Modern EL34 reliability?

[Enzo]

Except for New Zealand and Australia, when you drop tubes there, they fall up.

[Helmholtz]

Diablo, you are probably correct, but insofar as you quoted me, I have to point out I didn't mention g1. My surmise - and it was only that - involved g2 and g3.

They add that the G2 and G3 are not exactly aligned.

I can't find this remark about G2 and G3. Rather this:

"Plate power dissipation of EL34-B can reach 30W, whereas EL34A is 25W. EL34-B belongs to tetrode
tube compared to pentode tude of EL34A. g1 and g2 of EL34-B is not exactly aligned opposite to each
other and it is used in linear power amplification."

[Enzo]

Perhaps then I misread it, I'm not going to look it up again. If I erred, then I erred.

Seemed to me when I read it, regardless of which grids it was, they were implying that the misalignment of the grids was why they had to consider this pentode as a tetrode. At least that is what went through my mind.

[bea]

If the EL34B actually was a tetrode and behaves like a KT77, why not call it a KT77?
(IMO, the KT77 is the more advanced design.)

But to which degree can the REALLY be used as EL34 replacements? The old datasheets state a few significant differences:

a) smaller grid leak resistances for tubes under full load (=> replace the 220k in a Dynacord Eminent by 180k).
b) larger bias voltages. Or does that hold for 6CA7s
c) a maximum of 300V on G2 unless the KT77 is run in UL mode.

Did anyone try one of those?

During the last years there still was a source of NOS Svetlana Winged C and even old RFT tubes in Germany - but they seem to be mostly sold out. Which is a pity because my G-2000 urgently needs new tubes.

And the RFTs - despite being of good quality - may also have their problems. I am just confronted with one that become a little bit gassy (the getter can still compensate, at least nearly) but still works just fine under 750V.

[diydidi]

For me, its JJ's. I buy them from CE distribution. When I do use them, I always make sure the screens are 2k2 5W, and add 3000V flyback diodes to the plates.
Never had an issue!

[Gtr0]

I was having A LOT of EL34 woes a year or more ago... until I switched to Watford Valve tubes... their 'Harma' brand retros specifically - which I think are Tung Sol EL34xxxx (B-STR? or something like that). They apparently put them through a process for testing and matching - but ever since using tubes from their supply I have had ZERO issues.

Then again, I seem to have had issues with more specific suppliers... One of the suppliers I buy from I end up getting a fair share of noisy 12ax7's and have had lots of EL34 failures... Never an issue yet with using Watford's branded Harma valves... 12ax7 (balanced and unbalanced), EL34, and 5881. I have them in no less than 5 of my amps currently.

A bit more expensive, but so far worth every cent.