Re: Regulation for Filament Voltage on 833A Tubes

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

Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

OH NO!

If i were you, i would do what i did ;)  I opened up the filament 
transformer that i had and removed enough secondary turns to get my voltage 
at 10.2V when my house voltage is 130v (sometimes my house is up to 140V!!! 
and sometimes at 120v, its goofy around here).  But at 120V from a variac, 
my transformer makes exactly 10.00V.  Of course you can use a variac, but 
im my case, i only had one at that time.  So i needed to modify my 
transformer.  Yes, 11.6V is very bad for the tube!  The spec sheet is not 
being overly conservative.  Chances are, you could run the tubes at that 
voltage, but not nearly as long as they would last at the 10v they were 
designed for.  By the way, running a tube at a higher voltage will actually 
increase its output:), but dont get any stupid ideas.  Save that test for 
old tubes that are basically dead anyway ;)

Steve Ward


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Regulation for Filament Voltage on 833A Tubes
>Date: Wed, 21 May 2003 11:22:44 -0600
>
>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
>