RadioBanter - View Single Post

June 17th 06, 04:30 PM posted to rec.audio.tubes,rec.radio.amateur.homebrew

flipper wrote:

On 17 Jun 2006 05:42:10 -0700, wrote:

One thing I want to eliminate as a possibility is that something in my
homebrew amp did this tube in after just a few dozen hours of service:
390V on the plate, 255V regulated on the screen, about -23V on the grid
to give 38mA idle current, all following the classical AB1 parameters
in the 40's vintage tube manuals. This is MUCH relaxed compared to
typical ham transmitter usage I've done with 807/6L6GC/6146's in the
past (which is 700 to 750V B+, 80 or 90mA plate, class C so substantial
grid current, etc.) but that was ICAS.

I've got a 6EM7 that does the same thing and it's visual appearance is
perfect as well so I doubt it's your circuit.

Ironically, it turned out to be fortuitous in my case because I was
testing a circuit design intended to force PP current balance and that
tube was a great test subject. Dern thing works even though it would
run away on it's own.

A servo presumably ?

Graham