Arfa Daily wrote:

"Eeyore" wrote
Arfa Daily wrote:

A new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think
that I can remember ever having had an open circuit screen grid.

Can't say I have either. But then again have you ever seen 4 output valves
go zero emission (this was in a Fender Twin Reverb). They were those
dreadful
Z&I Aero Services (Zaerix) Russian valves from the 70s/80s. Quite bizarre,
all
drive waveforms and bias voltages correct but no output at all.

Incidentally I got it working because it was needed urgently by fitting 4
EL34s (I didn't have any 6L6s - you didn't see them much in the UK in those
days).

Graham

Yes Graham, I too have fitted 6L6's and vice versa. I have read on Wiki I
think that EL34's turn up with 6L6 guts in them. I think that the beam
tetrode structure was actually created to get around the patent that MO had
on the EL34 pentode structure

I think you're right about that although the patent would have been on the KT66
I think. MOV never made the EL34 AFAIK.


so I guess it's reasonable that they should
have similar characteristics. Crikey ! Z & I Aero Services aka Zaerix. That
takes me back a bit. I still have a Zaerix shortform catalogue in pristine
condition. Had some useful data in it, and ex military valves and 'scope /
radar tubes ...

I recall their shop in Tottenham Court Road too. You could still browse surplus
equipment back in those days. Imagine what those properties must be worth now !

Graham