professormudd wrote: ↑Tue Dec 08, 2020 6:57 pm
Would it be worth keeping an eye out for filament flash as an indicator that you have a tube that is gonna have a shorter life?
Well that's the claim being made, that tubes with filament flash will on average have a shorter life span, presumably because the tungsten wire at some point will burn up or open.
I'm not aware of that claim being substantiated though. It doesn't seem to be that rampant of an issue, otherwise you'd assume it would be more frequently discussed.
I'm not buying it. If Telefunken, Amperex, and Mullard ECC83's were burning up they wouldn't be so desirable (at least in some quarters.)
I watched that YT again. Between about 0:46 and 0:59, he says that they bought some "...palates of large vacuum tubes..." I take this to mean they were not the preamp tubes we are so fond of. I don't think you can generalize. I see the flash he shows us. I'm sure it's real. The question is whether it is consequential. I suggest it is not. He does, however, provide the solution to the problem. It looks cheap enough. If you have doubts, go for it.
European E-series tubes are intended for a parallel heater supply and many of them have a bit uneven filament warmup and they flash. Only case where it matters is if you connect several of them in series and that's why datasheets usually say a current limiting device must be inserted in the heater supply if series supply is used.
Guitar amps rarely use a series heater supply. Only examples I can think of are Peavey amps but I doubt anyone would put expensive European old production tubes to an amp that costs less than the tubes.
Phil_S wrote: ↑Tue Dec 08, 2020 8:05 pm
I'm not buying it. If Telefunken, Amperex, and Mullard ECC83's were burning up they wouldn't be so desirable (at least in some quarters.)
I watched that YT again. Between about 0:46 and 0:59, he says that they bought some "...palates of large vacuum tubes..." I take this to mean they were not the preamp tubes we are so fond of. I don't think you can generalize. I see the flash he shows us. I'm sure it's real. The question is whether it is consequential. I suggest it is not. He does, however, provide the solution to the problem. It looks cheap enough. If you have doubts, go for it.
You're reading more into what I'm asking than what I'm actually saying. I just want to know why it happens. It's clearly not a huge problem in receiving tubes.
I'm not necessarily agreeing with the video, that we should all start implementing current limiters in our amps.
Trust, if there was a time to be skeptical of claims being thrown around, it's right now.
I don't have an answer to why, but I'm guessing there is some degree of truth to this, however overblown. I have watched a lot of his video's and built some of his projects. Carlson is one of the fussiest dudes on the planet, so, more than a few tubes failing from heater flash would be an unacceptable design flaw to him, even if it is exceedingly rare. I made his cap leakage tester, all very tiny smd parts, and didn't get it to work at first. Turns out his design had such tight tolerances that any residual flux on the board would make it inoperable. Didn't think to mention that on any documentation, other than deep on a help thread. To someone with such unnecessarily exacting standards, a potential fault like heater flash isn't ok and is something that would probably keep him up at night.
