bright blue-white, def. an arc). Turned the standby off for a few seconds and back on, and two of the tubes flashed (not at the same exact time).
The tubes in the amp are newer Chinese Valve Arts EL34s 'apex matched' from CE/AES, probably not original. I've had fairly good luck with these to date.
I know once they've flashed, they're done, and are more likely to flash going forward, but what causes the initial flash-over from plate to screen/cathode/whatever? A big voltage surge perhaps, like unplugging the speaker while playing loud? Or perhaps cranking it with no speaker attached? I have no history on the amp, but it has a 2015 S/N, is in like-new condition, and definitely hasn't been gigged.
The tubes in the amp are newer Chinese Valve Arts EL34s 'apex matched' from CE/AES, probably not original. I've had fairly good luck with these to date.
I know once they've flashed, they're done, and are more likely to flash going forward, but what causes the initial flash-over from plate to screen/cathode/whatever? A big voltage surge perhaps, like unplugging the speaker while playing loud? Or perhaps cranking it with no speaker attached? I have no history on the amp, but it has a 2015 S/N, is in like-new condition, and definitely hasn't been gigged.
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