Re: 833A's plate color

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Shad <shenderson@xxxxxxxxxxxxxxxx>

Hi All,

I need to disagree here a little bit.

Some tubes, such as the 300Z, use a graphite plate and *must* show plate
color for the getter to act properly.  Most tubes that use a graphite
plate don't have a getter flashed in the tube.  Instead the getter is
applied to the plate, and the getter must be hot to work.   Not running
any plate color on a 300Z is one of the quickest ways to kill one, as it
is with almost any large graphite plate tube.  Graphite plate tubes also
tend to have a much higher thermal inertia than the thinner metal plate
tubes, making them more able to withstand short-term abuse as far as
plate dissipation goes.
  The 833C is just such a tube, as it has a graphite plate.

 I've pushed an RS1026 (300W p.diss graphite triode) to 4kW input for
3-5 second runs.  Graphite plate gets bright orange, but no harm to the
tube.  (Tank capacitor did fail though...)


I recommend the RCA TT-5 book, as it cover transmitting tubes up to 4kW,
and is a variable wealth of information on the care and feeding of
tubes.  There's usually copies floating around on eBay.

On Sat, 2006-03-25 at 10:49 -0700, Tesla list wrote:
> Original poster: "Henry Hurrass" <dr.hankenstein@xxxxxxxxxxxxx>
>
> I think the suggestion that a power tubes' plate is supposed to glow a
> "dull red" during normal operation is ignorant. If the plate is glowing,
> the plate's maximum dissipation is obviously being exceeded and the life of
> the tube(s) will suffer due to, in part, the following factors:
>
> Plate voltage too high.
> Grid voltage too low, (too small value grid leak resistor in tesla coils),
> causing excessive plate current to flow.
> Plate circuit out of tune.
>
> Of course, it is tempting to observe and enjoy the longer spark that occurs
> when we "max out" the plate dissipation of our transmitting tubes; but
> remember, you are exceeding the maximum design parameters of the tube(s).
>
> If you want your tubes to last for years, I would never advocate running
> them with any kind of 'glow' other than the filaments. This is good just
> plain good design etiquet. But thain again, they're you tubes, so if you
> want to run them in 'supernova', be my guest. Just remember what others may
> be thinking when they watch your TC's plates overheating.
>
> Dr. Hankenstein
>