Re: 833A's plate color

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "BRIAN FOLEY" <ka1bbg@xxxxxxxxxxx>

Hi, i am surprized our tube man John hasnt chimed in. first from ham radio
here any tube where the plate is beginning to show color means you are
there, some run hotter and some cant tolerate any color. on a 833 if its
showing some red that should be enough and still preserve the tube life.
another danger of going by color is that you may not have sufficient cooling
for the color you try to run and once the glass starts to cave in its all
done quickly! cul brian f.
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, March 21, 2006 6:03 PM
Subject: Re: 833A's plate color


> Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>
> Tesla list wrote:
>
> >Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
> >
> >Hi,
> >
> >This says the plates should be an "orange-red" color:
> >
> >http://www.adamhorden.co.uk/site_data/833a.pdf
> >
> >Sounds like you are running a little too much power.  But I do that
> >too for a short time ;-))  I try to be very careful since bright
> >orange is also the color of molten glass!
> >
> >Maybe someone knows if running them bright orange will decrease
> >their life to say 100 hours, or if it will decrease their life to 10
seconds?
> >
> >High voltage isolated RF current measurements are nasty.  Best just
> >to judge by the color...
> >
> >Cheers,
> >
> >         Terry
> >
> >
> >At 01:03 PM 3/21/2006, you wrote:
> >
> >>  I am running an 833A based coil.  The tube is NOS RCA from a now
> >> defunct AM radio station.  I have approx. 3000 vac on the plates.
> >>I'm getting a nice 18 - inch brush discharge, but the plate color
> >>is bright orange.  I have been told that I am pushing this
> >>tube.  Is this correct?  What should my plate /current/current
> >>be?  How can this be measured?
> >>
> >>Thanks
>     I think you're OK for the kind of operation you're doing - you're
> never going to pile up hundreds of hours of operation.  I think he's
> talking about the DC current, which can be measured at the low
> voltage / ground terminal of the transformer if desired.  By the way,
> there is a standard method for measuring plate dissipation of big
> transmitting tubes.  The temperature of the plate is measured with an
> optical pyrometer.  Then the tube is operated with DC (no RF present)
> and the grid/plate voltages adjusted to give the same
> temperature.  Under those conditions all of the power input is plate
> dissipation.  Net tube efficiency can be determined by taking the
> difference between the DC plate current during operation and
> subtracting the plate dissipation from it.
>
> Ed
>
>
>