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I have been using new quad Svetlana (Winged C) KT88 in my Jolida 502B for about 1 month. Today, after 5 minutes play, one of those tubes showed bright flashing light for few seconds and the amplifier turned off by itself. I had to change the burnt fuse in the back of the unit and now the system works again. This is the first time happened with these tubes. Is this an indicator that something wrong with one of the tubes? Should I replace with new tubes? I bias to 50mV (manual recommendation: 45-55mV)
Anybody had same experience?
Follow Ups:
I had the same problem about a year ago with a quad of VA KT88s.
It flash and blow the fuse, After replacing the fuse I use the tubes for about another 200 hours with no problem.
I change resistors and now am using the Svenlana EL34s.
Much better sounding tubes in my system.
I have been using my 502B for months now with no such problems.
I have used three different types of power tubes.
Did you replace the fuse with the same size that came out?
My 502B came with a fuse rated higher than the manual states.
I am not home now so I can't check actual sizes but I replaced the one that came with the amp with one a little smaller than the manual states.I would be very much concerned about anything that blew a fuse.
Might check the seating of the tubes.
Hopefully you'll get more knowledgeable answers as I am new to this.
I replaced it with the same fuse. Called Jolida and they recommended 6.3 fast blow fuse.
I replaced the original 6.3A 250v fast blow fuse with a 6A 125v fast blow from Lowe's.
It has been working fine for months now.
Regards, Jerry
Checking the tube seating is a good suggestion. If one were in there wrong you would most likely encounter your symptoms. Certainly the blown fuse...
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