Re: Tube amp kept blowing fuses - Why?

Dave schrieb:
Phil_S wrote:
"Dave" <no@xxxxxxxx> wrote in message news:h5dni3$rvj$1@xxxxxxxxxxx
Stephen Cowell wrote:
When one goes *zorch* the other's
not far behind it. They're normally
sold in pairs anyway... and what do
they cost, $10 a pair?
EL84s are $10/pair? I didn't think any tubes were that cheap
anymore.
You can buy Sovtek for $16/pair.
http://www.boiaudioworks.com/EL84
I don't want to speak for Steve, but I belive he was generalizing to
make a point, not actually quoting a price. I have a feeling, if you
hunt around or buy in any sort of quantity, it wouldn't take much to
get the price down. Back to the point...replacing the pair is way
less hassle than continuing to blow fuses. Fuses also cost
something, as does your time. Keeping one is penny wise and pound
foolish. It would be a different case if you were dealing with
vintage cork sniffing stuff that's made of unobtanium.

It occurs to me that perhaps the amp in question might be a single-ended design. That being the case, if one tube goes, the other one has probably taken a beating too. So replacing them both is probably wise.

However, I just spoke with the friend I used to work for, and he verified that in a push-pull circuit, it's not imperitive to replace tubes in pairs. Just because one fried, it doesn't mean that the other one has been damaged.




"Normally" you fit a pair of tubes - at least in the beginning - if they are brandnew and you exactly know the failure mode and the consequnces of the failure for "neighours", you get one replacement. If that's not the case, change the set.

Do you change the wheels of your car one by one?

Let me guess: if you've got a brand new set of tires with only a few miles on them and you drive one of them flat - beyond repair, you'll get a matching one. If you got old tires and one of them disintegrates in a mysterious way (e.g. it looses parts of the rubber), would you just change one of them? Would you still trust the remaining ones?

My bet is no; you think - *** happens, i would have bought them anyway, just not that early.

Jochen
.

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