Chris Isbell wrote:
On Tue, 19 Jun 2007 13:31:00 GMT, (Don Pearce)
wrote:


I always found that for making low signal measurements on tubes it was
a good idea to supply the heater from a battery. Did away with all
sorts of mains hum nasties.

No good for a final design, of course - but that's another question.


Agreed. A lead-acid accumulator is much better. ;-)

This brings back fond memories of my Beethoven Portable radio. This
had valves to die for and was powered from batteries - one for the HT
and a 'grid bias' battery which supplied around five different
voltages.

The output valve had a terminal on the top (from memory, the anode) in
addition to the terminals at the base. It was around 15cm tall.


Thats annoying, I am now trying to find what the battery output valve
was with a top cap.

I am thinking of the likes of PT15 or 807, but neither of those are
"battery" valves.

--
Nick