Re: Regulation for Filament Voltage on 833A Tubes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Sharpe by way of Terry Fritz <teslalist-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>

Dan
I'd either use a small variac, or put a 25W Rheostat in series with 
transformer primary to
drop the line voltage about 5-10%.  Filament life is a inverse fourth power 
function of rated
voltage (i.e. 110% nominal filament V = 68% "nominal" life.  Emission is 
increased signifcantly
as well so may be worth the trade off.  I'd opt for a 3A variac and adjust 
at socket with tube
to rated value...

Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA

Tesla list wrote:

 > Original poster: "Mccauley, Daniel H by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
 >
 > I finally got my 833A VTTC up and running and I noticed that the actual
 > filament voltage coming from my
 > 10V, 10A filament transformers is about 11.6 VAC.
 >
 > The nominal spec for the 833A tube is 10V +/- 0.5V  (either AC or DC).
 >
 > Common sense always says you should abide by the datasheet and that
 > exceeding this limit would either be destructive to the tube, or reduce
 > optimal performance.  However, I have very limited experience with vacuum
 > tubes so I don't know how critical
 > this actually is.
 >
 > What are your thoughts?  Okay as is, or do I need to control this precisely
 > via variac???
 >
 > Thanks
 >
 > The Captain
 >
 >