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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
roberjerman
4,319 posts
 
A shorted tube. Check the fuses! Hopefully they will blow before any major damage is done (fried resistors and blown caps). Open the bottom cover and look for damage (fried parts). If everything looks good and the fuses are intact you can replace the dead tube with a known good one and try turning on the amp. Be sure to have a load (speaker or power resistor) connected! If the fuses are blown you can try replacing them - but ONLY if there is NO sign of damage! If on turn on the fuses blow again you will have to bring the amp to a competent tech for further diagnosis (shorted power or output transformers). 
roberjerman
4,319 posts
 
It is always good to have spare tubes on hand for quick replacement. Current production tubes DO NOT have the longevity of past production (pre 1970's)  Meaning that they (power tubes) cannot safely handle higher plate voltages. 
roberjerman
4,319 posts
 
Buy old production USA, UK, Holland, German, Japanese tubes whenever possible for longevity AND sound quality! Avoid the rest!
ddzstereo
84 posts
 
For my last retube I used Winged C Sed 6550C tubes and had 1 of 16 fail after a couple of hundred hours at most.  Subsequently I have learned/been advised exactly what roberjerman has said "Current production tubes DO NOT have the longevity of past production"
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